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  • richardmitnick 4:47 pm on January 9, 2020 Permalink | Reply
    Tags: "Department of Energy picks New York over Virginia for site of new particle collider", , , HEP, , , , ,   

    From BNL via Science Magazine: “Department of Energy picks New York over Virginia for site of new particle collider” 

    From Brookhaven National Lab

    via

    AAAS
    Science Magazine

    Jan. 9, 2020
    Adrian Cho

    Nuclear physicists’ next dream machine will be built at Brookhaven National Laboratory in Upton, New York, officials with the Department of Energy (DOE) announced today. The Electron-Ion Collider (EIC) will smash a high-energy beam of electrons into one of protons to probe the mysterious innards of the proton. The machine will cost between $1.6 billion and $2.6 billion and should be up and running by 2030, said Paul Dabbar, DOE’s undersecretary for science, in a telephone press briefing.

    6
    This schematic shows how the EIC will fit within the tunnel of the Relativistic Heavy Ion Collider (RHIC, background photo), reusing essential infrastructure and key components of RHIC.

    3
    Electrons will collide with protons or larger atomic nuclei at the Electron-Ion Collider to produce dynamic 3-D snapshots of the building blocks of all visible matter.

    7
    The EIC will allow nuclear physicists to track the arrangement of the quarks and gluons that make up the protons and neutrons of atomic nuclei.

    “It will be the first brand-new greenfield collider built in the country in decades,” Dabbar said. “The U.S. has been at the front end in nuclear physics since the end of the Second World War and this machine will enable the U.S. to stay at the front end for decades to come.”

    The site decision brings to a close the competition to host the machine. Physicists at DOE’s Thomas Jefferson National Accelerator Facility in Newport News, Virginia, had also hoped to build the EIC.

    Protons and neutrons make up the atomic nucleus, so the sort of work the EIC would do falls under the rubric of nuclear physics. Although they’re more common than dust, protons remain somewhat mysterious. Since the early 1970s, physicists have known that each proton consists of a trio of less massive particles called quarks. These bind to one another by exchanging other quantum particles called gluons.

    However, the detailed structure of the proton is far more complex. Thanks to the uncertainties inherent in quantum mechanics, its interior roils with countless gluons and quark-antiquark pairs that flit in and out of existence too quickly to be directly observed. And many of the proton’s properties—including its mass and spin—emerge from that sea of “virtual” particles. To determine how that happens, the EIC will use its electrons to probe the protons, colliding the two types of particles at unprecedented energies and in unparalleled numbers.

    Researchers at Jefferson lab already do similar work by firing their electron beam at targets rich with protons and neutrons. In 2017, researchers completed a $338 million upgrade to double the energy of the lab’s workhorse, the Continuous Electron Beam Accelerator Facility.

    3
    4
    Continuous Electron Beam Accelerator Facility

    With that electron accelerator in hand, Jefferson lab researchers had hoped to build the EIC by adding a new proton accelerator.

    Brookhaven researchers have studied a very different type of nuclear physics. Their Relativistic Heavy Ion Collider (RHIC) [below] collides nuclei such as gold and copper to produce fleeting puffs of an ultrahot plasma of free-flying quarks and gluons like the one that filled the universe in the split second after the big bang. The RHIC is a 3.8-kilometer-long ring consisting of two concentric and counter-circulating accelerators. Brookhaven researchers plan to make the EIC by using one of the RHIC’s rings to accelerate the protons and to add an electron accelerator to the complex.

    To decide which option to take, DOE officials convened an independent EIC site selection committee, Dabbar says. The committee weighed numerous factors, including the relative costs of the rival plans, he says. Proton accelerators are generally larger and more expensive than electron accelerators.

    The Jefferson lab won’t be left out in the cold, Dabbar says. Researchers there have critical expertise in, among other things, making the superconducting accelerating cavities that will be needed for the new collider. So, scientists there will participate in designing, building, and operating the new collider. “We certainly look forward to [the Jefferson lab] taking the lead in these areas,” Dabbar says.

    The site decision does not commit DOE to building the EIC. The project must still pass several milestones before researchers can being construction—including the approval of a detailed design, cost estimate, and construction schedule. That process can take a few years. However, the announcement does signal the end for the RHIC, which has run since 1999. To make way for the new collider, the RHIC will shut down for good in 2024, Dabbar said at the briefing.

    The decision on a machine still 10 years away reflects the relative good times for DOE science funding, Dabbar says. “We’ve been able to start on every major project that’s been on the books for years.” DOE’s science budget is up 31% since 2016—in spite of the fact that under President Donald Trump, the White House has tried to slash it every year.

    See the full article here .


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    BNL Center for Functional Nanomaterials

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), 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.
    i1

     
  • richardmitnick 10:57 am on January 9, 2020 Permalink | Reply
    Tags: "New open release allows theorists to explore LHC data in a new way", , , HEP, , , , The first open release of full analysis likelihoods from an LHC experiment.   

    From CERN ATLAS: “New open release allows theorists to explore LHC data in a new way” 

    CERN/ATLAS detector

    CERN ATLAS Higgs Event

    CERN ATLAS another view Image Claudia Marcelloni ATLAS CERN

    From CERN ATLAS

    9 January, 2020
    Katarina Anthony

    The ATLAS collaboration releases full analysis likelihoods, a first for an LHC experiment.

    1
    Explore ATLAS open likelihoods on the HEPData platform. (Image: CERN)

    What if you could test a new theory against LHC data? Better yet, what if the expert knowledge needed to do this was captured in a convenient format? This tall order is now on its way from the ATLAS collaboration, with the first open release of full analysis likelihoods from an LHC experiment.

    “Likelihoods allow you to compute the probability that the data observed in a particular experiment match a specific model or theory,” explains Lukas Heinrich, CERN research fellow working for the ATLAS Experiment. “Effectively, they summarise every aspect of a particular analysis, from the detector settings, event selection, expected signal and background processes, to uncertainties and theoretical models.” Extraordinarily complex and critical to every analysis, likelihoods are one of the most valuable tools produced at the LHC experiments. Their public release will now enable theorists around the world to explore ATLAS data in a whole new way.

    The ATLAS open likelihoods are available on HEPData, an open-access repository for experimental particle physics data. The first open likelihoods released were for a search for supersymmetry in proton–proton collision events containing Higgs bosons, numerous jets of b-quarks and missing transverse momentum. “While ATLAS had published likelihood scans focused on the Higgs boson in 2013, those did not expose the full complexity of the measurements,” says Kyle Cranmer, Professor at New York University. “We hope this first release – which provides the full likelihoods in all their glory – will form a new communication bridge between theorists and experimentalists, enriching the discourse between the communities.”

    The search for new physics will benefit significantly from open likelihoods. “If you’re a theorist developing a new idea, your first question is likely: ‘Is my model already excluded by experiments at the LHC?’” says Giordon Stark, postdoctoral scholar at SCIPP, UC Santa Cruz. “Until now, there was no easy way to answer this.”

    2
    Likelihoods are an essential link between theory and ATLAS data. (Image: K. Cranmer/ATLAS)

    “We plan to make the open release of likelihoods a regular part of our publication process, and have already made them available from a search for the direct production of tau slepton pairs,” says Laura Jeanty, ATLAS Supersymmetry working group convenor. “Over the coming months, we aim to collect feedback from theorists outside the collaboration to best understand how they are using this new resource to further refine future releases.”

    Read more on the ATLAS website.

    See the full article here .


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    CERN Courier

    Quantum Diaries
    QuantumDiaries

    CERN map


    CERN LHC Grand Tunnel
    CERN LHC particles

     
  • richardmitnick 11:40 am on December 14, 2019 Permalink | Reply
    Tags: , , Femtoscopy, HEP, Hyperons, , , ,   

    From Symmetry: “Neutron star particles go under the LHC microscope” 

    Symmetry Mag
    From Symmetry<

    12/12/19
    Mordechai Rorvig

    1
    NASA/CXC/SAO

    Researchers on the ALICE experiment are uncovering the properties of elusive hyperon particles hypothesized to be found inside neutron stars.

    CERN/ALICE Detector

    Scientists know a thing or two about neutron stars, the compacted remains of massive stars that have burned out.

    They know that they’re about 95% made up of neutrons. They know that they’re generally 13 to 16 miles in diameter. Scientists know that, even though neutron stars are a thousandth the size of the Earth, they’re more massive than the sun. And the closest one they know of is about 500 light-years away.

    There’s also a lot they don’t know.

    “Neutron stars are the most dense objects in the universe,” says Laura Fabbietti, a physicist on the ALICE experiment and a professor at Technische Universität München in Germany. “And we don’t know what’s inside because we cannot fly there and look inside.”

    But scientists at CERN have found a way to learn more about the interior of neutron stars from a location that is much safer and easier to access: the Large Hadron Collider, right here on Earth.

    CERN/LHC Map

    Formed under pressure

    For neutron stars, gravity becomes extremely strong, approaching that of black holes. The force of it packs their matter down to high density.

    Neutron stars must be composed of matter that can withstand this pressure. And nature rearranges any matter that can’t into new matter that can.

    Iron, for example, is thought to be a component of the neutron star’s crust, where the pressure is lightest. Slightly deeper in, scientists think that iron atoms get crushed into heavier atoms. Even deeper, the electrons and protons that hold together atoms get crushed into neutrons. In the very interior of the star, those neutrons might get crushed into particles called hyperons.

    Hyperons are akin to heavier versions of neutrons, both of which are composed of quarks.

    Standard Model of Particle Physics

    There are six types of quarks in total. Most of the matter humans interact with, except for electrons, is built with the lightest of these quarks: up and down quarks. Neutrons, for example, are made of one up quark and two down quarks.

    The next heaviest quark is called the strange quark. Replacing an up or down quark in a neutron with a heavier strange quark yields a hyperon.

    Luckily for scientists who want to study this form of matter, all the different kinds of hyperons—different combinations of up, down and strange quarks—are produced in collisions in the Large Hadron Collider.

    Their lives are different there. In experiments at the LHC, hyperons last for less than a billionth of a second before decaying into other, lighter particles. In neutron stars, however, hyperons should be stable. Because they would be pressed in so close together, there would be no room for their decay products to form.

    Their short laboratory lifespans have made hyperons historically difficult to identify and study. But the unique capabilities of the ALICE detector at the LHC allowed Fabbietti and her research team to accurately identify the hyperon decay products and track those products back to their hyperon source. An upgrade of the ALICE detector will soon allow researchers to collect even more hyperon data.

    “We’re hungry for statistics, hungry for data,” says Bernhard Hohlweger, who led analysis to identify the Xi- (pronounced zai-minus) hyperon, a hyperon with a negative electric charge. “We use everything we can get our hands on.”

    Moving in pairs

    Fabbietti’s group didn’t want just to find hyperons, though; they wanted to learn more about what they do. If they could understand hyperon motion in the ALICE detector, then they could hypothesize the way that hyperons might behave while inaccessibly buried in the universe’s densest stars.

    The chief unknown for the ALICE researchers was the way that hyperons interact with the strong force, which binds quarks together and controls particle motion at small scales. Each kind of hyperon has its own unique mathematical function called a “potential” that explains how the hyperon interacts with the strong force to move.

    “For different particle interactions, there are different potentials,” says Anthony Timmins, a member of the ALICE collaboration and a professor at the University of Houston. Timmins recently presented results on proton Xi- hyperon interactions at the annual Division of Particles & Fields meeting in Boston in July.

    To figure out the Xi- hyperon potential, Fabbieti’s group first looked at a different kind of particle that comes from collisions in the LHC: the proton. Protons have never been observed to decay like short-lived LHC hyperons—and may not decay at all—making them easier to understand by comparison. On top of that, researchers already knew the proton potentials, and that those potentials cause protons to attract or repel each other based on how far apart they are.

    The scientists observed that pairs of protons coming out of collisions tend to be pulled into parallel trajectories by their strong-force potentials. They used that observation and a method called femtoscopy to infer the approximate size of the particles’ collision zone.

    Using femtoscopy, which relates particle motions and particle potentials to the size of collision zones, is like watching debris fly out of an explosion to figure out how big an explosive device must have been. (Only in this case, the debris also interact through the strong force.)

    Having analyzed the proton pairs, the researchers then looked at pairs of protons and hyperons coming out of particle collisions. They again observed parallel motions, indicating an attractive strong-force potential at work. Because they knew the size of the collision zone from the proton pairs, the they could solve for the only unknown: the hyperon potential.

    To understand and quantify this measured potential, next they needed a prediction from theory.

    Stiffening stars

    As it turned out, scientists had recently predicted what these potentials would be. They did it theoretically through simulations of quarks.

    These simulation models are general in nature, relying only on knowledge of quarks, with no specific customizations for the LHC experiments. To the researchers’ surprise and excitement, the simulation results and the measurements from Fabbietti’s group matched.

    “If we do some honest calculations and we get the result, then this result should be realized in nature,” says Tetsuo Hatsuda, a program director at the RIKEN institute in Japan, who helped lead the simulation program. And in this case, “the result was realized in nature.”

    Using these precisely calculated potentials, Takashi Inoue from Hatsuda’s HAL QCD collaboration showed how Xi- hyperons should interact with neutrons in neutron star matter. Hyperons and neutrons were found to repel, unlike hyperons and protons measured in the ALICE detector. This repulsion would make neutron stars stiffer and more resistant to gravitational forces if hyperons were present.

    The baton now goes to astrophysicists, who can compare predicted neutron star stiffness with their observations to help answer the question whether hyperons do indeed exist inside stars.

    Fabbietti and her group plan to continue analyzing more data for different kinds of hyperons, with better precision. Fabbietti says that now “this is a factory of results,” results that show how the 17-mile, underground ring of the LHC can act as a microscope into the stars.

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 4:25 pm on December 4, 2019 Permalink | Reply
    Tags: "Discovering the Top Quark", , , FNAL Tevatron CDF, HEP, , , ,   

    From particlebites: “Discovering the Top Quark” 

    particlebites bloc

    From particlebites

    December 3, 2019
    Adam Green

    This post is about the discovery of the most massive quark in the Standard Model, the Top quark. Below is a “discovery plot” [1] from the Collider Detector at Fermilab collaboration (CDF). Here is the original paper [Physical Review Letters].

    FNAL/Tevatron CDF detector

    FNAL/Tevatron tunnel

    FNAL/Tevatron map

    1
    This plot confirms the existence of the Top quark. Let’s understand how.

    For each proton collision that passes certain selection conditions, the horizontal axis shows the best estimate of the Top quark mass. These selection conditions encode the particle “fingerprint” of the Top quark. Out of all possible proton collisions events, we only want to look at ones that perhaps came from Top quark decays. This subgroup of events can inform us of a best guess at the mass of the Top quark. This is what is being plotted on the x axis.

    On the vertical axis are the number of these events.

    The dashed distribution is the number of these events originating from the Top quark if the Top quark exists and decays this way. This could very well not be the case.

    The dotted distribution is the background for these events, events that did not come from Top quark decays.

    The solid distribution is the measured data.

    To claim a discovery, the background (dotted) plus the signal (dashed) should equal the measured data (solid). We can run simulations for different top quark masses to give us distributions of the signal until we find one that matches the data. The inset at the top right is showing that a Top quark of mass of 175GeV best reproduces the measured data.

    Taking a step back from the technicalities, the Top quark is special because it is the heaviest of all the fundamental particles. In the Standard Model, particles acquire their mass by interacting with the Higgs. Particles with more mass interact more with the Higgs. The Top mass being so heavy is an indicator that any new physics involving the Higgs may be linked to the Top quark.

    References / Further Reading

    [1] – Observation of Top Quark Production in pp Collisions with the Collider Detector at Fermilab – This is the “discovery paper” announcing experimental evidence of the Top.

    [2] – Observation of tt(bar)H Production [Physical Review Letters]– Who is to say that the Top and the Higgs even have significant interactions to lowest order? The CMS collaboration finds evidence that they do in fact interact at “tree-level.”

    [2] – The Perfect Couple: Higgs and top quark spotted together – This article further describes the interconnection between the Higgs and the Top.

    See the full article here .

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    What is ParticleBites?

    ParticleBites is an online particle physics journal club written by graduate students and postdocs. Each post presents an interesting paper in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.

    The papers are accessible on the arXiv preprint server. Most of our posts are based on papers from hep-ph (high energy phenomenology) and hep-ex (high energy experiment).

    Why read ParticleBites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.

    Our goal is to solve this problem, one paper at a time. With each brief ParticleBite, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in particle physics.

    Who writes ParticleBites?

    ParticleBites is written and edited by graduate students and postdocs working in high energy physics. Feel free to contact us if you’re interested in applying to write for ParticleBites.

    ParticleBites was founded in 2013 by Flip Tanedo following the Communicating Science (ComSciCon) 2013 workshop.

    2
    Flip Tanedo UCI Chancellor’s ADVANCE postdoctoral scholar in theoretical physics. As of July 2016, I will be an assistant professor of physics at the University of California, Riverside

    It is now organized and directed by Flip and Julia Gonski, with ongoing guidance from Nathan Sanders.

     
  • richardmitnick 2:04 pm on December 1, 2019 Permalink | Reply
    Tags: "NA61/SHINE gives neutrino experiments a helping hand", , , , HEP, ,   

    From CERN: “NA61/SHINE gives neutrino experiments a helping hand” 

    Cern New Bloc

    Cern New Particle Event


    From CERN

    How particle measurements made by the NA61/SHINE experiment at CERN are helping neutrino experiments in the US and Japan

    1
    Inside the NA61/SHINE experiment at CERN (Image: CERN)

    Neutrinos are the lightest of all the known particles that have mass. Yet their behaviour as they travel could help answer one of the greatest puzzles in physics: why the present-day universe is made mostly of matter when the Big Bang should have produced equal amounts of matter and antimatter. In two recent papers, the NA61/SHINE collaboration reports particle measurements that are crucial for accelerator-based experiments studying such neutrino behaviour.

    Neutrinos come in three types, or “flavours”, and neutrino experiments are measuring with ever increasing detail how they and their antimatter counterparts, antineutrinos, “oscillate” from one flavour to another while they travel. If it turns out that neutrinos and antineutrinos oscillate in a different way from one another, this may partially account for the present-day matter–antimatter imbalance.

    Accelerator-based neutrino experiments look for neutrino oscillations by producing a beam of neutrinos of one flavour and measuring the beam after it has travelled a long distance. The neutrino beams are typically produced by firing a beam of high-energy protons into long, thin carbon or beryllium targets. These proton–target interactions produce hadrons, such as pions and kaons, which are focused using magnetic aluminium horns and directed into long tunnels, in which they transform into neutrinos and other particles.

    To get a reliable measurement of the neutrino oscillations, the researchers working on these experiments need to estimate the number of neutrinos in the beam before oscillation and how this number varies with the energy of the particles. Estimating this “neutrino flux” is hard, because neutrinos interact very weakly with other particles and cannot be measured easily. To get around this, researchers estimate instead the number of hadrons. But measuring the number of hadrons is also challenging, because there are too many of them to measure precisely.

    This is where experiments such as NA61/SHINE at CERN’s Super Proton Synchrotron come in. NA61/SHINE can reproduce the proton–target interactions that generate the hadrons that transform into neutrinos. It can also reproduce subsequent interactions that protons and hadrons undergo in the targets and focusing horns. These subsequent interactions can produce additional neutrino-yielding hadrons.

    The NA61/SHINE collaboration has previously measured hadrons generated in experiments at 31 GeV/c proton energy (where c is the speed of light) to help predict the neutrino flux in the Tokai-to-Kamioka (T2K) neutrino-oscillation experiment in Japan. The collaboration has also been gathering data at 60 and 120 GeV/c energies to benefit the MINERνA, NOνA and DUNE experiments at Fermilab in the US. The analysis of these datasets is progressing well and has most recently led to two papers: one describing measurements of interactions of protons with carbon, beryllium and aluminium, and another reporting measurements of interactions of pions with carbon and beryllium.

    “These results are crucial for Fermilab’s neutrino experiments,” says Laura Fields, an NA61/SHINE collaboration member and co-spokesperson for MINERνA. “To predict the neutrino fluxes for these experiments, researchers need an extremely detailed simulation of the entire beamline and all of the interactions that happen within it. For that simulation we need to know the probability that each type of interaction will happen, the particles that will be produced, and their properties. So interaction measurements such as the latest ones will be vital to make these simulations much more accurate,” she explains.

    “Looking into the future, NA61/SHINE will focus on measurements for the next generation of neutrino-oscillation experiments, including DUNE and T2HK in Japan, to enable these experiments to produce high-precision results in neutrino physics,” Fields concludes.

    See also this Experimental Physics newsletter article.

    See the full article here.


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    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Tunnel

    CERN LHC particles

     
  • richardmitnick 12:27 pm on November 27, 2019 Permalink | Reply
    Tags: "The plot thickens for a hypothetical “X17” particle", , Additional evidence of an unknown particle from a Hungarian lab, , , HEP, , , ,   

    From CERN: “The plot thickens for a hypothetical “X17” particle” 

    Cern New Bloc

    Cern New Particle Event


    From CERN

    27 November, 2019
    Ana Lopes

    Additional evidence of an unknown particle from a Hungarian lab gives a new impetus to NA64 searches.

    CERN NA64


    The NA64 experiment at CERN (Image: CERN)

    Fresh evidence of an unknown particle that could carry a fifth force of nature gives the NA64 collaboration at CERN a new incentive to continue searches.

    In 2015, a team of scientists spotted [Physical Review Letters] an unexpected glitch, or “anomaly”, in a nuclear transition that could be explained by the production of an unknown particle. About a year later, theorists suggested [Physical Review Letters] that the new particle could be evidence of a new fundamental force of nature, in addition to electromagnetism, gravity and the strong and weak forces. The findings caught worldwide attention and prompted, among other studies, a direct search [Physical Review Letters] for the particle by the NA64 collaboration at CERN.

    A new paper from the same team, led by Attila Krasznahorkay at the Atomki institute in Hungary, now reports another anomaly, in a similar nuclear transition, that could also be explained by the same hypothetical particle.

    The first anomaly spotted by Krasznahorkay’s team was seen in a transition of beryllium-8 nuclei. This transition emits a high-energy virtual photon that transforms into an electron and its antimatter counterpart, a positron. Examining the number of electron–positron pairs at different angles of separation, the researchers found an unexpected surplus of pairs at a separation angle of about 140º. In contrast, theory predicts that the number of pairs decreases with increasing separation angle, with no excess at a particular angle. Krasznahorkay and colleagues reasoned that the excess could be interpreted by the production of a new particle with a mass of about 17 million electronvolts (MeV), the “X17” particle, which would transform into an electron–positron pair.

    The latest anomaly reported by Krasznahorkay’s team, in a paper [.pdf above] that has yet to be peer-reviewed, is also in the form of an excess of electron–positron pairs, but this time the excess is from a transition of helium-4 nuclei. “In this case, the excess occurs at an angle 115º but it can also be interpreted by the production of a particle with a mass of about 17 MeV,” explained Krasznahorkay. “The result lends support to our previous result and the possible existence of a new elementary particle,” he adds.

    Sergei Gninenko, spokesperson for the NA64 collaboration at CERN, which has not found signs of X17 in its direct search, says: “The Atomki anomalies could be due to an experimental effect, a nuclear physics effect or something completely new such as a new particle. To test the hypothesis that they are caused by a new particle, both a detailed theoretical analysis of the compatibility between the beryllium-8 and the helium-4 results as well as independent experimental confirmation is crucial.”

    The NA64 collaboration searches for X17 by firing a beam of tens of billions of electrons from the Super Proton Synchrotron accelerator onto a fixed target.

    The Super Proton Synchrotron (SPS), CERN’s second-largest accelerator

    If X17 did exist, the interactions between the electrons and nuclei in the target would sometimes produce this particle, which would then transform into an electron–positron pair. The collaboration has so far found no indication that such events took place, but its datasets allowed them to exclude part of the possible values for the strength of the interaction between X17 and an electron. The team is now upgrading their detector for the next round of searches, which are expected to be more challenging but at the same time more exciting, says Gninenko.

    Among other experiments that could also hunt for X17 in direct searches are the LHCb experiment and the recently approved FASER experiment, both at CERN.

    CERN/LHCb detector

    CERN FASER experiment schematic

    Jesse Thaler, a theoretical physicist from the Massachusetts Institute of Technology, says: “By 2023, the LHCb experiment should be able to make a definitive measurement to confirm or refute the interpretation of the Atomki anomalies as arising from a new fundamental force. In the meantime, experiments such as NA64 can continue to chip away at the possible values for the hypothetical particle’s properties, and every new analysis brings with it the possibility (however remote) of discovery.”

    See the full article here.


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    Please help promote STEM in your local schools.

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    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Tunnel

    CERN LHC particles

     
  • richardmitnick 4:10 pm on November 14, 2019 Permalink | Reply
    Tags: , , , , HEP, , ,   

    From Fermi National Accelerator Lab: “Discovery of a new type of particle beam instability” 

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

    November 14, 2019
    Alexey Burov

    Accelerated, charged particle beams do what light does for microscopes: illuminate matter. The more intense the beams, the more easily scientists can examine the object they are looking at. But intensity comes with a cost: the more intense the beams, the more they become prone to instabilities.

    One type of instability occurs when the average energy of accelerated particles traveling through a circular machine reaches its transition value. The transition point occurs when the particles revolve around the ring at the same rate, even though they do not all carry the same energy — in fact, they exhibit a range of energies. The specific motion of the particles near the transition energy makes them extremely prone to collective instabilities.

    These particular instabilities were observed for decades, but they were not sufficiently understood. In fact, they were misinterpreted. In a paper published this year, I suggest a new theory about these instabilities. The application of this theory to the Fermilab Booster accelerator predicted the main features of the instability there at the transition crossing, suggesting better ways to suppress the instability. Recent measurements confirmed the predictions, and more detailed experimental beam studies are planned in the near future.

    1
    Recent measurements at the Fermilab Booster accelerator confirmed existence of a certain kind of particle beam instability. More measurements are planned for the near future to examine new methods proposed to mitigate it.

    Accelerating high-intensity beams is a crucial part of the Fermilab scientific program. A solid theoretical understanding of particle beam behavior equips experimentalists to better manipulate the accelerator parameters to suppress instability. This leads to the high-intensity beams needed for Fermilab’s experiments in fundamental physics. It is also useful for any experiment or institution operating circular accelerators.

    Beam protons talk to each other by electromagnetic fields, which are of two kinds. One is called the Coulomb field. These fields are local and, by themselves, cannot drive instabilities. The second kind is the wake field. Wake fields are radiated by the particles and trail behind them, sometimes far behind.

    When a particle strays from the beam path, the wake field translates this departure backward — in the wake left by the particle. Even a small departure from the path may not escape being carried backward by these electromagnetic fields. If the beams are intense enough, their wakes can destabilize them.

    In the new theory, I suggested a compact mathematical model that effectively takes both sorts of fields into account, realizing that both of them are important when they are strong enough, as they typically are near transition energy.

    This kind of huge amplification happens at CERN’s Proton Synchrotron, for example, as I showed in my more recent paper, submitted to Physical Review Accelerators and Beams. If not suppressed one way or another, this amplification may grow until the beam touches the vacuum chamber wall and becomes lost. Recent measurements at the Fermilab Booster confirmed existence of a similar instability there; more measurements are planned for the near future to examine new methods proposed to mitigate it.

    These phenomena are called transverse convective instabilities, and the discoveries of how they arise open new doors to theoretical, numerical and experimental ways to better understanding and better dealing with the intense proton beams.

    This work is supported by the DOE Office of Science.

    Science paper:
    Convective instabilities of bunched beams with space charge
    Physical Review Accelerators and Beams

    See the full here.


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    Please help promote STEM in your local schools.

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    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 2:25 pm on November 11, 2019 Permalink | Reply
    Tags: "LHCf gears up to probe birth of cosmic-ray showers", , , HEP, , ,   

    From CERN: “LHCf gears up to probe birth of cosmic-ray showers” 

    Cern New Bloc

    Cern New Particle Event


    From CERN

    11 November, 2019
    Ana Lopes


    CERN LHCf

    1
    One of the LHCf experiment’s two detectors, LHCf Arm2, seen here during installation into a particle absorber that surrounds the LHC’s beam pipe. (Image: Lorenzo Bonechi)

    Cosmic rays are particles from outer space, typically protons, travelling at almost the speed of light. When the most energetic of these particles strike the atmosphere of our planet, they interact with atomic nuclei in the atmosphere and produce cascades of secondary particles that shower down to the Earth’s surface. These extensive air showers, as they are known, are similar to the cascades of particles that are created in collisions inside particle colliders such as CERN’s Large Hadron Collider (LHC). In the next LHC, run starting in 2021, the smallest of the LHC experiments – the LHCf experiment – is set to probe the first interaction that triggers these cosmic showers.

    Observations of extensive air showers are generally interpreted using computer simulations that involve a model of how cosmic rays interact with atomic nuclei in the atmosphere. But different models exist and it’s unclear which one is the most appropriate. The LHCf experiment is in an ideal position to test these models and help shed light on cosmic-ray interactions.

    In contrast to the main LHC experiments, which measure particles emitted at large angles from the collision line, the LHCf experiment measures particles that fly out in the “forward” direction, that is, at small angles from the collision line. These particles, which carry a large portion of the collision energy, can be used to probe the small angles and high energies at which the predictions from the different models don’t match.

    Using data from proton–proton LHC collisions at an energy of 13 TeV, LHCf has recently measured how the number of forward photons and neutrons varies with particle energy at previously unexplored high energies. These measurements agree better with some models than others, and they are being factored in by modellers of extensive air showers.

    In the next LHC run, LHCf should extend the range of particle energies probed, due to the planned higher collision energy. In addition, and thanks to ongoing upgrade work, the experiment should also increase the number and type of particles that are detected and studied.

    What’s more, the experiment plans to measure forward particles emitted from collisions of protons with light ions, most likely oxygen ions. The first interactions that trigger extensive air showers in the atmosphere involve mainly light atomic nuclei such as oxygen and nitrogen. LHCf could therefore probe such an interaction in the next run, casting new light on cosmic-ray interaction models at high energies.

    Find out more in the Experimental Physics newsletter article.

    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 in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Tunnel

    CERN LHC particles

     
  • richardmitnick 2:23 pm on November 6, 2019 Permalink | Reply
    Tags: , , CERN Council selected Fabiola Gianotti as the Organization’s next Director-General for her second term of office., HEP, , ,   

    From CERN: “CERN Council appoints Fabiola Gianotti for second term of office as CERN Director General” 

    Cern New Bloc

    Cern New Particle Event


    From CERN

    6 November, 2019

    At its 195th Session today, the CERN Council selected Fabiola Gianotti, as the Organization’s next Director-General, for her second term of office.

    1
    President of the CERN Council, Ursula Bassler and Director-General of CERN, Fabiola Gianotti (Image: CERN)

    At its 195th Session today, the CERN Council selected Fabiola Gianotti, as the Organization’s next Director-General, for her second term of office. The appointment will be formalised at the December Session of the Council, and Gianotti’s new five-year term of office will begin on 1 January 2021. This is the first time in CERN’s history that a Director-General has been appointed for a full second term.

    “I congratulate Fabiola Gianotti very warmly for her reappointment as Director-General for another five-year term of office. With her at the helm, CERN will continue to benefit from her strong leadership and experience, especially for important upcoming projects such as the High-Luminosity LHC, implementation of the European Strategy for Particle Physics, and the construction of the Science Gateway,” said President of the CERN Council, Ursula Bassler. “During her first term, she excelled in leading our diverse and international scientific organisation, becoming a role model, especially for women in science”.

    “I am deeply grateful to the CERN Council for their renewed trust. It is a great privilege and a huge responsibility,” said CERN Director-General, Fabiola Gianotti. “The following years will be crucial for laying the foundations of CERN’s future projects and I am honoured to have the opportunity to work with the CERN Member States, Associate Member States, other international partners and the worldwide particle physics community.”

    Gianotti has been CERN’s Director-General since 1 January 2016. She received her Ph.D. in experimental particle physics from the University of Milano in 1989 and has been a research physicist at CERN since 1994. She was the leader of the ATLAS experiment’s collaboration from March 2009 to February 2013, including the period in which the LHC experiments ATLAS and CMS announced the discovery of the Higgs boson. The discovery was recognised in 2013 with the Nobel Prize in Physics being awarded to theorists François Englert and Peter Higgs. Gianotti is a member of many international committees, and has received numerous prestigious awards. She was the first woman to become the Director-General of CERN.

    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 in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Tunnel

    CERN LHC particles

     
  • richardmitnick 12:47 pm on November 5, 2019 Permalink | Reply
    Tags: "Put it to the test beam", , , HEP, , , ,   

    From Symmetry: “Put it to the test beam” 

    Symmetry Mag
    From Symmetry<

    11/05/19
    Lauren Biron

    Before a detector component can head to its forever home, it has to pass the test.

    1
    Photo by Reidar Hahn, Fermilab

    If building a modern particle physics experiment is a marathon, then visiting a test beam facility is the 100-meter dash. Over the course of just a few weeks, small teams work non-stop to gather as much data as they can about a piece of equipment they are thinking of installing in an experiment.

    “It is stressful, but I think it’s super fun,” says Jessica Metcalfe, a researcher at Argonne working on upgrades for the innermost part of the ATLAS detector, one of the two major detectors at CERN that co-discovered the Higgs boson.

    CERN ATLAS Credit CERN SCIENCE PHOTO LIBRARY

    “You’re all there squeezed together in the tiny control room, problem solving, all very focused on a very specific goal, and you learn a lot—really fast.”

    Test beams generally sit to the side of full-on accelerators, sipping beam and passing it to the reconfigurable spaces housing temporary experiments. Scientists bring pieces of their detectors—sensors, chips, electronics or other material—and blast them with the well understood beam to see if things work how they expect, and if their software performs as expected. If things check out, they’re one step closer to being installed in a detector, and if not, it’s a chance to do some R&D, tinker and make things work.

    “We’re typically testing pieces that are going into a larger experiment, but you’re also doing research on the detector technology, which is a form of research in itself,” Metcalfe says. “We’re not just getting ready to build something, we’re also learning a lot about the devices. There’s often many iterations of design and redevelopment.”

    Test beam visits are typically short, and getting time can be competitive because there are only a handful of places around the world that have high-energy particle beams available for testing. When it comes to hadrons—particles made of quarks—there are really just two: the Department of Energy’s Fermilab in the United States and CERN in Europe.

    Other test beams specialize in different particles, for example, electrons (at Germany’s DESY or California’s SLAC National Accelerator Laboratory) and photons (like at the Research Center for Electron Photon Science in Japan).

    3

    “It’s part of the lifecycle of any detector you build,” says Mandy Rominsky, who manages the Fermilab Test Beam Facility. “You start on a bench with an idea, and before you put something into a running experiment, you always put it in a test beam. You need to be able to characterize it, change it and go back and forth—and you can’t do that on a bench.”

    Groups come with components of all shapes and sizes to the test beam. At the Fermilab test beam alone, researchers have tested teeny, tiny pieces of scintillator (the material that captures particles of light) and detector panels taller than people. Researchers come from many scientific fields, including nuclear physics, neutrino physics, collider physics, dark matter physics and astronomy. There are people working on general research and development without a specific experiment in mind, and ultra-specific tasks, like the crew working on turning smartphones into cosmic ray detectors. Still others are interested in learning how the materials they plan to put in a detector will change over time, especially in the harsh environment surrounding particle collisions.

    Test-beam facilities try to keep useful experimental infrastructure on hand for visiting researchers: There are movable tables to pull equipment in and out, cooling systems and electronics, cables, different kinds of gas, cranes, and, of course, the beam itself, which often comes in many flavors of particles and energies. But some experiments need to bring in a little something extra, creating odd requests for facility managers—like when a visiting group from the IceCube experiment needed about 1000 gallons of deionized water to test their modules before similar detectors were shipped to the South Pole and entombed in the ice.

    “It is surprisingly difficult to get that much deionized water,” Rominsky notes. “We couldn’t use a tanker and had to ship it in from Indiana in 55-gallon drums.”

    And while most components will have only a short stay in the test beam, some facilities do have areas for longer-term experiments. For example, the LArIAT (Liquid Argon in a Test beam) detector lived its full existence in the test beam, collecting data for three years at Fermilab.

    6

    Its goal was to better understand how particles interact with argon, the material now being used in massive neutrino detectors such as MicroBooNE and the international Deep Underground Neutrino Experiment hosted by Fermilab.

    FNAL/MicrobooNE

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    “I like that we help everybody,” Rominsky says. “It doesn’t matter which groups come to us. Our policy is to be very helpful to everyone.”

    7
    IceCube PMT beam test at Fermilab Test Beam Facility. Photo by Reidar Hahn, Fermilab.

    8
    Meson Test Beam Facility with LArIAT Detector. Photo by Reidar Hahn, Fermilab

    Research crucible

    Test beams are not only important for detectors themselves—the test beam experience is also formative for the researchers who come to do the hands-on work. Teams work together over long hours, sharing both shifts and meals, ups and downs.

    “For me, it was really communal,” says Clara Nellist, an ATLAS researcher at Radboud University in the Netherlands and former co-organizer of the annual Beam Telescope and Test Beams Workshop. “I learned so much from other people, even though we were from different universities and, in essence, we were competing.”

    Nellist did her PhD thesis on proposed technology for the ATLAS pixel detector and spent many night shifts at the CERN test beam facility. Sometimes, groups working on a different proposed sensor intended for the same slot in the detector would share the same experimental setup. When the competing team didn’t have enough people to run their shifts, she volunteered to take data for them. A few months later, she unexpectedly found herself on their research paper for contributing to their data.

    “We needed each other’s expertise,” Nellist says. “There are friends I made in the first week of my PhD who, 10 years later, I’m still friends with and check up on.”

    The diverse nature of projects also means researchers from all different stages of their careers make their way through the test beam facility doors.

    “You get people who are legends in the detector R&D community, and they need beam time like everyone else, and then there are undergrads having their first lab experience,” explains Aria Soha, an engineering physicist at Fermilab who managed the test beam facility until 2013. For those new to hardware testing—and even the more seasoned pros—it’s a thrill to watch those first particle tracks splash across the detector.

    “I remember knowing when the beam was coming and watching the particles show up, and thinking, ‘This is cool, this is why I went to school for physics,’” Soha says.

    Those moments of triumph often come after a stressful period of testing and debugging.

    “You test everything in the lab before you go. Everything works perfectly and then you go [to the test beam] and nothing works,” Metcalfe says. “Checking the cables and turning things on and off solves about 80% of the problems.”

    The granular, hands-on experience can make a big difference in understanding the results coming out of the detector later on. Visiting a test beam teaches researchers how particles are going through their detector, how they interact, how the data looks when it comes out, and much more. If researchers see a problem in their data analysis, they can recognize the potential causes more quickly, Metcalfe says. These are skills for the future of physics.

    “There’s going to be a next generation of experiments, and people need to know how to design them and how to make that design motivated by the physics you want to do,” Metcalfe says. “It’s part of the training.”

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
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