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  • richardmitnick 11:27 am on July 3, 2022 Permalink | Reply
    Tags: "CERN’s Higgs boson discovery:: The pinnacle of international scientific collaboration?", , , CERN LHC, , , , , ,   

    From “Physics Today” : “CERN’s Higgs boson discovery:: The pinnacle of international scientific collaboration?” 

    Physics Today bloc

    From “Physics Today”

    30 Jun 2022
    Michael Riordan

    Decades of effort to establish a global, scientist-managed high-energy-physics laboratory culminated in the discovery of the final missing piece of the discipline’s standard model.


    Credit: Abigail Malate for Physics Today

    Ten years ago, two of the largest scientific collaborations ever—spanning six continents and encompassing more than 60 nations—announced their discovery at CERN of the long-sought Higgs boson, the capstone of the standard model.

    Physicists from all the countries involved could take well-earned credit for what will surely stand as one of the 21st century’s greatest scientific breakthroughs. It was a remarkable diplomatic achievement, too, at a moment of relative world peace, perhaps the pinnacle of international scientific cooperation. And it would not have been possible without a series of farsighted decisions and actions.

    _______________________________________________
    Higgs


    _______________________________________________
    Part of CERN’s success as a citadel of modern physics is due to the early-1950s decision to establish it in Geneva, Switzerland, a city and nation widely recognized for cosmopolitanism and political neutrality. Many thousands of scientists of diverse nationalities, not just Europeans, have eagerly pursued high-energy-physics research in this highly appealing environment, given its many cultural amenities—plus world-class hiking, mountain climbing, and skiing in the nearby Alps.

    CERN grew steadily during more than five decades of increasingly important high-energy-physics research, reusing existing accelerators and colliders wherever possible in the construction of new facilities. It gradually developed a talented, cohesive staff that could effectively manage the difficult construction of the multibillion-euro Large Hadron Collider (LHC) and its four gigantic detectors: ALICE, ATLAS, CMS, and LHCb.

    ___________________________________________________________________
    LHC

    LHC

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    ALICE

    CMS

    LHCb


    ___________________________________________________________________

    After the 1993 demise of the Superconducting Super Collider (SSC), CERN leaders decided to pursue construction of the LHC, but they realized they needed to attract significant funds for the project from beyond Europe. That transformation—effectively to make it a “world laboratory”—required extending its organizational framework and lab culture to embrace those contributions and the large contingents of non-European physicists that would accompany them.

    Given that accomplishment, CERN will likely remain the focus of world high-energy physics as the discipline begins building the next generation of particle colliders.

    Especially after the savage Russian invasion of Ukraine and the looming bifurcation of the world order, the lab now offers an island of stability in a global sea of uncertainty. National governments require strong assurances that the money and equipment they send abroad for scientific megaprojects are being well managed on behalf of their scientists and citizenry. In that regard, CERN has a remarkably robust, decades-long track record.

    Funding international collaborations

    Establishing a vigorous, productive laboratory culture does not happen overnight. It requires years, if not decades. In the late 1980s, SSC proponents failed to appreciate that essential process. Rather than electing to build their gargantuan new collider in Illinois adjacent to Fermilab and adapt the lab’s existing Tevatron to serve as a proton injector, they selected a new, “green field” site just south of Dallas, Texas.

    __________________________________________________________
    [Earlier than the LHC at CERN, The DOE’s Fermi National Accelerator Laboratory had sought the Higgs with the Tevatron Accelerator.

    But the Tevatron could barely muster 2 TeV [Terraelecton volts], not enough energy to find the Higgs. CERN’s LHC is capable of 13 TeV.

    Another possible attempt in the U.S. would have been the Super Conducting Supercollider.

    Fermilab has gone on to become a world powerhouse in neutrino research with the LBNF/DUNE project which will send neutrinos 800 miles to SURF-The Sanford Underground Research Facility in in Lead, South Dakota.]
    __________________________________________________________

    Other factors were involved in the project’s collapse, too, among them the internecine politics of Washington, DC (see my article, Physics Today, October 2016, page 48). But mismanagement of the project (whether real or perceived) by a contentious, untested organization of accelerator physicists and military managers contributed heavily to the SSC’s October 1993 termination by the US Congress.

    When the US quest to build the SSC finally ended, CERN was ready to push ahead with plans for its fledgling LHC project—and to make it a global endeavor. Whereas the SSC project had severe difficulty in securing foreign contributions for building the collider, CERN reached beyond its 19 European member states for contributions to the LHC. By the time the CERN Council gave conditional approval to proceed with the project in December 1994, the lab could anticipate sufficient funding from Europe for an initial construction phase based on a proposed “missing magnet” scheme: Just two-thirds of the proton collider’s superconducting dipole magnets would at first be installed in the existing 27 km tunnel of the Large Electron–Positron (LEP) Collider after its physics research ended. Some doubted whether the scheme was feasible, but it permitted the project to begin hardly a year after the SSC termination. And CERN then opened the door to additional contributions from nonmember states that would allow LHC construction to occur in a single phase.

    In May 1995 Japan became the first non-European nation to offer a major contribution to LHC construction, committing a total of 5 billion yen (then worth about 65 million Swiss francs or $50 million). Russia made a similar commitment the following year, mainly for the construction of the LHC detectors. Canada, China, India, and Israel soon followed suit (although with smaller contributions). The US—still smarting from the SSC debacle—took longer. After lengthy negotiations with the Department of Energy and Congress, CERN director general Christopher Llewellyn Smith finally succeeded in securing a major US commitment worth $531 million in December 1997, including $200 million for collider construction. The US, Japan, and Russia were granted special “observer” status on the CERN Council, giving them a say in LHC management.

    Russia provides an excellent case history of the negotiations and agreements involved in extending CERN participation to include nonmember states. Soviet and Russian physicists had been involved in research there since the mid 1970s, when they began working on fixed-target experiments on the Super Proton Synchrotron.

    In the early 1990s, Russian physicists made major contributions to the design of the CMS detector for the LHC, for which the RDMS (Russia and Dubna member states) collaboration, led by the Joint Institute of Nuclear Research (JINR) in Dubna, Russia, played a formative role.

    4
    Cutaway view of the original Compact Muon Solenoid, or CMS, detector. Credit: CERN.

    The total cost of materials and equipment produced in Russia for the CMS has been estimated at $15 million, with part of the amount provided by CERN and its member states. Russian institutes contributed a similar value of equipment and materials to the ATLAS experiment—again funded partly by CERN and its member states. Hundreds of Russian physicists have since been involved in both experiments.

    And those globe-spanning experimental collaborations benefited extensively from the creation and development of the World Wide Web at CERN by Tim Berners-Lee.

    By the time CERN shut down the LEP in November 2000 and began full-fledged LHC construction, the lab had effectively been transformed from a European center for high-energy physics into a world laboratory for the discipline. The “globalization” of high-energy physics was off to a good start.

    A crucial aspect of that global scientific laboratory is the Worldwide LHC Computing Grid, a multitier system of more than 150 computers linked by high-speed internet and private fiber-optic cables designed to cope with the torrent of information being generated by the LHC detectors—typically many terabytes of data daily. Initial event processing occurs on CERN mainframe computers, which send the results to 13 regional academic institutions (Fermilab and JINR, for example) for further processing and distribution. The grid enables experimenters to do much of the data analysis at their home institutions, supplemented by occasional in-person visits to CERN to interact directly with collaborators and detector hardware. In addition, thousands of these physicists make extensive use of the World Wide Web to share designs, R&D efforts, and initial results as well as to draft scientific articles for publication.

    CERN has been able to establish a successful laboratory culture, conducive to the best possible work by thousands of high-energy physicists, because the lab has essentially complete control of its budget, which exceeded a billion Swiss francs annually as the new century began. Accommodations have been made for specific national needs (for example, the costs of German reunification), but the resulting budget remains under CERN auspices. Important decisions are made by physicists—not bureaucrats or politicians—who better appreciate the ramifications of those decisions for the quality of the scientific research to be done. Contrary to the case of the SSC, meddlesome military managers were not involved.

    Discovering the Higgs boson

    Scientists’ control of their own workplace, which begins with laboratory design and construction and continues into its management and operations, is an important factor in doing successful research. When a meltdown of dozens of superconducting dipole magnets occurred shortly after LHC commissioning began in September 2008, for example, it was a crack team of CERN accelerator physicists who dealt with and solved the utterly challenging problem, taking more than a year to bring the machine back to life. Protons finally began colliding in November 2009, albeit at a reduced collision energy of 7 TeV and at very low luminosity (collision rate).

    Serious data taking began in 2011, as LHC operators nudged the luminosity steadily higher and proton collisions began to surge in. By year’s end, both the ATLAS and CMS experiments were experiencing small excesses of two-photon and four-lepton events—the decay channels expected to give the clearest indication of Higgs boson production—in the vicinity of 125 GeV. But both collaborations stopped short of claiming its discovery.

    When similar excesses appeared in the experiments during the spring 2012 run, their confidence swelled—especially after combinations of the two-photon and four-lepton events exceeded the rigorous five-sigma statistical significance required in high-energy physics. I was fortunate to be present at CERN (if a little groggy from jet lag) when that crucial threshold was crossed in late June by a group of ATLAS experimenters, many hailing from China and the US, who began noisily celebrating in an adjacent office. (See the accompanying essay by Sau Lan Wu.)

    The 4 July 2012 CERN press conference announcing the Higgs discovery—timed to coincide with the opening day of the 36th International Conference on High Energy Physics in Melbourne, Australia—was televised around the globe to rapt physicist audiences on at least six continents. Americans had to awaken in the early morning hours of their nation’s 236th birthday to watch the proceedings. In the packed auditorium, along with former CERN directors (including Llewellyn Smith) and current managers sitting prominently and proudly in the front row, sat theorists François Englert and Peter Higgs, who would soon share the Nobel Prize in physics for anticipating this epochal discovery (see Physics Today, December 2013, page 10). “I think we have it,” stated CERN director general Rolf-Dieter Heuer after the ATLAS and CMS presentations, perhaps a bit guardedly. “We have observed a new particle consistent with a Higgs boson.”

    5
    At the Higgs discovery announcement, CERN Director General Rolf Heuer congratulates François Englert and Peter Higgs, who would later receive the 2013 Nobel Prize in Physics for their theoretical description of the origin of mass—which was confirmed by the Higgs boson detection.

    It was certainly a European triumph, a vindication of the continent’s patient and enduring support of science—but also a triumph for the global physics community. Both the ATLAS and CMS collaborations then involved about 3000 physicists. ATLAS physicists hailed from 177 institutions in 38 nations; CMS included 182 institutions in 40 nations. Physicists from Brazil, Canada, China, India, Japan, Russia, Ukraine, and the US, among many other nations, could rejoice in the superb achievement, along with those from Belgium, France, Germany, Italy, the Netherlands, Poland, Spain, Sweden, the UK, and other CERN member states.

    If the Higgs boson discovery does not represent the pinnacle of international scientific cooperation, it surely sets a high standard. It will be a difficult one to match in the coming decades, given the conflicts and cleavages that have been erupting since Russia’s brutal Ukraine invasion. Russian scientific institutes have been at least temporarily excluded from future CERN projects—and the ban may well become permanent. And the costs of European rearmament could easily impact the CERN budget in the coming years. The first two decades of the 21st century will certainly represent a special moment in history when so many nations could work together peacefully in a common scientific pursuit of the greatest significance.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Our mission

    The mission of ”Physics Today” is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     

  • richardmitnick 8:13 am on July 2, 2022 Permalink | Reply
    Tags: "The Era of Higgs Physics", , , CERN LHC, , Higgs physics, , , , The DOE's Fermi National Accelerator Laboratory Tevatron Accelerator   

    From “Physics” : “The Era of Higgs Physics” 

    About Physics

    From “Physics”

    7.1.22
    Dan Garisto

    Ten years of Higgs physics have revealed how much more there is to learn about the mysterious particle.

    1
    At the Higgs discovery announcement, CERN Director General Rolf Heuer congratulates François Englert and Peter Higgs, who would later receive the 2013 Nobel Prize in Physics for their theoretical description of the origin of mass—which was confirmed by the Higgs boson detection.

    This article is part of a series of pieces that Physics Magazine is publishing to celebrate the 10th anniversary of the Higgs boson discovery. See also: Poem: Higgs Boson: The Visible Glyph; Research News: A Particle is Born: Making the Higgs Famous; (upcoming) Q&A: The Higgs Boson: A Theory, An Observation, A Tool; (upcoming) Podcast: The Higgs, Ten Years After; and Collection: The History of Observations of the Higgs Boson.

    On July 4, 2012, the discovery of a new particle was announced to a packed house at CERN in Switzerland. After presentations from the two main experimental collaborations of the Large Hadron Collider (LHC), then-CERN Director General Rolf Heuer took the stage. “As a layman, I would now say ‘I think we have it,’” he quipped. “You agree?” The audience—mostly physicists, including the particle’s namesake—cheered for the discovery of the Higgs boson.
    _______________________________________________
    Higgs


    _______________________________________________
    Since then, elation has mellowed, sobered by the sense that the Higgs boson is just another confirmation of the standard model, the theory of particles of matter—fermions—and their force-carrying counterparts—bosons.

    Despite its success, the standard model frustratingly lacks explanations for phenomena such as dark matter, gravity, and neutrino masses. If the Higgs boson had unexpected features, it might have given researchers a hint as to how to explain these missing pieces. As is, the Higgs’s failure to deviate from existing theory has left researchers adrift, without any clear route to theories beyond the standard model.

    Or so the story often goes. It is true that after ten years, nothing about the Higgs boson disagrees with the standard model predictions. But for the physicists who work on Higgs physics, this is a myopic view. Focusing on the lack of new physics ignores what has been learned about the Higgs boson over the past decade—and what more there is to learn.

    “Precision Higgs physics must be the toughest to publicize to the general public because you know, they will say, ‘well, if you already measured this, why does this matter?’” says Marcela Carena, a theoretical physicist at The DOE’s Fermi National Accelerator Laboratory in Illinois. “But in reality, it matters a lot.”

    [Earlier than the LHC at CERN, The DOE’s Fermi National Accelerator Laboratory had sought the Higgs with the Tevatron Accelerator.

    But the Tevatron could barely muster 2 TeV [Terraelecton volts], not enough energy to find the Higgs. CERN’s LHC is capable of 13 TeV.

    Another possible attempt in the U.S. would have been the Super Conducting Supercollider.

    Fermilab has gone on to become a world powerhouse in neutrino research with the LBNF/DUNE project which will send neutrinos 800 miles to SURF-The Sanford Underground Research Facility in in Lead, South Dakota.]

    For the last decade, scientists have worked to verify that the discovered Higgs is indeed the same Higgs boson that theorists predicted. Researchers at ATLAS and the Compact Muon Solenoid (CMS)—the LHC’s general-purpose experiments—continue to put the particle through increasingly rigorous tests, using novel techniques to uncover events—such as rare Higgs decays—that are hidden among similar-looking events or “backgrounds.”

    ___________________________________________________________________
    LHC

    LHC

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    ALICE

    CMS

    LHCb


    ___________________________________________________________________

    This ongoing effort offers a clear payoff, as it could answer outstanding questions related to how the Higgs couples to other particles and whether it is but one of many Higgs-like particles. Determining these Higgs properties, Carena points out, could also address underlying mysteries, such as the nature of dark matter or the origin of matter-antimatter asymmetry.

    Far from being a theoretical dead-end, the Higgs is more important than ever. “The Higgs boson is a unique particle that raises profound questions about the fundamental laws of nature,” the authors of the 2020 European Strategy Update wrote. “It also provides a powerful experimental tool to study these questions.”

    The Devil in the Details

    With hindsight, the discovery of the Higgs boson can appear foreordained, as though it was only a matter of time until the correct theory was confirmed. But in the years leading up to 2012, the Higgs discovery was far from certain.

    The standard model predicts that elementary particles acquire their mass through the Higgs boson. But right up to the discovery, theorists were still writing papers [Journal of High Energy Physics] about mass-generating mechanisms that did not involve the Higgs. These models were not as popular among theorists but still carried weight so long as the Higgs remained undiscovered.

    At the same time, experimentalists were having their own doubts. In 2011, ATLAS began seeing a signal indicative of a Higgs—but only in W-boson decays, which could not provide a precise Higgs mass. “People were really so anxious about the new data,” says Marumi Kado, the ATLAS Collaboration deputy spokesperson. “There was not a feeling of inevitability.”

    At the same time, experimentalists were having their own doubts. In 2011, ATLAS began seeing a signal [Proceedings of Science] indicative of a Higgs—but only in W-boson decays, which could not provide a precise Higgs mass. “People were really so anxious about the new data,” says Marumi Kado, the ATLAS Collaboration deputy spokesperson. “There was not a feeling of inevitability.”

    By early 2012, hints of a possible Higgs boson with a mass of around 125 GeV were around the three σ benchmark, a measure of statistical significance that is lower than the five σ level conventionally used to claim a discovery. “I think at that point, it was clear that we were likely going to hit a discovery with the additional data that we were going to collect,” says Nicholas Wardle, an experimentalist and coleader of Higgs physics for the CMS Collaboration.

    The discovery came in July, but LHC researchers initially referred to the detected particle as a “Higgs boson candidate,” as major uncertainties remained even after the announcement. Some of the early data suggested, for example, that the new particle was decaying into two photons [Physical Review Letters] at double the rate predicted by the standard model. The excess fueled speculation [Physical Review D] that the detected particle might have spin 2, not the predicted spin 0. “There were a lot of bolts that needed to be tightened,” Kado says. “It was nerve-racking.”

    With the full Run 1 dataset available by 2013, researchers were able to put some worries to bed. The newly discovered Higgs is indeed a spin-0 particle, and it is CP-even—meaning that it couples to particles in the same way that it couples to antiparticles with reversed parity. Additionally, measurements from ATLAS and CMS managed to pin down the Higgs mass to 125 GeV, with an error of less than 1%.

    Getting to Know the Higgs

    Run 2, which went from 2012 to 2015, allowed ATLAS and CMS to increase their data sixfold. “We just had so much more data,” Wardle says. “That opens up a whole new realm of possibilities.” New machine-learning approaches were able to sift through noisy backgrounds, clearly identifying particles like bottom quarks, even amid the wreckage of a messy collision.

    On the theory side, researchers went to extreme lengths to reduce uncertainties, using so-called next-to-next-to-leading order calculations for processes such as top quark production [Physical Review Letters]. By considering additional, smaller terms in the infinite series that represents the interaction between two particles, they were able to make unprecedentedly precise predictions. Improvements to the detectors also enabled better event discrimination.

    Representative of this progress are measurements of the Higgs decay to two muons. The signal for this rare event is normally lost in the noise of Z-boson decays to two muons. Despite the difficulty of the search, the ATLAS [Physics Letters B] and CMS [Journal of High Energy Physics] collaborations recently reported three σ evidence for the Higgs decaying to two muons—providing hope that researchers will soon claim discovery of this seemingly out-of-reach detection.

    The decay to muons is unique in that it would be the first evidence of the Higgs interacting with a lighter fermion—previous observations of Higgs-fermion interactions have all involved the heaviest fermion generation (bottom quark, top quark, and tau lepton). Discovering that all mass-bearing particles get their heft from the Higgs would be a critical confirmation of the standard model and would help rule out competing theories with multiple Higgs particles.

    2
    Higgs boson decaying into two muons (red tracks) in the ATLAS detector. ATLAS Collaboration/CERN

    Because the Higgs was expected to couple with muons, this development has been met with muted enthusiasm. In fact, many physicists are finding the Higgs to be a bit too “standard” for their tastes, with no signs of new physics that might expose cracks in the standard model. Excitement temporarily rose in 2015 when strange data [Physical Review Letters] appeared at energies of 750 GeV, but the anomaly was later found to be a statistical fluke.

    Other results, such as the discovery of the Higgs coupling to the top quark, have met similarly subdued reactions. “We didn’t make a sufficient amount of fuss,” laments Kado. He says that people assume that a result that matches the standard model must be obvious, when in fact much about the Higgs has yet to be established by experiment.

    Standard Remodeling

    Standard model or not, the Higgs itself revolutionized the field. “There was a blossoming of new ideas, and the landscape of particle physics completely changed,” says Kado. Carena agrees: “After you discover the Higgs, the first question you have is, ‘Well, why not more of that kind?’” Many theorists have wondered about models with multiple Higgs particles, possibly hiding at higher energies, or even entire sectors connected to the Higgs.

    Models with Higgs portals [Physics Reports]—connections to a coterie of extremely feebly interacting particles coupling only to the Higgs—have flourished because of their ability to explain dark matter and other outstanding issues with the standard model. Supersymmetric (SUSY) theories—which propose a new symmetry between bosons and fermions—still have a place in the theorist’s toolbox, but because of a lack of evidence, they are no longer predominant. Instead, theorists work more closely with experimental results. “There are a lot of inputs we have gotten from experimental data that have constrained the way we build models,” Carena says.

    New ideas from theorists have also shaped the experimental program. This fruitful interplay is perhaps best encapsulated by the effective field theory (EFT) [Pramana] approach at the LHC. Using the EFT approach, theorists can guide experimentalists to make precision measurements sensitive to undiscovered particles. For example, the decay of a Higgs to a Z boson and a photon is mediated by contributions from all particles. If the decay rate deviates from predictions, that could be a sign of an unseen heavy particle.

    Even if a Higgs decay matches standard model predictions, it can still provide valuable information. Some alternative Higgs models, Wardle points out, predict that the Higgs boson couples to leptons, such as the electron, differently than to quarks. As such, determining all the coupling strengths and other Higgs parameters isn’t stamp collecting—as some derisively call such measurements—but a vital effort to put limits on theories, he says.

    Run 3 will begin in earnest on July 5, 2022, the day after the 10th anniversary of the Higgs discovery, promising particle physicists a new tranche of data to pore over. Wardle hopes data will allow CMS to reach five sigma and declare a discovery for the Higgs decay to two muons. LHCb (one of the more-specialized LHC experiments) could play a role as well by probing the Higgs coupling to charm quarks. The search for beyond-the-standard-model Higgs properties is “now one of the main pillars of the CMS search program,” says Jan Steggemann, a coleader of Higgs physics for the CMS Collaboration. Carena is particularly interested in the Higgs’ self-coupling, which the High Luminosity LHC—an upgrade planned for 2029—will be able to measure via two-Higgs production.

    Accelerating Improvements

    In 1975, the first paper on Higgs boson “phenomenology”—data-driven predictions—concluded with regrets from the authors: “We apologize to experimentalists for having no idea what is the mass of the Higgs boson.” They were also sorry for being unsure about its couplings to other particles. “For these reasons, we do not want to encourage big experimental searches for the Higgs boson.” Four decades later, physicists have not only found the Higgs, but they have assembled a collection of millions of detections of these elusive particles using the LHC as the world’s first “Higgs factory” (see Opinion: Exploring Futures for Particle Physics).

    3
    The Higgs boson is often referred to as the missing piece to the standard model, which explains how the known fundamental particles fit together. Johan Jarnestad/The Royal Swedish Academy of Sciences.

    What was once too inaccessible to dream of has become standard, in part because physicists have surpassed their own projections. “There were people who claimed that the LHC was too ‘dirty’ a machine,” Steggemann says, referring to large backgrounds that can obscure small signals. But he says that physicists have developed techniques, such as machine learning, that can filter through the dirt. And those efforts are paying off, as once-thought-impossible measurements, like the Higgs decay to two muons, are now eminently possible.

    Ten years after its discovery, the Higgs may have disappointed some with its adherence to the standard model. But its apparent conformity has proven useful, and its remaining secrets continue to inspire particle physicists. “I don’t think particle physics is in a crisis—we have so many things to explain,” Carena says. “I would call it an opportunity.”

    See the full article here .

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    Stem Education Coalition

    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries. Physics provides a much-needed guide to the best in physics, and we welcome your comments.

     

  • richardmitnick 9:01 pm on July 1, 2022 Permalink | Reply
    Tags: "A Particle is Born:: Making the Higgs Famous", "Particle Fever", , , CERN LHC, , Leon Lederman of Fermilab "The God Particle", , , , Sean Carroll "The Particle at the End of the Universe", The DOE's Fermilab National Acccelerator Laboratory Tevatron Particle Accelerator   

    From “Physics” : “A Particle is Born:: Making the Higgs Famous” 

    About Physics

    From “Physics”

    June 30, 2022
    Michael Schirber

    Science communicators had a field day with the 2012 Higgs discovery, as it offered a chance to energize the public about fundamental physics research.

    1
    Figure 1. A representation of the standard model, designed by Walter Murch for the 2013 film Particle Fever. The Higgs boson is shown in the center, surrounded by the other particles—the photon and other “force-carriers” in blue, the electron and other “leptons” in green, and the quarks in red.

    This article is part of a series of pieces that Physics Magazine is publishing to celebrate the 10th anniversary of the Higgs boson discovery. See also (upcoming): Poem: Higgs Boson: The Visible Glyph; News Feature: The Era of Higgs Physics; Q&A: The Higgs Boson: A Theory, An Observation, A Tool; Podcast: The Higgs-Ten Years After; and Collection: The History of Observations of the Higgs Boson.

    The Higgs discovery, announced on July 4, 2012, was a major happening in science but also in science communication.
    _______________________________________________
    Higgs


    _______________________________________________

    [Earlier than the LHC at CERN, The DOE’s Fermi National Accelerator lab had sought the Higgs with the Tevatron Accelerator.

    But the Tevatron could barely muster 2 TeV [Terraelecton volts], not enough energy to find the Higgs. CERN’s LHC is capable of 13 TeV.

    Another possible attempt in the U.S. would have been the Super Conducting Supercollider.

    Fermilab has gone on to become a world powerhouse in neutrino research with the LBNF/DUNE project which will send neutrinos 800 miles to SURF-The Sanford Underground Research Facility in in Lead, South Dakota.]
    ___________________________________________________________________

    Rarely has so much effort been made to engage the public over a fundamental physics topic. Front-page headlines, best-selling books, public lectures, TV interviews, and feature-length films all tried to explain the Higgs boson—a particle whose claim to fame is its association with the generation of mass. Ten years later, the Higgs may not be a household name, but the intense limelight on this fundamental entity did offer communicators an opportunity to tell a larger story about the scientific enterprise.

    “The Higgs boson is the capstone of the standard model of particle physics,” says physicist Sean Carroll from the California Institute of Technology, who wrote about the Higgs in his 2012 book The Particle at the End of the Universe. He’s also helped to popularize the Higgs by giving public lectures, writing blogs, and making TV appearances. He believes the discovery was a “watershed moment,” as it showed that physicists were clearly on the right track with their understanding of the fundamental workings of the Universe. “That kind of accomplishment should not go unrecognized,” Carroll says.

    So how have science communicators tried to make the Higgs boson famous? One of the earliest attempts was by the Nobel prize winner Leon Lederman, who wrote the 1993 popular science book The God Particle. In it, Lederman described the Higgs as the crucial but elusive piece to our understanding of the structure of matter. “[The book] was spectacularly successful in that you literally cannot have a conversation with a person on the street about the Higgs without someone talking about the God particle,” Carroll says. But many physicists regret the connection that was made between the Higgs and religion. “There’s a lot of work to be done in undoing the damage,” Carroll says.

    Another early attempt at capturing the public’s imagination came with the cocktail party analogy, which earned David Miller of the University College London a bottle of champagne from the UK science minister in 1993. Miller likened the Higgs field—a space-filling energy out of which the Higgs boson arises—to a bustling crowd of partygoers. When a celebrity tries to walk through the room, the crowd presses toward them, slowing their progress. In a similar way, the Higgs field can be drawn toward a particle, slowing its progress and giving it mass. The Higgs is more drawn, for example, to the top quark than to the up quark, hence the top is more massive than the up.

    These types of metaphors offer a basic appreciation of the physics behind the Higgs boson and its field. But getting people to take the time to learn about the Higgs requires a more human approach, says Mark Levinson—director of the 2013 film Particle Fever. “If you really want to get the message out, if you want to engage a bigger audience, it needs to be personalized,” he says. His award-winning film—which ran in theaters across the globe and was distributed on Netflix—recounts the efforts at CERN in Geneva leading up to the Higgs discovery, with Levinson’s cameras following a handful of theorists and experimentalists during their day-to-day activities. “It is interesting to show why people pursue these incredibly abstract ideas,” he says.

    When Levinson started shooting in 2008, he was not focused on the Higgs boson, as physicists had warned him that a discovery might take too long to materialize. But once promising signs showed up at CERN’s Large Hadron Collider (LHC), Levinson and his editor Walter Murch retooled their film’s narrative to give a leading role to the Higgs. They even created a graphic with the Higgs in the center—a representation that the physics community has come to embrace, Levinson says (Fig. 1). The movie’s big climactic scene is when LHC scientists revealed their data to a packed auditorium that included a visibly moved Peter Higgs, who began working in the 1960s—along with other theorists—on his namesake particle. Seeing an 80-year-old physicist tear up over a vindication of his life’s work, “that’s a great story,” Levinson says.

    The 2012 announcement was a media hit as well, with over 12,000 news reports on the Higgs boson, according to James Gillies, who was head of CERN’s communication group when the discovery was announced (Fig. 2). Like Levinson, Gillies believes the Higgs was an easy sell to the public because the human effort surrounding the discovery was so immense. “We cast fundamental science as the latest step in humankind’s journey of exploration,” he says.

    2
    Figure 2. The Higgs discovery was covered by newspapers from around the world.

    Gillies admits that it can be difficult to assess whether the Higgs excitement had a lasting impact on the public’s appreciation of fundamental science. Very little data has been collected on changes in scientific understanding following a big discovery. “But there’s no doubt in my mind that CERN, LHC, and Higgs are quite common currency these days,” Gillies says. “My experience has taught me that people are more curious about basic research than we tend to think.”

    Levinson agrees. “Many people have said, I really didn’t understand it, but I loved the film.” The science, he says, is rather complicated, but the story about scientists and their passion is something that audiences can identify with. “The Higgs is fundamental to the physics theory, but it’s bigger than that,” Levinson says. “It’s more about our quest to understand the way the Universe works.”

    “There’s no shortage of enthusiasm among the public to learn about the Higgs boson,” Carroll says. He thinks science communicators can always do better, “but I think the Higgs boson is something where we did take advantage of the excitement to teach people a little bit of physics.” For his part, Carroll used the discovery to explain some of the quantum field theory that lies at the basis of the Higgs boson prediction. “We might as well leverage our big, happy discoveries to better acquaint the public with how science works and what scientists are finding.”

    ___________________________________________________________________
    LHC

    LHC

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    ALICE

    CMS

    LHCb


    ___________________________________________________________________

    See the full article here.

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    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries. Physics provides a much-needed guide to the best in physics, and we welcome your comments.

     

  • richardmitnick 1:01 pm on June 30, 2022 Permalink | Reply
    Tags: "Four things physicists still wonder about the Higgs boson", 1. Does the Higgs boson interact with itself?, 2. How does the Higgs couple to other particles?, 3. Are there other Higgs particles?, 4. Is the Higgs connected to dark matter or other unusual particles?, , Alternative theories that extend the Standard Model call for many more types of Higgs particles., , By measuring the Higgs very precisely we can gain an understanding of physics beyond the Standard Model and maybe find a portal to a new sector that is beyond the Standard Model., CERN LHC, , How will physicists answer these questions?, If there are other Higgs particles out there physicists hope to see their footprints in collider experiments., It took 60 years to first detect the Higgs boson and in the past 10 years we've gotten to know it quite well., , , , , When the news of Higgs came on July 4 2012 it moved some scientists to tears., Yet there’s still a lot to learn.   

    From “Symmetry”: “Four things physicists still wonder about the Higgs boson” 

    Symmetry Mag

    From “Symmetry”

    06/30/22
    Mara Johnson-Groh

    1
    Illustration by Sandbox Studio, Chicago with Corinne Mucha.

    Scientists have learned a lot about the Higgs boson in the decade since they discovered it. But intriguing questions remain.

    Higgs

    When the news of Higgs came on July 4 2012 it moved some scientists to tears. Others jumped and cheered. After decades of anticipation, physicists had at last discovered the Higgs boson.

    In the years since that initial detection, physicists have become more and more familiar with this fundamental, force-carrying particle that is produced by the invisible field that gives particles mass. They’ve improved measurements of the Higgs boson’s mass, width, spin, couplings to different particles and other characteristics. They’ve gotten more precise measurements than they expected to be able to make.

    Yet there’s still a lot to learn. Most measurements of the Higgs haven’t yet reached the precision scientists need to differentiate between models that could lead to new insights and discoveries. Some aspects of the Higgs boson haven’t even been probed yet.

    “It took 60 years to first detect the Higgs boson and in the past 10 years we’ve gotten to know it quite well,” says Rebeca Gonzalez Suarez, a CERN physicist, the education and outreach coordinator for the ATLAS Collaboration and an associate professor at Uppsala University in Sweden. “So far it looks very normal—very much like the expectations we have of it from the Standard Model. But there’s still possibilities for it to surprise us.”

    Today, physicists are continuing to refine their measurements—and even develop ideas for future colliders—in order to fully unveil the mysteries of the Higgs boson and its place in the universe.

    “By measuring the Higgs very precisely we can gain an understanding of physics beyond the Standard Model and maybe find a portal to a new sector that is beyond the Standard Model,” says Kétévi Assamagan, a physicist at the US Department of Energy’s Brookhaven National Laboratory in New York.

    As physicists try to reach a more and more precise understanding of the Higgs, here are four questions they’re hoping to answer.

    2
    Illustration by Sandbox Studio, Chicago with Corinne Mucha.

    1. Does the Higgs boson interact with itself?

    One of the biggest questions about the Higgs is how it might interact, or couple, with itself.

    “I think this is the main question about the Higgs right now,” says Caterina Vernieri, assistant professor and a Panofsky Fellow at SLAC National Accelerator Laboratory. “It’s really an unknown cornerstone in our understanding of the Higgs.”

    Experiments have shown the Higgs couples with other particles [providing mass], including a menagerie of fundamental particles like the W and Z bosons, quarks, taus and muons. According to the Standard Model, it’s also expected to couple with itself.

    Uncovering the exact details of how this happens could help physicists further refine the Standard Model, and even shed light on the evolution of the early universe and the matter and antimatter imbalance.

    If physicists learn that the Higgs boson does not interact with itself in the manner predicted by the Standard Model, it could upend their understanding of the particle and suggest that the universe isn’t in the energy state that physicists predict, which could affect the rules of how matter interacts.

    To find out if the Higgs self-couples, physicists are looking at particle collisions for hints of Higgs boson pairs, or even rarer Higgs boson triplets, which would only be created if the Higgs self-couples.

    Thus far, data from experiments at CERN’s Large Hadron Collider haven’t yet seen a pair of Higgs bosons, but they also haven’t ruled out the possibility—there just simply isn’t enough data yet.

    According to predictions from the Standard Model, the self-coupling should produce pairs of Higgs bosons infrequently at collider experiments—over 1,000 times less often than a single Higgs boson is produced.

    Physicists are hoping that future runs will be able to help narrow this down as the LHC turns out more Higgs boson-producing events.

    3
    Illustration by Sandbox Studio, Chicago with Corinne Mucha.

    2. How does the Higgs couple to other particles?

    While physicists don’t yet know if the Higgs couples to itself, they do know it couples to other particles. In some cases—as with the top quark, the heaviest of the Standard Model particles—the coupling is quite well understood. But physicists are just starting to get a handle on how much other particles, like the comparatively lighter muon, interact with Higgs bosons.

    How much a given particle will couple with a Higgs is predicted by the Standard Model and is related to the particle’s mass: The more massive the particle, the greater the coupling. So far, measurements of couplings match these predictions. But the precision of these measurements isn’t yet great enough to see if there could be any deviations from the Standard Model. Knowing exactly how the Higgs couples can help scientists understand how particles get their mass.

    “If we see any discrepancies when we take precision measurements of the Higgs boson coupling with other particles, that can tell us if there is new physics out there,” Vernieri says.

    3
    Illustration by Sandbox Studio, Chicago with Corinne Mucha.

    3. Are there other Higgs particles?

    So far, physicists have found only one Higgs boson, which is what the Standard Model predicts. But some alternative theories that extend the Standard Model call for many more types of Higgs particles.

    “There is no reason why there shouldn’t be more,” says Sally Dawson, a theoretical particle physicist at Brookhaven National Laboratory.

    “There’s a whole host of possibilities on what that could look like.”

    Some models suggest there’s a version of the Higgs that has different properties from the boson we know. The Higgs boson discovered in 2012 has zero spin and no electric charge, but other Higgs particles could have different characteristics. Other models propose there’s one type of Higgs that interacts with heavy particles and another that interacts with lighter particles. Or maybe the Higgs particle we see is really a composite of multiple different particles.

    “Any additional Higgs that we may discover would indicate that there must be new physics,” Assamagan says. “It could help us explain some of the things that don’t necessarily fit in the Standard Model.”

    Some phenomena that could be explained by additional Higgs particles include dark matter, neutrino oscillations, the mystery of neutrino masses, and why there’s an imbalance of matter and antimatter in the universe.

    If there are other Higgs particles out there physicists hope to see their footprints in collider experiments.

    4
    Illustration by Sandbox Studio, Chicago with Corinne Mucha.

    4. Is the Higgs connected to dark matter or other unusual particles?

    Because the Higgs boson helps explain where mass comes from, many scientists think it should interact with dark matter: the mysterious substance that seems to be connected with everyday matter only through gravity.

    “The Higgs could be the portal between us and this dark sector that could hide dark matter,” Gonzalez Suarez says.

    Certain theories predict that dark matter interacts with normal matter by swapping Higgs bosons. If this is the case, then a collision that produces Higgs particles could also create dark matter particles.

    “The Higgs in the Standard Model doesn’t decay into dark matter, but some models suggest there’s an interaction,” Dawson says. “It’s very possible that measuring Higgs properties could tell you something about dark matter.”

    In other scenarios, when the Higgs decays, it could produce other completely new, invisible particles that physicists haven’t even considered. No unusual particles have been seen in collider experiments—where their existence would be inferred from missing energy in the aftermath of a collision—but physicists aren’t done looking.

    How will physicists answer these questions?

    Physicists are studying the Higgs at the LHC, which is just ramping up again after a three-year hiatus following upgrades to the experiments and accelerator complex and pandemic delays. These upgrades are intended to allow physicists to make more precise measurements of the Higgs boson. However, unless there are very big discrepancies, this precision is probably not enough to see if there are any deviations from the Standard Model.

    After the current run, which is scheduled to last until the end of 2025, the LHC will receive another upgrade that will transform the accelerator into the next-generation High-Luminosity LHC, which is scheduled to run until about 2040. This will allow physicists to measure how the Higgs couples to other particles down to around 5% uncertainty. While physicists expect to produce more Higgs bosons during this high-luminosity phase, measuring self-coupling will still be a challenge.

    In the long term, scientists are thinking about ways to study Higgs bosons beyond the LHC, which was designed to study a large range of phenomena via proton-proton collisions. Protons collide in a wide variety of ways, giving scientists a lot of ground to cover when they’re not sure where to look. But they’re messy, which can make it hard to pinpoint specific types of particles and events.

    That’s why some scientists have proposed a future “Higgs factory,” which they could tune specifically to produce many Higgs bosons. Instead of colliding protons, a Higgs factory would collide matter and antimatter pairs, such as electrons and positrons. These particles would annihilate one another, eliminating much of the messiness of the collisions observed at the LHC and allowing scientists to take a closer look at the Higgs bosons produced. Such an instrument should enable scientists to reach 1% accuracy for precision measurements of most couplings and probe theoretical predictions for Higgs self-coupling.

    In the meanwhile, physicists aren’t out of hope that something unexpected will show up in ongoing experiments. With each upgrade to the LHC, there’s a chance physicists could see new particles or connections to new, hidden sectors. Or perhaps unexpected factors could allow, for example, pairs of Higgs to be produced in larger quantities than anticipated, Gonzalez Suarez says.

    “You never know with experimental science,” Dawson says. “It’s always exciting because there are so many possibilities, and we don’t know which one is right.”

    See the full article here .


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  • richardmitnick 10:03 am on June 23, 2022 Permalink | Reply
    Tags: " 'Particle Fever':: Where are they now?", , , CERN LHC, David Kaplan, , Monica Dunford, Nima Arkani-Hamed, , , ,   

    From “Symmetry”: ” ‘Particle Fever’:: Where are they now?” 

    Symmetry Mag

    From “Symmetry”

    06/23/22
    Sarah Charley

    The 2013 documentary Particle Fever follows physicists from the start-up of the LHC through the discovery of the Higgs boson. Where are those physicists now?

    1

    Physicist Monica Dunford remembers when the CERN press office asked her if she wanted to be interviewed by a visiting documentary film crew. It was 2007, and she had just arrived at CERN as a postdoc on the ATLAS experiment.

    “I thought I would do this interview and that would be that,” she says. “I didn’t know it would be 100 hours of filming.”

    Six years later, Dunford watched herself on the big screen as the feature-length documentary Particle Fever premiered at Sheffield International Documentary Festival, one of the largest and most influential documentary film festivals in the world.

    “People would recognize me,” she says. “I remember thinking, I never want to be famous. I just want to have my breakfast, and nobody knows who I am.”

    The 2013 documentary Particle Fever follows a handful of experimental and theoretical physicists during the lead-up to the discovery of the Higgs boson, the last predicted piece of the Standard Model of particle physics.

    It captures the excitement of the Large Hadron Collider starting up, the despair when a faulty weld destroyed several magnets, and the utter joy when scientists finally announced the discovery of the Higgs.

    It’s a human-centered story. “We constructed the story with as little physics as possible,” says producer David Kaplan, a theoretical physicist who also appears in the film. “Once the story was there, we put in just enough physics to explain the emotional content of the film.”

    Over the last 10 years, the LHC research program has moved beyond the search for the Higgs, and so have the physicist featured in Particle Fever. Today, Symmetry checks in with experimentalist Monica Dunford and theorists David Kaplan and Nima Arkani-Hamed to see how their lives, work and perspectives have evolved since filming wrapped in 2012.

    Monica Dunford

    Professor, Heidelberg University
    Experimental physicist, ATLAS experiment

    When Particle Fever was filmed, Dunford had just gotten her PhD and was working as a postdoc on the ATLAS experiment with the University of Chicago. Physics and her physics community were everything.

    “We would blur from the control room to a bar somewhere and then to a hiking trip, like a massive family,” she says. “I look back at that time, and it feels like my 20s. It was very intense. But it wasn’t sustainable.”

    Today, Dunford is a physics professor at Heidelberg University. She sees that same electricity in her students. But her priorities have changed.

    “I’m not in my 20s—and don’t want to be in my 20s—anymore,” she says. “I like my expensive wines.”

    Her focus has shifted from hands-on analysis work to leadership. In October Dunford will take on the role of ATLAS Physics Coordinator, which means overseeing the physics output from ATLAS’s 3,000 scientific authors. As a professor, Dunford mentors students and postdocs as they explore big questions, such as links between particle physics and cosmology. Becoming a professor also means new responsibilities, such as grant-writing, administrative duties, and teaching. Instead of excitedly showing colleagues her plots in the ATLAS Control Room (as she does in Particle Fever) Dunford is focused on cultivating the next generation of physicists.

    “I am a strong believer that the world rides on its youth,” she says.

    Dunford’s personal life has also evolved. In Particle Fever, Dunford is filmed biking, running and rowing. While she’s still very active (and hopes to complete an Ironman one day), she now has a family with two small kids.

    “Back in Geneva, we would do 20-mile hikes and up god knows how many meter mountains,” she says. “With kids, it takes us about six hours to do 3 kilometers. There are stones to pick up, and then rivers to throw stones into. It’s a different pace.”

    As Dunford has matured, so has her perspective on physics. In Particle Fever, Dunford says on camera that finding the Higgs boson—and only the Higgs boson—would be the worst-case scenario for the LHC. She was confident that the LHC would find many new particles, as predicted by the popular theory of supersymmetry, which would resolve many questions in fundamental physics. A decade (and no supersymmetric particles) later, her perspective is more nuanced.

    “The world is more complicated, and that’s OK,” she says. “I’ve come to see that it’s more interesting this way.”

    David Kaplan

    Professor, Johns Hopkins University
    Theoretical physicist

    Theoretical physicist David Kaplan wasn’t just a subject of the documentary Particle Fever—he was also the originator of the film.

    “In 2006 I decided to make this movie, and I was going to do it all by myself,” he says.

    After talking with his sister in Los Angeles, he quickly scrapped the solo plan. For the next seven years, Kaplan worked with an evolving team of filmmakers, including director Mark Levinson and Academy Award-winning editor Walter Murch. In 2013, their documentary premiered at the Sheffield DocFest. Kaplan remembers feeling both excited and nervous.

    “It was unnerving to watch myself,” Kaplan says. “The showing was jam-packed with a line out the door. It was the first time I was seeing the completed film.”

    Particle Fever was a huge success, going on to win awards at film festivals around the world. Kaplan says he still gets recognized today. “People will still come up to me at conferences to say that they saw Particle Fever in high school and it inspired them to do physics,” he says.

    When Kaplan started making Particle Fever, he was an assistant professor at Johns Hopkins University with two little kids. Today, his kids are in their 20s and his family has grown to include two stepchildren as well (now also in their 20s). Kaplan is still a professor at Johns Hopkins University, the only difference is that he now has tenure.

    “I’m still just a normal professor,” Kaplan says. “Nothing changed that way. But my attitude toward research has changed.”

    Before Particle Fever, Kaplan says he primarily looked for research projects that he could wrap up over a six-month period. “Our field has this addiction to citations, which forces you to think short-term,” he says. “You take a quick idea and turn it around into a quick paper.”

    Particle Fever was the first time Kaplan was able to take a big, exciting, and somewhat nebulous idea and run with it to completion.

    “Particle Fever was a huge success, and it took seven years,” he says. “Now, if I see something really important and worthwhile, then I’m going to go after it, even if it will take years.”

    He’s shifted his focus from model-building to pondering big structural problems in physics with his postdocs and students. “I’m not just looking for something different but thinking about our approach—what our real goal is,” he says. “It’s possible to solve harder problems if you spend more of your time on it.”

    Nima Arkani-Hamed

    Professor, Institute for Advanced Study in Princeton
    Theoretical physicist

    In Particle Fever, theorist Nima Arkani-Hamed says on camera, “I’ve spent the last 15 years thinking about the LHC.”

    Today, he’s still thinking about collider physics, but from different points of view. “I still think about the same questions,” he says. “The questions are really big and take a long time to solve.”

    One of these questions is the extent to which nature is governed by elegant principles, and the extent to which everything is the result of random (and happy) accidents. Particle Fever explores this dilemma during a scene in which Arkani-Hamed and Kaplan play ping-pong in a game of “multiverse versus supersymmetry.”

    Arkani-Hamed represents the idea that our universe is just one of infinite universes, all with their own rules of physics. Kaplan represents supersymmetry, a theory that neatly tidies up much of the messiness of the Standard Model of physics. But at the time of filming, Arkani-Hamed was actually toying with a conglomerate of both.

    “Before the LHC turned on, I wrote a paper with Savas Dimopoulos—another theorist in the movie—about a version of SUSY inspired by the multiverse,” he says. “It was really radical and it took us a long time to get those two words in the same sentence. It was very unpopular at first. It was the only time in my life that I’ve been yelled at during a conference. But this theory ended up being studied actively.”

    This so-called split-SUSY embraces the elegance of supersymmetry while simultaneously leaning into the chaos of the multiverse. Unlike more conventional forms for supersymmetry, it hasn’t been ruled out by the LHC (and was actually bolstered by measurements of the Higgs mass, according to Arkani-Hamed).

    Arkani-Hamed still feels split-SUSY could be an underlying feature of nature. While he waits for experimental results, he’s exploring new frontiers.

    After the LHC turned on, Arkani-Hamed spent three years developing and communicating the theoretical motivation for a next-generation supercollider. His primary focus was the proposed Circular Electron Positron Collider in China.

    “I was flying back and forth a lot between Newark and Beijing,” he says. “You get on the flight, you get your Coke from the flight attendant, you watch all three Lord of the Rings movies back-to-back, and then you only have another four hours to go.”

    Now that the physics case is made, he has taken a step back as international organizations and government agencies take the next steps forward. “I’m not good at politics,” Arkani-Hamed says.

    Over the past decade, Arkani-Hamed’s theoretical research has shifted to investigating physics at the most basic level: the interactions of subatomic particles. Arkani-Hamed and his collaborators are hoping to find a new mathematical understanding of particle interactions that will help scientists reverse-engineer the properties of two things that are even more fundamental: spacetime and quantum mechanics.

    “At the deepest level, everything is governed by spacetime and quantum mechanics,” he says. “Thinking about the origins of spacetime and quantum mechanics has always been part of my grand plan, ever since I was an undergraduate.”

    See the full article here .


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  • richardmitnick 10:10 am on June 21, 2022 Permalink | Reply
    Tags: Abhishek Panchal-India, , , Caleb Fangmeier-USA, CERN LHC, Federico Ronchetti-Italy, , Jurina Nakajima-Japan, , , , , The Higgs boson   

    From “Symmetry”: “Reverberations of the Higgs” 

    Symmetry Mag

    From “Symmetry”

    06/21/22
    Nikita Amir

    1
    Illustration by Sandbox Studio, Chicago with Corinne Mucha.

    The discovery of the Higgs boson inspired young people around the world to pursue a career in science and technology.

    The Higgs boson is the final predicted piece of the Standard Model, physicists’ best understanding of the elementary particles and forces that underlie our existence.

    But finding the Higgs particle proved to be a difficult task.

    On July 4, 2012—almost 50 years after theorists first predicted the existence of the Higgs boson—scientists representing the CMS and ATLAS experiments at the Large Hadron Collider made one of the biggest scientific announcements in recent memory. They had discovered the Higgs at last.

    The news quickly traveled across the planet. Meet four people whose academic and career trajectories were affected by the momentous discovery.

    1
    Abhishek Panchal, India

    Abhishek Panchal can trace his love for physics back to his days at a boarding school in the Surat district of Gujarat, India. At age 13, during his first year away from his family and friends, he sought refuge in books. In a series he found on famous historical scientists, Panchal first encountered the term “elementary particles.” He fondly remembers flipping back the purple cover of his big Collins Dictionary of Science to look for more information about quarks, protons, hadrons and leptons.

    “Science was just something very logical. It was something other than magic, that was like magic for me,” he says. “At the time, I had this dream that when I became a scientist and discovered a new particle, I’d name it Abhion, for my name—yeah, it was very silly.”

    A year later, scientists at the Large Hadron Collider at CERN announced the discovery of the Higgs boson. As the news became a talking point among the students around him, Panchal found he had something to contribute to the conversation; he actually knew a thing or two about the particle physics world. “Even people who weren’t into science, they wanted to know about it,” he says. “I think that really helped a lot of people, not just me, to get into science in this field.”

    After graduation, Panchal began a bachelor’s degree in physics at the Centre for Excellence in Basic Sciences in Mumbai and quickly jumped into a summer research project with the only particle physicist he knew in the department. He stuck with particle physics until the final year of his degree program, when he took a class in quantum electrodynamics and decided to change course.

    Today Panchal is a master’s student in laser plasma physics at the Institut Polytechnique de Paris. His research involves working on a new technique for accelerating electrons. He hopes to apply his research in the emerging field of electron therapy to treat cancer.

    “It’s not related at all to whatever I started to do, but I think it’s evolved in a good way,” he says.

    2
    Caleb Fangmeier, USA

    Caleb Fangmeier grew up on a farm near Lincoln, Nebraska. He thought he had a future in engineering, until an administrative mix-up at the University of Nebraska-Lincoln set his major to physics.

    He went with it. And as he started taking classes, he grew more interested in the field.

    “One of the lightbulb moments for me was working with a graduate student,” he says. “We had made a couple of plots and I was looking at it like, This is real data that was collected at the LHC. I thought that was so cool and kind of took off from there.”

    Fangmeier was a student in the summer of 2012, when rumors swirled about the impending discovery of the Higgs boson. Fangmeier decided to stay up until 2 in the morning, Nebraska time, to tune in for the big announcement.

    “It was historic, right?” he says. “It’s one of those moments in the history of physics that only comes once in a while.”

    Fangmeier says he thinks that if nothing new had come out of the LHC, then his attention might have shifted to a different part of physics. Instead, the novelty and excitement helped Fangmeier stay dedicated to the field—though, ironically, his interests have shifted back over toward the engineering side.

    Today, Fangmeier runs a lab at his alma mater, where he designs detector parts for CMS, one of the two experiments scientists used to discover the Higgs.

    3
    Jurina Nakajima, Japan

    Jurina Nakajima was 16 when she first learned about particle physics. She went out and bought a copy of the Japanese science magazine Newton to learn more. That same year, news of the Higgs broke, the excitement spread around her peers and teachers as well.

    “I remember feeling even more fascinated that there was an undiscovered thing in the world and that we found it,” she says. “I thought, if I study elementary particles, I will also be able to find new particles that no one knows about.”

    That interest carried her through her studies all the way to her current PhD program. She is working on research related to the International Linear Collider, a proposed particle accelerator designed to be a “Higgs factory.” It would produce massive amounts of the particle that inspired Nakajima so that scientists can measure it to new levels of precision.

    These precision measurements could tell scientists about more than just the Higgs—including whether there are more undiscovered particles hiding out of our view.

    4
    Federico Ronchetti, Italy

    Federico Ronchetti heard the news about the discovery of the Higgs boson on top of a mountain near Como in Italy, while on a trip with a friend’s family. He was 16 years old.

    He didn’t fully understand the significance of the event at the time, but he started looking into it as soon as he got home. Ronchetti was amazed at how people from all over the world—from physicists to engineers to mechanics—came together to make the discovery possible.

    In high school, Ronchetti had the chance to visit CERN, the site of the Higgs discovery. He and his classmates ventured underground on a tour of the towering ALICE detector, a sight that helped solidify his love for physics.

    Ronchetti enrolled at the University of Insubria, where he developed an interest in medical physics. As a student, he returned to CERN, this time for a month with his research group to perform tests on silicon detectors.

    Actually working on detector technology at the home of the LHC steered Ronchetti back toward particle physics. “As someone interested in detector research and development, being at CERN is the best possible thing one can do,” he says.

    He completed his master’s degree and is now applying to PhD programs. For inspiration, he keeps a poster on his wall of the moment the Royal Swedish Academy of Sciences awarded the Nobel Prize to theorists François Englert and Peter W. Higgs.

    See the full article here .


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    Please help promote STEM in your local schools.


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    Symmetry is a joint Fermilab/SLAC publication.


     

  • richardmitnick 9:21 am on June 18, 2022 Permalink | Reply
    Tags: "CMS on the lookout for new physics", , , , CERN LHC, From CERN (CH) CMS, , In 2017 CMS recorded a spectacular collision event containing four particle jets in the final state., , , , Small deviations from expectations are appearing in a small number of analyses., The CMS experiment awaits LHC Run 3 to explore several analyses showing small disagreements with theory expectations.   

    From CERN (CH) CMS: “CMS on the lookout for new physics” 

    Cern New Bloc

    Cern New Particle Event

    From CERN (CH) CMS

    The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] Compact Muon Solenoid Detector.

    17 June, 2022
    Piotr Traczyk

    The CMS experiment awaits LHC Run 3 to explore several analyses showing small disagreements with theory expectations.

    With Run 3 of the LHC just around the corner, the LHC experiments are still publishing new results based on the previous runs’ data. Despite no new discoveries being announced, small deviations from expectations are appearing in a small number of analyses. At the current level these deviations can still be attributed to random fluctuations in data, but they indicate regions that need to be investigated closely once the new stream of collisions arrives. Below are a few examples published recently by the CMS collaboration.

    In 2017 CMS recorded a spectacular collision event containing four particle jets in the final state. The invariant mass of all four jets was 8 TeV and the jets could be divided into two pairs with a 1.9 TeV invariant mass each. Such a configuration could be produced if a new particle with an 8 TeV mass was created in the collision of proton beams, and subsequently decayed into a pair of – again, new – particles, with masses of 1.9 TeV. In a new analysis recently published by CMS, a search for such twin pairs of jets with matching invariant masses is performed for data collected up to the end of LHC Run 2. Surprisingly, a second event with similarly striking properties was found, with a 4-jet mass of 8.6 TeV and 2-jet masses of 2.15 TeV. These two events can be clearly seen in the plot below, where the 4-jet events are plotted as a function of the 2-jet and 4-jet mass.

    1
    Number of events observed (colour scale), plotted as a function of four-jet mass and the average mass of the two dijets. The two points in the top right correspond to the two interesting events. (Image: CMS)

    While nearly all observed events with two pairs of jets are produced by strong interactions between the colliding photons, events with such high invariant masses are extremely unlikely. The probability of seeing two events at these masses without any new phenomena being present is of the order of 1 in 20 000, corresponding to a local significance of 3.9σ. While this may appear to be a very strong signal at first, given that the area of masses that are being analysed is large it is important to also look at global significance, which indicates the probability of observing an excess anywhere in the analysed region. For the two events the global significance is only 1.6σ.

    Two other searches for new heavy particles are reporting small excesses in data. In a search for high mass resonances decaying into a pair of W bosons (that then decay into leptons) the highest deviation corresponds to a signal hypothesis with a mass of 650 GeV, with local significance at 3.8σ and global significance of 2.6σ. In a search for heavy particles decaying into a pair of bosons (WW, WZ or other combinations, also including Higgs bosons) that subsequently decay into pairs of jets, the data diverge from expectations in two places. The signal hypothesis is a W’ boson with a mass of 2.1 or 2.9 TeV, decaying into a WZ pair and the highest local significance is 3.6σ, with a global significance of 2.3σ.

    Another new result comes from searches looking for extra Higgs boson particles decaying into tau pairs. For a new particle with a 100 GeV mass there is a small excess seen in the data with 3.1σ local and 2.7σ global significance. Interestingly, this coincides with a similar excess seen by CMS in a previous search for low-mass resonances in the two-photon final state. Another excess is visible in the high-mass range, with the largest deviation from the expectation observed for a mass of 1.2 TeV with a local (global) significance of 2.8σ (2.4σ).

    The tau pair final state was also used to look for hypothetical new particles called leptoquarks. This is of particular interest since leptoquarks could potentially explain the flavour anomalies that have been observed by the LHCb experiment, so if the anomalies are indeed a manifestation of some new phenomena, this would be a way to independently look at these phenomena from a different angle. No excess has been found by CMS so far, but the analysis is only just beginning to be sensitive to the range of leptoquark parameters that could fit the flavour anomalies, so more data is needed to fully explore the leptoquark hypothesis.

    The new LHC data-taking period is set to start in July, at higher energy and with significantly upgraded detectors, promising a fresh stream of data for searches for new phenomena.

    Read more in the CERN Courier and CMS publications here, here and here.

    See the full article here.


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Meet CERN (CH) in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier (CH)

     

  • richardmitnick 8:54 am on June 18, 2022 Permalink | Reply
    Tags: "Harnessing a supercomputer for ATLAS", , , , CERN LHC, , IZUM ATOS BullSequana Vega supercomputer in Slovenia, , , ,   

    From CERN (CH) ATLAS: “Harnessing a supercomputer for ATLAS” 

    European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN]

    Iconic view of the European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire](CH)CERN ATLAS detector

    CERN ATLAS another view Image Claudia Marcelloni ATLAS CERN

    From CERN (CH) ATLAS

    16 June, 2022

    IZUM ATOS BullSequana Vega supercomputer in Slovenia

    1
    Andrej Filipčič (left) and Jan Jona Javoršek (right) from the Jožef Stefan Institute in Ljubljana, Slovenia, next to Vega at the Institute of Information Science in Maribor. (Image: CERN)

    The ATLAS collaboration uses a global network of data centres – the Worldwide LHC Computing Grid – to perform data processing and analysis. These data centres are generally built from commodity hardware to run the whole spectrum of ATLAS data crunching, from reducing the raw data coming out of the detector down to a manageable size to producing plots for publication.

    While the Grid’s distributed approach has proven very successful, the computing needs of the LHC experiments keep expanding, so the ATLAS collaboration has been exploring the potential of integrating high-performance computing (HPC) centres in the Grid’s distributed environment. HPC harnesses the power of purpose-built supercomputers constructed from specialised hardware, and is used widely in other scientific disciplines.

    However, HPC poses significant challenges for ATLAS data processing. Access to supercomputer installations are typically subject to more restrictions than Grid sites and their CPU architectures may not be suitable for ATLAS software. Their scheduling mechanisms favour very large jobs using many thousands of nodes, which is atypical of an ATLAS workflow. Finally, the supercomputer installation may be geographically distant from storage hosting ATLAS data, which may pose network problems.

    Despite these challenges, ATLAS collaborators have been able to successfully exploit HPC over the last few years, including several near the top of the famous Top500 list of supercomputers. Technological barriers were overcome by isolating the main computation from the parts requiring network access, such as data transfer. Software issues were resolved by using container technology, which allows ATLAS software to run on any operating system, and the development of “edge services”, which enables computations to run in an offline mode without the need to contact external services.

    The most recent HPC centre to process ATLAS data is Vega – the first new petascale EuroHPC JU machine, hosted in the Institute of Information Science in Maribor, Slovenia. Vega started operation in April 2021 and consists of 960 nodes, each of which contains 128 physical CPU cores, for a total of 122 800 physical or 245 760 logical cores. To put this in perspective, the total number of cores provided to ATLAS from Grid resources is around 300 000.

    Due to close connections with the community of ATLAS physicists in Slovenia, some of whom were heavily involved in the design and commissioning of Vega, the ATLAS collaboration was one of the first users to be granted official time allocations. This was to the benefit of both the ATLAS collaboration, which could take advantage of a significant extra resource, and Vega, which was supplied with a steady, well-understood stream of jobs to assist in the commissioning phase.

    Vega was almost continually occupied with ATLAS jobs from the moment it was turned on, and the periods where fewer jobs were running were due to either other users on Vega or a lack of ATLAS jobs to submit. This huge additional computing power – essentially doubling ATLAS’s available resources – was invaluable, allowing several large-scale data-processing campaigns to run in parallel. As such, the ATLAS collaboration heads towards the restart of the LHC with a fully refreshed Run 2 data set and corresponding simulations, many of which have been significantly extended in statistics thanks to the additional resources provided by Vega.

    It is a testament to the robustness of ATLAS’s distributed computing systems that they could be scaled up to a single site equivalent in size to the entire Grid. While Vega will eventually be given over to other science projects, some fraction will continue to be dedicated to ATLAS. What’s more, the successful experience shows that ATLAS members (and their data) are ready to jump on the next available HPC centre and fully exploit its potential.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    CERN Courier (CH)

    Quantum Diaries
    QuantumDiaries

    CERN LHC underground tunnel and tube.

    SixTRack CERN LHC particles

     

  • richardmitnick 10:05 pm on June 9, 2022 Permalink | Reply
    Tags: "Probing Higgs self-coupling with boosted Higgs pairs", A key feature of the new result is the use of state-of-the-art machine learning methods which are quickly becoming critical tools in particle physics data analysis., , , CERN LHC, , , , , , This novel Higgs boson jet-tagging approach has resulted in an overall improvement of the boosted Higgs boson pair search sensitivity by more than a factor of 10 over the previous best result at CMS.   

    From The DOE’s Fermi National Accelerator Laboratory-an enduring source of strength for the US contribution to scientific research worldwide. : “Probing Higgs self-coupling with boosted Higgs pairs” 

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    From The DOE’s Fermi National Accelerator Laboratory-an enduring source of strength for the US contribution to scientific research worldwide.

    June 9, 2022
    Artur Apresyan
    Si Xie

    The Higgs boson plays a special role in the Standard Model: It is through the Higgs mechanism that the elementary particles acquire their masses, and their values are determined by the strength of their interaction, also referred to as “coupling,” with the Higgs boson.

    The Higgs boson also interacts with itself, and the strength of this self-coupling has profound implications on the mechanism of the electroweak phase transition the universe underwent shortly after the Big Bang and on the ultimate fate of the universe itself. This self-coupling strength can be measured at the LHC by measuring the rate of double Higgs boson production. Precise measurements of this parameter are among the top priorities of particle physics and the LHC physics program.

    A new search for Higgs boson pairs (HH) with the CMS experiment has pushed us closer than ever to a measurement of the Higgs boson self-coupling. CMS physicists searched for two so-called boosted Higgs bosons that have momentum so large that the decay products of each Higgs boson merge within a single jet, i.e., into a single conical spray of particles.

    1
    Figure 1: A candidate event in which two Higgs bosons produced at large transverse momenta decay into collimated bottom quark-antiquark pairs, represented by the orange cones. The event signature is consistent with gluon fusion production of a Higgs boson pair. Image: CMS Collaboration.

    A candidate event captured by the CMS detector is shown in Fig. 1. New results from the search were recently published by the CMS collaboration, which show this to be the most sensitive single channel at CMS in its search for the double Higgs boson process.

    The data are found to agree with the background-only hypothesis, as shown in Fig. 2, and an observed (expected) upper limit at 95% confidence level is set at 9.9 (5.1) times the Standard Model expectation. Moreover, the search makes a novel measurement of the vector-boson fusion production mode of a pair of Higgs bosons, and obtain for the first time ever, at more than 99.99% confidence level, a non-zero value of the coupling strength between a pair of Higgs bosons and a pair of electroweak vector bosons.

    2
    Figure 2: The distributions for data, background and signal contributions for the sub-leading jet mass. The lower panel shows the ratio of the data and the total prediction, with its uncertainty represented by the shaded band. Image: CMS Collaboration.

    A key feature of the new result is the use of state-of-the-art machine learning methods which are quickly becoming critical tools in particle physics data analysis. The current search uses graph neural networks trained on kinematic and topological data of highly granular particle constituents of jets to optimally distinguish a boosted jet produced by a Higgs boson from similar jets produced by background processes. This novel Higgs boson jet-tagging approach has resulted in an overall improvement of the boosted Higgs boson pair search sensitivity by more than a factor of 10 over the previous best result, thereby making this channel the most sensitive one at CMS.

    As the focus turns to the High-Luminosity LHC (HL-LHC), the boosted Higgs pair channel may play a key role in the future observation of the HH process. The significance for observing HH production at the end of HL-LHC has been projected to be close to 4σ. With the inclusion of this highly sensitive boosted HH channel, in combination with all other HH searches at the LHC, it is possible that the golden 5σ threshold for observation of HH would be achieved at the HL-LHC.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The DOE’s Fermi National Accelerator Laboratory, located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been operated by the Fermi Research Alliance, a joint venture of the University of Chicago, and the Universities Research Association. Fermilab is a part of the Illinois Technology and Research Corridor.

    Fermilab’s Tevatron was a landmark particle accelerator; until the startup in 2008 of the The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL)[CERN] Large Hadron Collider(CH) near Geneva, Switzerland, it was the most powerful particle accelerator in the world, accelerating antiprotons to energies of 500 GeV, and producing proton-proton collisions with energies of up to 1.6 TeV, the first accelerator to reach one “tera-electron-volt” energy. At 3.9 miles (6.3 km), it was the world’s fourth-largest particle accelerator in circumference. One of its most important achievements was the 1995 discovery of the top quark, announced by research teams using the Tevatron’s CDF and DØ detectors. It was shut down in 2011.

    In addition to high-energy collider physics, Fermilab hosts a series of fixed-target and neutrino experiments, such as The MicroBooNE (Micro Booster Neutrino Experiment),

    NOνA (NuMI Off-Axis νe Appearance)

    and Seaquest

    .

    Completed neutrino experiments include MINOS (Main Injector Neutrino Oscillation Search), MINOS+, MiniBooNE and SciBooNE (SciBar Booster Neutrino Experiment).

    The MiniBooNE detector was a 40-foot (12 m) diameter sphere containing 800 tons of mineral oil lined with 1,520 phototube detectors. An estimated 1 million neutrino events were recorded each year.

    SciBooNE sat in the same neutrino beam as MiniBooNE but had fine-grained tracking capabilities. The NOνA experiment uses, and the MINOS experiment used, Fermilab’s NuMI (Neutrinos at the Main Injector) beam, which is an intense beam of neutrinos that travels 455 miles (732 km) through the Earth to the Soudan Mine in Minnesota and the Ash River, Minnesota, site of the NOνA far detector.

    The ICARUS neutrino experiment was moved from CERN to Fermilab.

    In the public realm, Fermilab is home to a native prairie ecosystem restoration project and hosts many cultural events: public science lectures and symposia, classical and contemporary music concerts, folk dancing and arts galleries. The site is open from dawn to dusk to visitors who present valid photo identification.

    Asteroid 11998 Fermilab is named in honor of the laboratory.

    The DOE’s Fermi National Accelerator Laboratory campus.

    The DOE’s Fermi National Accelerator Laboratory(US)/MINERvA. Photo Reidar Hahn.

    The DOE’s Fermi National Accelerator LaboratoryDAMIC | The Fermilab Cosmic Physics Center.

    The DOE’s Fermi National Accelerator LaboratoryMuon g-2 studio. As muons race around a ring at the Muon g-2 studio, their spin axes twirl, reflecting the influence of unseen particles.

    The DOE’s Fermi National Accelerator Laboratory Short-Baseline Near Detector under construction.

    The DOE’s Fermi National Accelerator Laboratory Mu2e solenoid.

    The Dark Energy Camera [DECam], built at The DOE’s Fermi National Accelerator Laboratory.

    Weston, Illinois, was a community next to Batavia voted out of existence by its village board in 1966 to provide a site for Fermilab.

    The laboratory was founded in 1969 as the National Accelerator Laboratory; it was renamed in honor of Enrico Fermi in 1974. The laboratory’s first director was Robert Rathbun Wilson, under whom the laboratory opened ahead of time and under budget. Many of the sculptures on the site are of his creation. He is the namesake of the site’s high-rise laboratory building, whose unique shape has become the symbol for Fermilab and which is the center of activity on the campus.

    After Wilson stepped down in 1978 to protest the lack of funding for the lab, Leon M. Lederman took on the job. It was under his guidance that the original accelerator was replaced with the Tevatron, an accelerator capable of colliding protons and antiprotons at a combined energy of 1.96 TeV. Lederman stepped down in 1989. The science education center at the site was named in his honor.

    The later directors include:

    John Peoples, 1989 to 1996
    Michael S. Witherell, July 1999 to June 2005
    Piermaria Oddone, July 2005 to July 2013
    Nigel Lockyer, September 2013 to the present

    Fermilab continues to participate in the work at the Large Hadron Collider (LHC); it serves as a Tier 1 site in the Worldwide LHC Computing Grid and hosts 1000 U.S. scientists who work on the CMS project.

    FNAL Icon

     

  • richardmitnick 10:25 am on May 27, 2022 Permalink | Reply
    Tags: "'Quark Matter 2022' New Results from RHIC and LHC—Plus Plans for the Future", , , CERN LHC, , High-energy heavy ion physics, , , , , RHIC and the LHC collide heavy ions which are the nuclei of heavy atoms such as gold and lead that have been stripped of their electrons., RHIC’s "STAR" experiment, The ATLAS detector project at CERN’s LHC, , The Electron-Ion Collider (EIC) at RHIC, The interplay of theory and experiment is essential to advancing our understanding of how quarks and gluons interact., , ,   

    From The DOE’s Brookhaven National Laboratory: “‘Quark Matter 2022’ New Results from RHIC and LHC—Plus Plans for the Future” 

    From The DOE’s Brookhaven National Laboratory

    May 24, 2022
    Karen McNulty Walsh
    kmcnulty@bnl.gov

    Meeting highlights include detailed descriptions of fundamental matter and explorations of intriguing physics.

    1

    Theoretical and experimental physicists from around the world gathered last month at Quark Matter 2022 to discuss new developments in high energy heavy ion physics. The “29th International Conference on Ultrarelativistic Heavy-Ion Collisions” took place April 4-10, 2022, with both in-person talks in Kraków, Poland, and many participants logging in remotely from around the globe.

    Highlights included a series of presentations and discussions about the latest findings from heavy ion research facilities—notably the Relativistic Heavy Ion Collider (RHIC) [below] at the U.S. Department of Energy’s Brookhaven National Laboratory and the Large Hadron Collider [below]at the European Center for Nuclear Research (CERN)—as well as future research directions for the field.

    During parts of their research runs, RHIC and the LHC collide heavy ions, which are the nuclei of heavy atoms such as gold and lead that have been stripped of their electrons. These highly energetic, nearly light speed head-on collisions generate temperatures more than 250,000 times hotter than the center of the sun and set free the innermost building blocks of the nuclei—the quarks and gluons that make up protons and neutrons.

    The resulting nearly-perfect liquid, the “quark-gluon plasma” (QGP), reflects the conditions of the very early universe nearly 14 billion years ago—an era just a microsecond after the Big Bang before protons and neutrons first formed. By tracking particles that stream out of these collisions, scientists can expand their understanding how matter evolved from the hot quark soup into everything made of atoms in the universe today.

    “Quark Matter is the major event for physicists in our field,” said Peter Steinberg, a nuclear physicist at Brookhaven Lab who participates in experiments at both RHIC and the LHC and attended the meeting virtually from his home in Brooklyn, New York. “Held approximately every 18 months, it’s where we usually first share and hear about preliminary results, discuss them with our colleagues, and always learn from one another so that we can strengthen our analyses and experimental approaches.”

    Theorists also presented their latest studies including analyses and interpretations of data.

    “The field of high-energy heavy ion physics has witnessed major advances through close collaborations between theory and experiment,” said Haiyan Gao, Associate Laboratory Director (ALD) for Nuclear and Particle Physics (NPP) at Brookhaven Lab. “This interplay of theory and experiment is essential to advancing our understanding of how quarks and gluons interact to build of the properties and structure of the matter that makes up our world.”

    In addition, several presentations highlighted how results from (and improvements to) heavy-ion experiments at RHIC and the LHC, as well as new theoretical approaches, are paving the way for exciting results to come. That future includes the start of Run 3 at the LHC, installation of the sPHENIX detector at RHIC for the experimental run starting in 2023, and eventually the Electron-Ion Collider (EIC) [below], a brand-new nuclear physics research facility in the preliminary design stage at Brookhaven that is expected to come online early in the next decade.

    As is customary for Quark Matter meetings, the day prior to the start of the detailed scientific presentations was dedicated to welcoming students to the field of heavy-ion physics.

    “Talks covering the history and goals of heavy ion physics during the student day are designed to encourage undergraduates and graduate students to join us,” Steinberg said.

    213 students from undergraduate to PhD levels and 115 early-career postdoctoral fellows registered for the student day, representing institutions in Europe, Asia, North America, South America, and more. Approximately 20 percent of the total were female, with slightly higher female representation (23 percent) in the student group.

    “Projects like RHIC and the LHC and the future EIC have been designed from the start as truly international endeavors, seeking to serve the worldwide nuclear and high-energy physics communities,” said Gao. “It is particularly exciting to see so many young people from different backgrounds eager to learn about our research and potentially become the next generation of leaders for these fields. We also recognize that we still have a long way to go to have a more diverse pipeline in our field.”

    Highlights from The STAR detector [below]

    Brookhaven Lab physicist Prithwish Tribedy presented the highlights from RHIC’s STAR experiment. These included results from RHIC’s isobar collisions. The isobar collisions were designed to explore the effects of the magnetic field generated by colliding ions.

    The first isobar analysis looking for evidence of something called the chiral magnetic effect, released last summer, didn’t turn out as expected. Those results indicated that there might be “background” processes that had not yet been considered. Still, the results presented at QM22 demonstrate a definitive difference in the initial magnetic field strength produced in the two types of collisions analyzed, and provide new background estimates for future analyses. The isobar collisions are also offering insight into how the shape of colliding nuclei might influence how particles emerge from these collisions.

    Several STAR results helped elucidate characteristics of the phase transition from hadrons (composite particles made of quarks, such as protons and neutrons) to quark-gluon plasma. Tribedy pointed to results showing how that transition happens at different energies. He also discussed how STAR physicists are using results from RHIC’s Beam Energy Scan (BES) to map out features of the nuclear phase diagram and search for a critical point on that plot of nuclear phases.

    New data presented on results from 3.85 GeV giga-electron-volt (GeV) collisions of gold ions with a fixed target are consistent with a model calculation which does not have a critical point. With high-statistics data from BES-II, STAR will really explore the critical behavior in the 3-19.6 GeV energy region.

    There were also results tracking rare “hypernuclei,” including the first observation of anti-hyper-hydrogen-4. These nuclei contain particles called hyperons, which have at least one “strange” quark, and thus they offer insight into the properties of neutron stars where strange particles are widely thought to be more abundant than they are in normal matter. New STAR results also confirm that the temperature of the QGP is hotter than the sun, and provide a deeper understanding of its detailed properties.

    Tribedy ended by describing how new forward detectors have expanded STAR’s capabilities, noting that these forward upgrades will open paths to study the microstructure of the QGP and enable measurements that will bridge the RHIC and EIC science programs. And he pointed attendees to the many later QM22 talks and posters that would elaborate on the details of the topics he’d introduced.

    “The rich and diverse physics programs at STAR come from the versatile machine and detector capabilities at RHIC, and the hard work and intellectual contributions of collaborators and scientists from all over the world,” said Lijuan Ruan, a physicist at Brookhaven and co-spokesperson for STAR.

    New PHENIX [below] analyses

    RHIC’s PHENIX experiment completed operations in 2016, but members of the collaboration are still actively analyzing its data. At QM22, Sanghoon Lim of Pusan National University presented an overview of the collaboration’s latest results.

    Lim summarized a wide range of analyses exploring collisions of different types of ions—from “small” protons, deuterons, and helium ions to larger nuclei such as copper, gold, and uranium. These experiments provide a detailed understanding of how features of the nuclear matter created in collisions (and particle interactions with that medium) change with the size of the system.

    The newest results further confirm a wide range of data from both Brookhaven and CERN including a string of successive results from PHENIX showing that QGP can be created even in collisions of small particles with larger nuclei. Low-energy photons (particles of light emitted from the QGP) provide a way to probe the temperature of the medium produced and have shown a smooth transition to hot QGP temperatures in both small and large systems.

    QM22 also featured long-awaited measurements of high-energy direct photons emitted from head-on and more peripheral deuteron-gold collisions. These measurements are helping scientists understand how much hadrons created in these small systems are being modified by their interactions with the QGP.

    Meanwhile the collisions of large nuclei are providing detailed information about the QGP, such as how jets of particles produced in the collisions lose energy as they traverse it. PHENIX physicists extracted new observations by looking at how the angles between particles that make up a jet are correlated with one another. These analyses allow the scientists to probe how the distribution of particles associated with jets might be modified—for example, “quenched” as they lose energy through their interactions with the QGP.

    “We are using a technique to study jets that we have been using since the early days of RHIC, but we are now extracting additional quantities from the data that are also being extracted from jet measurements at the LHC,” said Megan Connors, a PHENIX collaborator from Georgia State University (GSU) who presented these results at QM22. “These additional analyses can further constrain theoretical models and improve our understanding of the jet quenching process.”

    In addition, PHENIX presented measurements of heavy quarks to study how quarks of different masses lose energy to the QGP as they get caught up in its flow. Final low-energy photon results were also shown. These results zero in on the temperature of the QGP and its evolution as the QGP expands and cools with higher precision than any previous measurements. Lim noted that PHENIX will continue to analyze data, including from 35 billion gold-gold collision events recorded in 2014 and 2016, to further elucidate these properties. And he pointed to a list of newly published and submitted papers—and detailed QM22 talks—for anyone interested in learning more about these results.

    “There is no question that PHENIX measurements will continue to play an important role in our field and impact our understanding from small to large collision systems,” GSU’s Connors said.

    Brookhaven ATLAS [below] results of note

    ATLAS, one of the detectors at the LHC, presented a wide range of results from lead-lead collisions, covering both well-established diagnostics of the QGP as well as an extensive array of new measurements using photons (particles of light) that are present in the intense electromagnetic fields surrounding the lead ions.

    ATLAS released a new set of measurements showing how the QGP responds to different types of particle jets produced in lead-lead collisions. By analyzing these data, scientists are trying to distinguish between quarks that come in different “flavors,” as well as between quark and gluon jets. There were also exciting new results exploring how pairs of back-to-back jets (typically referred to as “dijets”) are affected by traversing the plasma. These new findings were a major update of the very first ATLAS result submitted only weeks after the first lead beams collided in the LHC in 2010.

    Timothy Rinn, a Brookhaven Lab postdoctoral associate who presented these results, said, “This result provides new insight into the nature of how jets lose energy, or become ‘quenched,’ in dijet events. Many scientists had developed an explanation for earlier jet quenching data based on the belief that the higher energy jet was formed near the surface, and thus must have suffered much less energy loss, while the lower energy jet traveled through a longer distance in the QGP, losing energy along the way. The recent result suggests that both jets in the event typically experience significant energy loss, and pairs of jets where both have a similar energy are observed much less often than expected. These exciting new results are already of great interest to the theoretical community developing sophisticated models of this phenomenon.”

    ATLAS also presented a major new result on the “anomalous magnetic moment” of the tau lepton. This is a measure of how tau particles, the heaviest cousin of the electron, “wobble” in a magnetic field, and is commonly referred to as “g-2.” As with measurements of the g-2 for particles called muons (another electron cousin, studied at both Brookhaven and more recently at Fermi National Accelerator Laboratory), seeing deviations from tau leptons’ predicted g-2 value could be an indication that some yet-to-be-discovered particles—physics “beyond the standard model”—are affecting the results. While the ATLAS measurements so far show no significant difference, the results were based on only a small number of events with large uncertainties. Much more data will be collected in LHC Runs 3 and 4, which could be much more exciting.

    Plans for sPHENIX and EIC physics

    On the final day of the conference, Brookhaven Lab physicist and co-spokesperson of the sPHENIX collaboration David Morrison gave an overview of “The near- and mid-term future of RHIC, EIC and sPHENIX.” Morrison noted how RHIC is well on its way to achieving goals spelled out in the 2015 Long Range Plan for Nuclear Science. These included completing the Beam Energy Scan to map out the phases of quark matter and probing the properties of QGP at shorter and shorter length scales at both RHIC and the LHC.

    4
    Dave Morrison, Brookhaven Lab physicist and co-spokesperson for the sPHENIX collaboration, in front of the sPHENIX detector during an early stage of assembly.

    The latter goal will be a central focus of sPHENIX, a detector currently under construction at RHIC with the anticipation of taking its first data early next year. During RHIC’s final three years of operation, before conversion of some of its key components into the EIC begins, sPHENIX will collect and analyze data to make precision measurements of jets of particles and bound quark states with different masses, while recent STAR upgrades continue to provide insight into the detailed properties of the QGP.

    As described in other talks at QM22, some of those STAR components have also been contributing to a scientific goal that will be a key feature of the EIC—mapping out the internal distribution of quarks and gluons that make up protons and neutrons. The technique for making those measurements at RHIC uses one proton beam’s upward spin alignment as a frame of reference for tracking particle interactions at a wide range of angles from that reference point.

    Other recent advances using particles of light that surround the speeding gold ions at RHIC will help pave the way for the EIC science program. In ultraperipheral collisions, where the gold ions graze by one another without direct ion-to-ion impact, the photons surrounding the ions can interact to produce interesting physics—and also serve as probes of the structure within the nuclear particles. At the EIC, speeding electrons will emit virtual photons for probing the inner components of protons and heavier nuclei.

    “At RHIC, we also use these ‘photonuclear’ events to study how quarks and gluons contribute to ‘baryon number’—a quantum number that adds up to one in particles made of three quarks—and how that number is affected when these three-quark particles (including protons and neutrons) interact with matter,” said STAR co-spokesperson Ruan. This analysis was done by Nicole Lewis, a postdoctoral fellow in the STAR group at Brookhaven Lab, whose poster contribution was one of 10 (out of 500) selected to be featured in a flash talk at the conference.

    “It is wonderful to see so many new results presented at Quark Matter 2022,” concluded Brookhaven Lab NPP ALD Gao. “It takes an enormous effort to prepare for this meeting—and to run the facilities that produce the data presented there. The thousands of physicists, engineers, and technicians at RHIC, the LHC, and their detectors all deserve our sincere gratitude for making this great science possible.”

    RHIC operations are funded by the DOE Office of Science, which runs the machine as a User Facility open to an international community of physicists. Each collaboration receives additional funding from a range of international partners and agencies. Brookhaven’s involvement in research at the LHC and the EIC Project are also funded by the DOE Office of Science.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Brookhaven Campus

    One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

    Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5,300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

    BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

    Major programs

    Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

    Nuclear and high-energy physics
    Physics and chemistry of materials
    Environmental and climate research
    Nanomaterials
    Energy research
    Nonproliferation
    Structural biology
    Accelerator physics

    Operation

    Brookhaven National Lab was originally owned by the Atomic Energy Commission(US) and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc.(AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

    Foundations

    Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

    Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

    On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

    Research and facilities

    Reactor history

    In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

    Accelerator history

    In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

    BNL Cosmotron 1952-1966.

    The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

    BNL Alternating Gradient Synchrotron (AGS).

    The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

    In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

    The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

    The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

    BNL National Synchrotron Light Source.

    After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider(CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

    On January 9, 2020, It was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] (US) as the future Electron–ion collider (EIC) in the United States.

    Brookhaven Lab Electron-Ion Collider (EIC) to be built inside the tunnel that currently houses the RHIC.

    In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

    Other discoveries

    In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

    Major facilities

    Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

    Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

    BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

    Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
    Accelerator Test Facility, generates, accelerates and monitors particle beams.
    Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

    Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

    Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
    NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

    Off-site contributions

    It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

    The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] map.

    Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN] ATLAS detector.

    It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN] near Geneva, Switzerland.

    Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

    DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

    Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

    Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .


    BNL Center for Functional Nanomaterials.

    BNL National Synchrotron Light Source II.

    BNL NSLS II.

    BNL Relative Heavy Ion Collider Campus.

    BNL/RHIC Star Detector.

    BNL/RHIC Phenix detector.

     

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