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  • richardmitnick 2:47 pm on June 8, 2016 Permalink | Reply
    Tags: , , FNAL FAST, New beginning at FAST: Research accelerator reaches design beam energy   

    From FNAL: “New beginning at FAST: Research accelerator reaches design beam energy” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    June 8, 2016
    Leah Hesla

    1
    Fermilab accelerator scientist Jinhao Ruan (center) shows Fermilab Director Nigel Lockyer (left) the laser setup for the FAST photoinjector. Vladimir Shiltsev (right) is director of the Fermilab Accelerator Physics Center. Photo: Reidar Hahn

    On May 16, Fermilab sent an electron beam with an energy of 50 million electronvolts, or MeV, through the photoinjector at the Fermilab Accelerator Science and Technology facility (FAST), achieving a major design goal for the accelerator – and marking the beginning of a new accelerator science program at the laboratory.

    1
    FNAL FAST

    “This is a major milestone for our general accelerator R&D,” said Vladimir Shiltsev, head of the Fermilab Accelerator Physics Center. “The delivery of this beam marks the start of a new program here – new facility, new science capabilities,” Shiltsev said.

    The delivery of 50-MeV beam is the first step in establishing an accelerator R&D facility that will serve as one of America’s leading test beds for cutting-edge, record-high-intensity particle beam research. Once complete, FAST will provide scientists and engineers from around the world with a place to study the science of high-intensity particle beams and superconducting radio-frequency acceleration, the technology on which nearly all future high-energy accelerators are based.

    The photoinjector is just the first phase of a larger accelerator to be built at FAST, which is supported by the DOE Office of Science. It will include a superconducting linear accelerator and a particle storage ring called the Integrable Optics Test Accelerator, or IOTA, which will be built over the next two years.

    Although the photoinjector is just the front section of what will become a higher-energy accelerator, it still provides enough beam to be useful for carrying out scientific research. In fact, the first accelerator physics researchers to sign up for time at the facility have now begun using the electron beam. The inaugural group, led by Northern Illinois University professors Philippe Piot and Swapan Chattopadhyay, has reserved two months of beam time as part of the Fermilab-NIU Research Cluster.

    For FAST to produce the kinds of beams that are useful for accelerator R&D, its initial electron beam had to have an energy of 50 MeV. In 2015, Fermilab delivered a 20-MeV electron beam. Since then, scientists, engineers and technicians have upgraded the photoinjector to meet specifications, including installing a refurbished accelerating cavity that had been used elsewhere on the Fermilab site.

    “It takes a significant effort to install all the complex components and subsystems that make up such an accelerator, and everything has to be done just right,” said Jerry Leibfritz, project engineer for FAST. “The fact that both 20-MeV and 50-MeV beams were achieved within a day or two of the start of commissioning is truly a testament to the excellent work and dedication of all those involved in this project.”

    In the current setup, electron bunches generated by a laser are accelerated through two superconducting accelerating cavities (including the refurbished cavity), which bring the energy of electrons to 50 MeV.

    As work on FAST progresses, the electron beam will continue through another eight superconducting radio-frequency cavities, accelerating to 300 MeV before entering the beamline for IOTA.

    “FAST represents the beginning of a new era at Fermilab, in which the study and development of high-intensity particle beams become an important and productive part of the laboratory program,” said Fermilab Director Nigel Lockyer.

    See the full article here .

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    Fermilab Campus

    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.

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  • richardmitnick 9:43 am on June 6, 2016 Permalink | Reply
    Tags: , , , , ,   

    From FNAL: “Exclusive production: shedding light with grazing protons” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    June 3, 2016
    Bo Jayatilaka

    1
    When two protons approaching each other pass close enough together, they can “feel” each other, similar to the way that two magnets can be drawn closely together without necessarily sticking together. According to the Standard Model, at this grazing distance, the protons can produce a pair of W bosons. No image credit.

    As its name implies, the primary mission of the Large Hadron Collider is to generate collisions of protons for study by physicists at experiments such as CMS.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    CERN/CMS Detector
    CERN/CMS Detector

    It may surprise you to find out that the vast majority of protons accelerated by the LHC never collide with one another. Some of these fly-by protons, however, still interact with each other in such a way as to help physicists shed light on the nature of the universe.

    The LHC accelerates bunches of protons, with more than 10 billion protons in each bunch, in opposite directions around the ring. As those protons arrive at a detector, such as CMS, magnets focus the beams to increase the density of protons and thus increase the chance of a coveted collision. Despite what seems like overwhelming odds, only a few of these protons actually collide with each other: tens to hundreds per each beam “crossing.” An even smaller fraction of the remaining protons pass close enough to other protons to “feel” each other, even if they do not directly collide.

    Think of two toy magnets on a tabletop: A north end and a south end moved close enough to each other will rather firmly stick to each other. However, you can also move one magnet just close enough to the other that you can make it wiggle without drawing it all the way over. This exchange of energy is mediated by the exchange of photons, the carrier particle of the electromagnetic force. Similarly, two protons in the LHC that get just the right distance from each other will exchange photons without colliding.

    Now for the part that gets really interesting to particle physicists. The photons generated by these near-miss proton interactions can be billions of times more energetic than those of visible light, and as a result they carry enough energy to create particles in their own right. The Standard Model predicts the production of massive particles, such as pairs of W bosons, from these interacting photons without any of the additional activity that is seen in the messier proton-proton collision events.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    In a detector such as CMS, this pair of W bosons is said to be produced “exclusively.” However, “exclusive production” is an apt name in another way – creating a pair of W bosons from interacting photons is a rare occurrence in an even rarer sample of photons generated from near-miss proton interactions.

    CMS scientists performed such a search for such W boson pairs emanating from interacting photons. In a data set consisting of 7- and 8-TeV collisions, 15 candidate events for this process were observed. While it may not seem like much, the expected background was considerably smaller, allowing the CMS team to claim that they have evidence of the process. (In the particle physics world, evidence is a three-standard-deviation departure from background, as explained here). Furthermore, these results helped place stringent results on a number of models which predict a greater rate of this process.

    See the full article here .

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    Fermilab Campus

    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 10:31 am on June 3, 2016 Permalink | Reply
    Tags: AIDA, , , ,   

    From AIDA: “AIDA-2020: First Year in Review” 

    AIDA 2020 bloc

    Advanced European Infrastructures for Detectors at Accelerators

    27/05/2016
    Laurent Serin (CNRS)

    1
    Group photo of project members attending the AIDA-2020 Kick-off meeting at CERN, June 2015 (Image: CERN)

    2
    CMS Pixel Detector, Image credit: CMS

    3
    View of the ATLAS calorimeters from below

    DESY/FLASH
    DESY/FLASH

    European XFEL Test module
    European XFEL Test module

    Following the success of the AIDA project, AIDA-2020 started one year ago in May 2015. The project groups a large fraction of the High Energy Physics R&D community in Europe, united in the goal of advancing detector technology and infrastructures for the future. The community represents most forms of detector technology and is very active in its work and networking.

    On Track is to serve as a newsletter for the AIDA-2020 project as well as the wider detector community. Its launch will allow the detector community at large to exchange information and results by highlighting new developments in the field and serving as an active source of news.

    Over its first year, the irradiation and test beam facilities supported by the Transnational Access programme were already going full speed. In addition, new facilities such as the micro beam at RBI in Croatia and the electromagnetic compatibility testing facility at ITAINNOVA in Spain had some of their first users under this programme. There are also ongoing improvements of tracking devices at DESY and CERN or upgraded irradiations facilities at CERN and JSI.

    There has been progress on each detector technology (pixels, calorimeter and gas detector) with qualification measurements, and beam tests are expected to be conducted over summer 2016, as well as dedicated meetings and tutorials on TCAD simulations.

    Silicon detectors used for energy and time measurements are among the new ways investigated by the collider experiments (CMS, ATLAS, CALICE). A dedicated workshop will be organized by AIDA-2020 on June 13th at DESY, during the first annual meeting, to initiate cross-experiment interactions between these key actors.

    I look forward to the first annual meeting at DESY (Hamburg, Germany) where we will be able to discuss the first year results and the activities of the coming year. After having managed AIDA and this first year of AIDA-2020 running well, it is also time for me to pass the baton to Felix Sefkow as the AIDA-2020 Scientific Coordinator. Felix will impulse new ideas for the project, and open it further to detector applications outside our field, guiding AIDA-2020 to new ventures in the years ahead.

    See the full article here .

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    What is AIDA-2020?

    The AIDA-2020 project brings together the leading European research infrastructures in the field of detector development and testing and a number of institutes, universities and technological centers, thus assembling the necessary expertise for the ambitious programme of work.
    Who is involved?

    In total, 24 countries and CERN are involved in a coherent and coordinated programme of NAs, TAs and JRAs, fully in line with the priorities of the European Strategy for Particle Physics.
    What benefits does AIDA-2020 offer?

    AIDA-2020 aims to advance detector technologies beyond current limits by offering well-equipped test beam and irradiation facilities for testing detector systems under its Transnational Access programme. Common software tools, micro-electronics and data acquisition systems are also provided. This shared high-quality infrastructure will ensure optimal use and coherent development, thus increasing knowledge exchange between European groups and maximising scientific progress. The project also exploits the innovation potential of detector research by engaging with European industry for large-scale production of detector systems and by developing applications outside of particle physics, e.g. for medical imaging.

    AIDA-2020 will lead to enhanced coordination within the European detector community, leveraging EU and national resources. The project will explore novel detector technologies and will provide the ERA with world-class infrastructure for detector development, benefiting thousands of researchers participating in future particle physics projects, and contributing to maintaining Europe’s leadership of the field.

     
  • richardmitnick 3:34 pm on May 22, 2016 Permalink | Reply
    Tags: , , , , , ,   

    From HuffPost: “Meet The Most Powerful Woman In Particle Physics” Women in Science 

    Huffington Post
    The Huffington Post

    05/18/2016
    David Freeman

    1
    Fabiola Gianotti, CERN’s new director-general. Christian Beutler

    Fabiola Gianotti isn’t new to CERN, the Geneva, Switzerland-based research organization that operates the Large Hadron Collider (LHC), the world’s biggest particle collider.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    In fact, the Italian particle physicist was among the CERN scientists who made history in 2012 with the discovery of the Higgs boson.

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    CERN/CMS Detector
    CERN/CMS Detector

    But now Gianotti isn’t just working at CERN. As the organization’s new director-general — the first woman ever to hold the position — she’s running the show. And though expanding our knowledge of the subatomic realm remains her main focus, she’s acutely aware that she is now a high-visibility role model for women around the world.

    “Physics is widely regarding as a male-dominated field, and it’s true that there are more men in our community than women,” Gianotti told The Huffington Post in an email. “So I am glad if in my new role I can contribute to encourage young women to undertake a job in scientific research with the certitude that they have the same opportunities as men.”

    Recently, HuffPost Science posed a few questions to Gianotti via email. Here, lightly edited, are her answers.

    How will things be different for you in your new role?

    My new role is very interesting and stimulating, and I feel very honored to have been offered it. The range of issues I have to deal with is much broader than before and includes scientific strategy and planning, budget, personnel aspects, relations with a large variety of stakeholders, etc. Days are long and full, and I am learning many new things. And there is nothing more enriching and gratifying than learning.

    What’s a typical day like for you?

    Super-hectic, super-speedy and … atypical!

    What do you think explains the gender gap in science generally and in physics particularly?

    There are many factors. There’s no difference in ability between men and women, that’s for sure. And in my experience, the more diverse a team is, the stronger it is. There is the baggage of history, of course, which takes a long time to overcome. There is the question of the lack of role models, and there is the question of making workplaces more family friendly. We need to enable parents, men or women, to take breaks to raise families and we need to support parents with infrastructure and facilities.

    2
    The Large Hadron Collider, Geneva, Switzerland.

    Your term as CERN’s director-general is scheduled to last five years. What are your goals for CERN during this period?

    The second run of the LHC is the top priority for CERN in the coming years. We got off to a very good start in 2015, and have three years of data-taking ahead of us before we go into the accelerator’s second long shutdown. The experiments are expected to record at least three times more data than in Run 1 at an energy almost twice as large. It will be a long time before another such step in energy will be made in the future.

    So, the coming years are going to be an exciting period for high-energy physics. But CERN is not just the LHC. We have a variety of experiments and facilities, including precise measurements of rare decays and detailed studies of antimatter, to mention just a couple of them. In parallel with the ongoing program, we will be working to ensure a healthy long-term future for CERN, at first with the high-luminosity LHC upgrade scheduled to come on stream in the middle of the next decade, and also through a range of design studies looking at the post-LHC era — from 2035 onwards.

    CERN HL-LHC bloc

    What discoveries can we reasonably expect from CERN during your term?

    I’m afraid that I don’t have a crystal ball to hand. There will be a wealth of excellent physics results from the LHC Run 2 and from other CERN experiments. We’ll certainly get to know the Higgs boson much better and expand our exploration of physics beyond the Standard Model.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Whether we find any hints of the new physics everyone is so eagerly waiting for, however, I don’t know. We know there’s new physics to be found. Good as it is, the Standard Model explains only the 5 percent of the universe that is visible. There are so many exciting questions still waiting to be answered.

    What are the biggest opportunities at CERN? The biggest challenges?

    These two questions have a single answer. Over the coming years, the greatest opportunities and challenges, not only for CERN but for the global particle physics community as a whole, come from the changing nature of the field. Collaboration between regions is growing. CERN recently signed a set of agreements with the U.S. outlining U.S. participation in the upgrade of the LHC and CERN participation in neutrino projects at Fermilab in the U.S.

    FNAL LBNF/DUNE
    FNAL LBNF/DUNE

    There are also emerging players in the field, notably China, whose scientific community has expressed ambitious goals for a potential future facility. All this represents a great opportunity for particle physics. The challenge for all of us in the field is to advance in a globally coordinated manner, so as to be able to carry out as many exciting and complementary projects as possible.

    Were you always interested in being a scientist? If you couldn’t be a scientist, what would you be/do?

    I was always interested in science, and I was always interested in music. I pursued both for as long as I could, but when the time came to make a choice, I chose science. I suppose that as a professional physicist, it is still possible to enjoy music — I still play the piano from time to time. But as a professional musician, it would be harder to engage in science.

    What do you do in your spare time?

    I spend my little spare time with family and friends. I do some sport, I listen to music, I read.

    What do you think is the biggest misconception nonscientists have about particle physics?

    That it’s hard to understand! Of course, if you want to be a particle physicist, you have to master the language of mathematics and be trained to quite a high level. But if you want to understand the field conceptually, it’s almost child’s play. All children are natural scientists. They are curious, and they want to take things apart to see how they work.

    Particle physics is just like that. We study the fundamental building blocks of matter from which everything is made, and the forces at work between them. And the equations that describe the building blocks and their interactions are simple and elegant. They can be written on a small piece of paper.

    See the full article here .

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  • richardmitnick 8:28 am on May 22, 2016 Permalink | Reply
    Tags: , , , , , ,   

    From livescience: “LHC [Particle] Smasher Opens Quantum Physics Floodgates” 

    Livescience

    May 20, 2016
    Ian O’Neill, Discovery News

    1
    A display of a proton-proton collision taken in the LHCb detector in the early hours of May 9.
    Credit: CERN/LHCB

    CERN/LHCb
    CERN/LHCb

    A display of a proton-proton collision taken in the LHCb detector in the early hours of May 9. Credit: CERN/LHCb

    The Large Hadron Collider is the most complex machine ever built by humankind and it is probing into deep quantum unknown, revealing never-before-seen detail in the matter and forces that underpin the foundations of our universe.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    In its most basic sense, the LHC is a time machine; with each relativistic proton-on-proton collision, the particle accelerator is revealing energy densities and states of matter that haven’t existed in our universe since the moment after the Big Bang, nearly 14 billion years ago.

    The collider, which is managed by the European Organization for Nuclear Research (CERN) is located near Geneva, Switzerland.

    With the countless billions of collisions between ions inside the LHC’s detectors comes a firehose of data that needs to be recorded, deciphered and stored. Since the 27 kilometer (17 mile) circumference ring of supercooled electromagnets started smashing protons together once more after its winter break, LHC scientists are expecting a lot more data this year than what the experiment produced in 2015.

    “The LHC is running extremely well,” said CERN Director for Accelerators and Technology Frédérick Bordry in a statement. “We now have an ambitious goal for 2016, as we plan to deliver around six times more data than in 2015.”

    And this data will contain ever more detailed information about the elusive Higgs boson that was discovered in 2012 and possibly even details of “new” or “exotic” physics that physicists could spend decades trying to understand. Key to the LHC’s aims is to attempt to understand what dark matter is and why the universe is composed of matter and not antimatter.

    In fact, there was already a buzz surrounding an unexpected signal that was recorded in 2015 that could represent something amazing, but as is the mantra of any scientist: more data is needed. And it looks like LHC physicists are about to be flooded with the stuff.

    Central to the LHC’s recent upgrades is the sheer density of accelerated “beams” of protons that are accelerated to close to the speed of light. The more concentrated or focused the beams, the more collisions can be achieved. More collisions means more data and the more likelihood of revealing new and exciting things about our universe. This year, LHC engineers hope to magnetically squeeze the beams of protons when they collide inside the detectors, generating up to one billion proton collisions per second.

    Add these advances in extreme beam control with the fact the LHC will be running at a record-breaking collision energy of 13 TeV and we have the unprecedented opportunity to make some groundbreaking discoveries.

    “In 2015, we opened the doors to a completely new landscape with unprecedented energy. Now we can begin to explore this landscape in depth,” said CERN Director for Research and Computing, Eckhard Elsen.

    The current plan is to continue proton-proton collisions for six months and then carry out a four-week run using much heavier lead ions.

    So the message is clear: Hold onto your hats. We’re in for an incredible year of discovery that could confirm or deny certain models of our universe and revel something completely unexpected and, possibly, something very exotic.

    See the full article here .

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  • richardmitnick 11:07 am on May 19, 2016 Permalink | Reply
    Tags: , , , , The Biggest Hopes Of What A New Particle At The LHC Might Reveal   

    From Ethan Siegel: “The Biggest Hopes Of What A New Particle At The LHC Might Reveal” 

    Starts with a Bang

    May 18, 2016
    Ethan Siegel

    1
    Inside the magnet upgrades on the LHC, that have it running at nearly double the energies of the first (2010-2013) run. Image credit: Richard Juilliart/AFP/Getty Images.

    Built over an 11-year period from 1998 to 2008, the Large Hadron Collider was designed with one goal in mind: to create the greatest numbers of the highest-energy collisions ever, in the hopes of finding new fundamental particles and of revealing new secrets of nature.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    Over a three year period from 2010 to 2013, the LHC collided protons together at energies nearly four times the previous record, with an upgrade nearly doubling that in 2015: to a record 13 TeV, or approximately 14,000 times the energy inherent to a proton via Einstein’s E = mc^2. The largest, most advanced detectors of all — CMS and ATLAS — were built around the main two collision points, collecting as precise and accurate data about all the debris that emerges each time two protons smash together.

    CERN/CMS Detector
    CERN/CMS detector

    CERN/ATLAS detector
    CERN/ATLAS detector

    July 2012 was a watershed moment for particle physics, as enough high-energy collisions were reconstructed to definitively announce, in both detectors, the first concrete, direct evidence for the Higgs Boson: the last undiscovered particle in the Standard Model of particle physics.

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth

    3
    Image credit: The CMS Collaboration, “Observation of the diphoton decay of the Higgs boson and measurement of its properties”, (2014). This was the first “5-sigma” detection of the Higgs.

    But that was expected. The problem is, there are a whole host of questions about the Universe that the Standard Model of particle physics doesn’t answer at a fundamental level, including:

    Why is there more matter than antimatter in the Universe?
    What is dark matter, and what particle(s) beyond the Standard Model (which cannot account for it) explains it?
    Why does our Universe have dark energy, and what is its nature?
    Why don’t the strong interactions in the Standard Model exhibit CP-violation in the strong decays?

    Why do neutrinos have such small but non-zero masses compared to all the other particles?
    And why do the Standard Model particles have the properties and masses that they do, and not any others?

    And the great hope of the LHC, the real hope, is that we’ll learn something extra, beyond the Standard Model, that helps answer one or more of these questions.

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    The particles of the Standard Model, all of which have been detected. Image credit: E. Siegel, from his new book, Beyond The Galaxy.

    With the possible exception of dark energy, all of these problems pretty much require new fundamental particles to explain them. And many of them — the dark matter problem, the matter/antimatter problem, and the mass-of-the-particles problem (a.k.a. the Hierarchy problem) — may actually be within reach at the LHC. One way to look for this new physics is to look for deviations from the expected (and well-calculated) behavior in the decays and other properties of the known, detectable Standard Model particles. So far, to the best of our abilities, everything falls within the “normal” range, where things are perfectly consistent with the Standard Model.

    6
    Image credit: The ATLAS collaboration, 2015, of the various decay channels of the Higgs. The parameter mu = 1 corresponds to a Standard Model Higgs only. Via https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2015-007/.

    But the second way is even better: to discover, directly, evidence for a new particle beyond the Standard Model. As the LHC begins collecting even higher-energy data and with even greater numbers of collisions-per-second, it’s in the best position it’s ever going to be to find new fundamental particles; particles it never expected to find. Of course, it doesn’t exactly find particles; it finds the decay products of particles! Fortunately, because of how physics works, we can reconstruct what energy (and hence, what mass) those particles were created at, and whether we’ve got a new particle after all. At the end of the LHC’s initial run, there’s an intriguing (but not certain) hint of what might be a new particle. This “750 GeV diphoton bump” might not be real, but if it is, it could mean the world to physicists everywhere.

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    The ATLAS and CMS diphoton bumps, displayed together, clearly correlating at ~750 GeV. Image credit: CERN, CMS/ATLAS collaborations, image generated by Matt Strassler at https://profmattstrassler.com/2015/12/16/is-this-the-beginning-of-the-end-of-the-standard-model/.

    The preliminary signal is discernible in both the CMS and the ATLAS detectors so far, and that makes the possibility extra tantalizing. Within about 6 more months, we should know whether this signal is strengthening — and hence likely real — or whether it shows itself to be spurious. If it’s real, here are some of the top possibilities:

    1. It’s a second Higgs boson! Many extensions to the Standard Model — like supersymmetry — predict additional Higgs particles that are heavier than the current (126 GeV) one we know. If so, this could be a window into a whole world of physics beyond the Standard Model, including into the matter/antimatter asymmetry and the Hierarchy problem.
    2. It’s dark matter-related. Could this new particle be a window into the dark sector? Is there some energy non-conservation happening here that means we’re making something that the detectors can’t see? This is one of the “dare-to-dream” possibilities of particle physics: that the LHC could create dark matter. There’s even a fun little correlation here with something most people haven’t put together: there’s an excess in cosmic ray energies seen in this exact same energy range from the balloon-borne Advanced Thin Ionization Calorimeter (ATIC) experiment!

    8
    Image credit: J. Chang et al. (2008), Nature, from the Advanced Thin Ionization Calorimeter (ATIC).

    3.It’s a window into extra dimensions. If there are more than the three spatial dimensions we’re used to, especially at smaller scales, new particles can arise in our three dimensions as a result. These Kaluza-Klein particles could show up at the LHC, and might decay to two photons. Studying how they decay could tell us whether this is true.

    4.It’s a new part of the neutrino sector. This would be a little unusual — since neutrinos don’t normally decay to two photons; they’ve got the wrong spin — but a scalar neutrino could create two photons, which is actually a thing in Standard Model extensions. The couplings and decay pathways, if it’s real, could show us this.

    5. It’s a composite particle. The first particle we ever saw decay into two photons was the lightest quark-antiquark combination of all: the neutral pion. Perhaps these Standard Model particles are combining in ways we don’t yet understand, and what we’ve found is nothing new.
    Or, most excitingly, none of the above. The most exciting discoveries are the ones you never anticipated, and perhaps it isn’t any of the speculative scenarios we know to look for. Perhaps nature is more surprising than even our wildest theoretical dreams.

    6. Or, most excitingly, none of the above. The most exciting discoveries are the ones you never anticipated, and perhaps it isn’t any of the speculative scenarios we know to look for. Perhaps nature is more surprising than even our wildest theoretical dreams.

    The answers, believe it or not, are locked inside of the smallest particles in nature. All we need are the highest energies we can get to in order to find out.

    Of course, this could simply turn out to be a statistically insignificant bump that goes away with more data; it may be nothing at all. This has already happened once before, at about three times the energy. There was hint of an extra “bump” at just over 2 TeV in both detectors, as you can see for yourself.

    7
    Images credit: ATLAS collaboration (L), via http://arxiv.org/abs/1506.00962; CMS collaboration (R), via http://arxiv.org/abs/1405.3447.

    A reanalysis of the data shows there’s no significance to this signal, and that might be what we have in the 750 GeV case, too. But the possibility that it’s real is too big to ignore, and the data will come in to tell us by the end of this year. The biggest unanswered, fundamental questions in theoretical physics will get a run for the money, and all it takes is for a bump in the data to hold up a little bit longer.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 4:33 pm on May 17, 2016 Permalink | Reply
    Tags: , , ,   

    From CERN: “How to help CERN to run more simulations” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    16 May 2016
    by The LHC@home team

    With LHC@Home you can actively contribute to the computing capacity of the Laboratory!

    LHC Sixtrack

    You may think that CERN’s large Data Centre and the Worldwide LHC Computing Grid have enough computing capacity for all the Laboratory’s users. However, given the massive amount of data coming from LHC experiments and other sources, additional computing resources are always needed, notably for simulations of physics events, or accelerator and detector upgrades.

    This is an area where you can help, by installing BOINC and running simulations from LHC@home on your office PC or laptop. These background simulations will not disturb your work, as BOINC can be configured to automatically stop computing when your PC is in use.

    BOINC WallPaper

    BOINCLarge

    As mentioned in earlier editions of the Bulletin (see here and here), contributions from LHC@home volunteers have played a major role in LHC beam simulation studies.

    LHC@Home Classic Users 133,627 Hosts (computers) 359,237 Teams 5,079 Countries 205 Total BOINC credit 4,797,971,717
    Last day 205,687
    (Statistics from BOINCStats)

    The computing capacity they made available corresponds to about half the capacity of the CERN batch system! Thanks to this precious contribution, detailed studies of subtle effects related with non-linear beam dynamics have been performed using the SixTrack code. This proved extremely useful not only for the LHC, but also for its upgrade, the HL-LHC.

    More recently, thanks to virtualisation, the use of LHC@home has been expanded to other applications. Full physics simulations are run in a small CernVM virtual machine on all types of volunteer computers. Monte-Carlo simulations for theorists were first included in a project called Test4Theory. Results are submitted to a database called MCPLots, based in the Theory department at CERN. Since 2011, about 2.7 trillion events have been simulated.

    Following this success, ATLAS became the first experiment to join, and the number of volunteers engaged in ATLAS physics events simulation has been steadily ramping up for the last 18 months. The production rate is now equivalent to that of a large WLCG Tier 2 site! These events are fully integrated into the experiment data management system and are already being used for the physics analysis of Run 2. Now applications for the other LHC experiments are also being tested under LHC@home.

    We encourage you to help to produce more results. It is really easy to join! On a standard CERN NICE PC, you can install BOINC with CMF, and then connect to LHC@home as indicated on the LHC@home web-site and in the CMF instructions. If you use a Macintosh or Linux desktop, please refer to the instructions for your platform on the website, which also includes a video tutorial.

    Help our accelerator and research community and join LHC@home!

    [This subject is near and dear to my heart. For about six years I was a “cruncher”. I worked on Six Track and Test4Theory for CERN. In total, all projects I amassed 37,000,000 credits before I had to quit. I still believe in Public Distributed Computing. I support BOINC and World Community Grid on this blog when something is published.]

    See the full article here.

    Please help promote STEM in your local schools.

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    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
  • richardmitnick 9:07 am on May 14, 2016 Permalink | Reply
    Tags: , , Boston U Bump Hunters, , , , ,   

    From BU: “Bump Hunters” 

    Boston University Bloc

    Boston University

    5.14.16
    Elizabeth Dougherty

    Boston U Bump Hunters Steve Ahlen, Kenneth Lane, Tulika Bose, Kevin Black, Sheldon Glashow
    Bump Hunters Steve Ahlen, Kenneth Lane, Tulika Bose, Kevin Black, Sheldon Glashow

    Tulika Bose stands guard over the printer.

    She’s carried her laptop down the hall and submitted her print job on arrival to be certain that she will intercept her papers before anyone else has a chance to see them. Her documents contain secrets.

    Bose is a physicist working at the Large Hadron Collider (LHC) in Switzerland.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    Her work has nothing to do with weapons or national defense or space exploration or any of the usual top-secret stuff physicists work on. What her files contain are ideas about what we—everything under the sun and beyond it—are made of. Her documents could contain the secrets of the universe.


    Access mp4 video here .
    When Protons Collide: A proton collision is like a car accident—except when it isn’t. Physicist Kevin Black explains why. (Watch out for the kitchen sink!) Video by Joe Chan

    An associate professor of physics at Boston University, Bose is part of a cadre of physicists at BU committed to understanding matter down to its smallest particles and most intricate interactions. BU is unusual, one of only a small handful of US universities with researchers working on multiple experiments at the LHC.

    These experiments are looking for signs of particles that have never been seen before. The particles familiar from high school physics—electrons, protons, and neutrons—were just the beginning. Over the past several decades, physicists have confirmed that there are six kinds of quarks; three types of leptons; and assorted bosons, including photons, gluons, and the famed Higgs. These particles only exist in high-energy environments, such as the LHC, where protons are sent hurtling around a ring at speeds very close to the speed of light, colliding together spectacularly. All of the particles that are predicted to exist by the accepted theory of particle physics, called the Standard Model, have been found through experiments like those done at the LHC.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    2
    A theoretical physicist since the 1960s and a Nobel Laureate, Glashow came to BU in 2000 because of the physics department’s emphasis on experiments like those at the LHC. Photo by Gina Manning

    U also happens to have on its faculty Sheldon Glashow, a BU College of Arts & Sciences physics professor, who won the Nobel Prize in Physics in 1979 for his work developing the foundations of the Standard Model. Theorists like Glashow and Kenneth Lane, also a BU professor of physics, and experimental physicists like Bose have become masters of the Standard Model and are spending their careers trying to figure out one thing: Is there more to the universe than what we know right now?

    The answer, almost surely, is yes.

    When physicists look for new particles, they are really looking for “bumps” in the data produced by their experiments. A bump indicates that something appeared with energy or mass that was different than expected. “We call it ‘bump hunting,’” says Steve Ahlen, BU professor of physics, who represents yet another flavor of physicist. A hardware physicist, Ahlen has built muon detector chambers with his own hands and led their construction in Boston. Those built in Boston were auspiciously placed at the LHC and captured a good portion of the particles that allowed researchers to confirm the existence of the Higgs boson in 2012.

    The hunt is on, at a time like no other in physics. The quest reached a pinnacle with the Higgs boson, but finding it wasn’t the end. It was just the beginning.

    “Before the Higgs was discovered, people were absolutely convinced that it was there. The challenge was finding it,” says Glashow. “The trouble now is that we theorists don’t know what else is out there. We are no longer so confident that we know what to look for. But we hope that something interesting will show up.”

    On Colliders and Detectors

    The Large Hadron Collider is currently the world’s highest energy particle collider. It is also the largest machine ever built. The circular tunnel around which proton beams fly is 17 miles wide and buried 574 feet underground in a rural area on the border of France and Switzerland at the European Organization for Nuclear Research (CERN). The collider’s job is to smash particles together at high speeds and record the spray of shrapnel that results, so that physicists can look for signs of new particles. If they find something that looks interesting, they piece the data back together again, retracing the paths of all the particles in the spray back to the collision that caused them.

    “I think of it as if a murder has happened, and you have all these clues,” says Bose. “The detective comes in and uses all these clues to reconstruct the scene and figure out who committed the crime.”

    In 2015, the LHC operated at 13 tera-electron-volts (TeV), the highest energy level yet. One TeV is a trillion electron-volts, which sounds like a lot. It is, but it is small compared to the energy consumed by light bulbs and laptops and other things of daily life. A tera-electron-volt is approximately equal to the energy of a single flying mosquito. What the LHC does, beyond multiplying that energy by 13, is compress it into the space of a proton beam, a million million times smaller than a mosquito.

    At this energy level, the LHC can accelerate protons to speeds extremely close to the speed of light. Further, it bundles those protons, with each beam containing a thousand bunches of about a hundred billion protons per bunch. Packing far more punch than a mosquito, the total energy of a beam is more like a 17-ton plane flying over 460 miles per hour.

    In March 2016, the collider began running again, this time with more intense beams. This increased brightness will make for more collisions per second, so the LHC will produce approximately six times more data than in 2015. “We’re just beginning to tap its potential,” says Kevin Black, an associate professor of physics at BU, and also Bose’s husband. Bose and her students work on an experiment called CMS at LHC. Black works on a different experiment there called ATLAS.

    The CMS and ATLAS experiments are, at their core, two different pieces of hardware that detect particles.

    CERN/CMS Detector
    CERN CMS Higgs Event
    CERN/CMS and Higgs event at CMS

    CERN/ATLAS
    CERN ATLAS Higgs Event
    CERN/ATLAS andHiggs event at ATLAS

    They sit at opposite sides of the beam ring surrounding two separate beam intersections, where they capture all of the shrapnel from the proton-proton collisions that occur at their centers.

    The ATLAS detector, which Ahlen helped build, is a 75-foot-high, 140-foot-long machine in which five layers of detection hardware measure the momentum and mass of particles produced when protons smash together. CMS, for Compact Muon Solenoid, is considerably smaller and more dense. It captures the same types of particles as ATLAS, just in a different way.

    2
    A hands-on physicist, Ahlen likes to build things. He is currently building dark energy detectors and climbing mountains to install them on telescopes. Photo by Gina Manning

    These machines can detect all of the particles defined in the Standard Model. Take muons as an example. A muon is a tiny particle, even by the standards of particle physicists, that is produced inside colliders and also when cosmic rays strike the atmosphere. When Ahlen got involved with the development of detectors for particle colliders in the 1990s, it wasn’t clear how to detect muons affordably. He came up with a simple solution: A twelve-foot-long, two-inch-diameter aluminum tube, crimped at both ends and filled with gas, with a wire stretched under tension from end to end. “If you pressurize it, it can localize the trajectory of a particle that passes through the tube,” he says, waving around a spare tube he keeps behind the door in his office.

    The ATLAS detector, which has several layers of specialized particle detectors, contains about 500,000 of these tubes. They were built all over the world to exacting standards, many in Boston by Ahlen, who borrowed and bartered equipment and materials to get the job done.

    While the tubes themselves might not seem so special, keep in mind that each tube in the ATLAS detector must be precisely placed. “We know where each wire is to less than the width of a human hair,” says Ahlen.

    Not only that, every particle that whizzes by must be recorded, along with the exact time it flew through. So every tube and every other sensor in the detector—tens of millions of them in total—is connected to a clock. The clocks are set to the beam crossing, which occurs every 25 nanoseconds. The first crossing is one. “The second, two, the third, three,” says Ahlen. “Every 25 nanoseconds, boom, boom.”

    There were 40 million beam crossings per second, and about a billion proton-proton collisions per second, in the last run of the LHC.

    The time-stamped data flows from each detector down an electrical pipe to join with others in a raging river of data. Carefully coded computer algorithms determine which events to keep and which to throw away. Bose, who is the “trigger” in charge of this gatekeeping for CMS, saves only about a thousand events per second. A lot, but still just a tiny fraction of the data produced.

    Secret Keepers

    CMS and ATLAS produce and save independent sets of data and have independent teams analyzing it. Bose, for example, is one of nearly 4,000 people working on the CMS experiment, while Black is part of a team of 3,000 people working on ATLAS.

    The teams sift through their data in secret, without sharing early results. At a time when data sharing in science is all the rage, secrecy seems to go against the grain, but it is a necessity in physics. In the past, there have been cases where rumors about the early sightings of new particles lead to false discoveries. In one case, physicists started looking for signs of a new particle people were buzzing about. “Any run that had a little bump in the rumored location, they kept,” says Black. “Anything that didn’t, they found a reason to throw out the data. Inadvertently, they self-selected the particle into existence.” In the end, an unbiased look at the data proved that the particle did not exist.

    3
    For Black (PhD ’05), who is currently stationed at the LHC in Switzerland, patience is a virtue. The phenomena he studies occur so rarely that even with millions of collisions per second, he might not see them. Photo by Darrin Vanselow

    So experimentalists like Bose and Black try not to share data. In fact, they try extra hard, since the two are married. “We don’t talk about the details,” says Black. “I think we actually have more of a dividing line there because we are worried that if there is any leak, people might look to us first.”

    In practice, though, that line is a bit murky. The thousands of scientists at the LHC work side-by-side. The offices of scientists on different experiments are intermeshed. They share cafeterias and printers and hold open-door seminars to discuss ideas. Despite all this openness, no one wants to undermine the credibility of the science they are doing. “From a pure science point of view, the result is much stronger when two independent experiments come up with the same answer without biasing each other,” says Bose. “We try to keep an open mind. You look everywhere and you see what you see.”

    In the end, it isn’t just secrecy that keeps the science pure. Particle physicists have also set a very high bar for discovery. For a new particle to be accepted, scientists must be confident that it is not a statistical fluctuation. They’ve agreed on a number, 5-sigma, which means that the chance of the data being a statistical fluctuation is 1 in 3.5 million.

    The concept of sigma might be familiar from basic statistics—or from tests graded on a curve. One standard deviation from the mean on a bell curve is called one-sigma. Students scoring two- or three-sigma above (or below) are rare and end up with the grades to prove it.

    But the LHC doesn’t make its findings based on a single test. A bump at the LHC stands out against the bell curves of all the tests ever run. This mass of data all taken together, says Bose, is called “background.” It forms a landscape that has become familiar to physicists. A bump like the Higgs appears as a blot on this predictable landscape, a little like the unexpected genius who shows up for test after test and busts the curve.

    The bump that physicists recognized as the first sign of the Higgs boson was produced by data from about 10 collisions. Even with such scant data, the confidence level was about 4-sigma because the Higgs stood out so starkly against the familiar background. Later, when all of the data came together, about 40 events produced a more pronounced bump with a confidence level of 8-sigma. “That’s a very clean discovery,” says Ahlen.

    From Old Physics, New

    The LHC fired up its proton beams again in March 2016, and saw its first collisions on April 23. The hope is that at the planned higher energy level, it will produce more dramatic collisions that will allow physicists to discover something new.

    “The best thing that could happen is that we’ll discover a whole set of new particles that don’t make any sense at all,” says Black. “I’m hopeful that sort of thing will happen, that we’ll discover something that truly doesn’t make sense and we’ll really learn something from it.”

    Physicists refer to their quest as a search for “new physics,” begging the question: What’s wrong with the old physics? It’s not so much that the old physics doesn’t work—it does, amazingly well—but ask any particle physicist, and they will tell you there’s something about it that just isn’t satisfying. Parameters have to line up in very specific ways for some calculations to work out. If something is off by a smidgen, everything falls apart.

    “This kind of special balancing out of parameters in the current theory gives us the impression that there has to be some underlying principle that we’re missing,” says Black.

    So it is and so it has always been in physics. It all started back when the Greeks came up with the solid but incomplete idea of the atom. Centuries later, Newton’s experiments resulted in Newtonian mechanics, which brilliantly explain the day-to-day physics of the movements of planets in space and objects on Earth. Things got heady in the late 1800s when scientists started to understand electrical currents and magnetic fields. The early 20th century gave rise to quantum theory, which explains the world of tiny, energetic things, like photons. According to Lane, every successful theory has engulfed its predecessor. “Quantum mechanics ate the physics of the 18th and 19th centuries alive,” he says.

    The most recent meal, so to speak, was devoured in the 1960s and 70s by the Standard Model. By 1960, physicists knew about weak nuclear forces, which govern how particles decay into other particles. But no one knew how this force was related to existing theories of electromagnetism. Glashow worked out a new model for weak nuclear forces that relied on three new particles.

    “No one cared,” he says, until 1967, when Glashow’s idea morphed, in a confluence of other ideas, into a theory that made sense: The Standard Model. “Experimenters went out of their way to verify the predictions of the theory,” says Glashow, who won the Nobel Prize alongside Steven Weinberg and Abdus Salam for their work. “Lo and behold, the theory was right.”

    For theorists like Glashow and Lane, the observations of experiments lend credence to theory, and theory provides a rationale for understanding and deciphering what is seen in experiments. “Physics is an experimental science,” says Lane. “It’s not mathematics or philosophy. If it can’t be tested by experiment, it ain’t physics.”

    The most recent piece of experimental data confirming the Standard Model was the discovery of the Higgs boson in 2012. For Lane, the Higgs was a bit of a disappointment. “It’s kind of a simple-minded solution to a big problem,” he says. “Some people still feel burned by this discovery. Me, for example.”

    But ultimately, Lane is interested in figuring out what the most basic, fundamental particles are and how they interact with one another. “Right now, we have a story for that, but there’s always been a story for that,” he says.

    As long as people have been curious about the world they live in, they’ve been coming up with theories, testing them, and making them better. “This,” says Lane, “is an enterprise that need have no end.”

    See the full article here .

    Please help promote STEM in your local schools.

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    Boston University is no small operation. With over 33,000 undergraduate and graduate students from more than 130 countries, nearly 10,000 faculty and staff, 17 schools and colleges, and 250 fields of study, our two campuses are always humming, always in high gear.

    Boston University Campus
    BU Campus

     
  • richardmitnick 1:52 pm on May 13, 2016 Permalink | Reply
    Tags: , , , , , ,   

    From FNAL: “What do theorists do?” 

    FNAL II photo

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    May 13, 2016
    Leah Hesla
    Rashmi Shivni

    1
    Pilar Coloma (left) and Seyda Ipek write calculations from floor to ceiling as they try to find solutions to lingering questions about our current models of the universe. Photo: Rashmi Shivni, OC

    Some of the ideas you’ve probably had about theoretical physicists are true.

    They toil away at complicated equations. The amount of time they spend on their computers rivals that of millennials on their hand-held devices. And almost nothing of what they turn up will ever be understood by most of us.

    The statements are true, but as you might expect, the resulting portrait of ivory tower isolation misses the mark.

    The theorist’s task is to explain why we see what we see and predict what we might expect to see, and such pronouncements can’t be made from the proverbial armchair. Theorists work with experimentalists, their counterparts in the proverbial field, as a vital part of the feedback loop of scientific investigation.

    “Sometimes I bounce ideas off experimentalists and learn from what they have seen in their results,” said Fermilab theorist Pilar Coloma, who studies neutrino physics. “Or they may find something profound in theory models that they want to test. My job is all about pushing the knowledge forward so other people can use it.”

    Predictive power

    Theorists in particle physics — the Higgses and Hawkings of the world — push knowledge by making predictions about particle interactions. Starting from the framework known as the Standard Model, they calculate, say, the likelihood of numerous outcomes from the interaction of two electrons, like a blackjack player scanning through the possibilities for the dealer’s next draw.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Experimentalists can then seek out the predicted phenomena, rooting around in the data for a never-before-seen phenomenon.

    Theorists’ predictions keep experimentalists from having to shoot in the dark. Like an experienced paleontologist, the theorist can tell the experimentalist where to dig to find something new.

    “We simulate many fake events,” Coloma said. “The simulated data determines the prospects for an experiment or puts a bound on a new physics model.”

    The Higgs boson provides one example.

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    By 2011, a year before CERN’s ATLAS and CMS experiments announced they’d discovered the Higgs boson, theorists had put forth nearly 100 different proposals by as many different methods for the particle’s mass. Many of the predictions were indeed in the neighborhood of the mass as measured by the two experiments.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    CERN/ATLAS
    CERN/ATLAS

    CERN/CMS Detector
    CERN/CMS Detector

    And like the paleontologist presented with a new artifact, the theorist also offers explanations for unexplained sightings in experimentalists’ data. She might compare the particle signatures in the detector against her many fake events. Or given an intriguing measurement, she might fold it into the next iteration of calculations. If experimentalists see a particle made of a quark combination not yet on the books, theorists would respond by explaining the underlying mechanism or, if there isn’t one yet, work it out.

    “Experimentalists give you information. ‘We think this particle is of this type. Do you know of any Standard Model particle that fits?’” said Seyda Ipek, a theorist studying the matter-antimatter imbalance in the universe. “At first it might not be obvious, because when you add something new, you change the other observations you know are in the Standard Model, and that puts a constraint on your models.”

    And since the grand aim of particle physics theory is to be able to explain all of nature, the calculation developed to explain a new phenomenon must be extendible to a general principle.

    “Unless you have a very good prediction from theory, you can’t convert that experimental measurement into a parameter that appears in the underlying theory of the Standard Model,” said Fermilab theorist John Campbell, who works on precision theoretical predictions for the ATLAS and CMS experiments at the Large Hadron Collider.

    Calculating moves

    The theorist’s calculation starts with the prospect of a new measurement or a hole in a theory.

    “You look at the interesting things that an experiment is going to measure or that you have a chance of measuring,” Campbell said. “If the data agrees with theory everywhere, there’s not much room for new physics. So you look for small deviations that might be a sign of something. You’re really trying to dream up a new set of interactions that might explain why the data doesn’t agree somewhere.”

    In its raw form, particle physics data is the amount and location of the energy a particle deposits in a particle detector. The more sensitive the detector, the more accurate the experimentalists’ measurement, and the more precise the corresponding calculation needs to be.

    2
    Fermilab theorists John Campbell (left) and Ye Li work on a calculation that describes the interactions you might expect to see in the complicated environment of the LHC. Photo: Rashmi Shivni

    The CMS detector at the Large Hadron Collider, for example, allows scientists to measure some probabilities of particle interactions to within a few percent. And that’s after taking into account that it takes one million or even one billion proton-proton collisions to produce just one interesting interaction that CMS would like to measure.

    “When you’re making the measurement that accurately, it demands a prediction at a very high level,” Campbell said. “If you’re looking for something unexpected, then you need to know the expected part in quite a lot of detail.”

    A paleontologist recognizes the vertebra of a brachiosaurus, and the theoretical particle physicist knows what the production of a pair of top quarks looks like in the detector. A departure from the known picture triggers him to take action.

    “So then you embark on this calculation,” Campbell said.

    Embark, indeed. These calculations are not pencil-and-paper assignments. A single calculation predicting the details of a particle interaction, for example, can be a prodigious effort that takes months or years.

    So-called loop corrections are one example: Theorists home in on what happens during a particle event by adding detail — a correction — to an approximate picture.

    Consider two electrons that approach each other, exchange a photon and diverge. Zooming in further, you predict that the photon emits and reabsorbs yet another pair of particles before it itself is reabsorbed by the electron pair. And perhaps you predict that, at the same time, one of the electrons emits and reabsorbs another photon all on its own.

    Each additional quantum-scale effect, or loop, in the big-picture interaction is like pennies on the dollar, changing the accounting of the total transaction — the precision of a particle mass calculation or of the interaction strength between two particles.

    With each additional loop, the task of performing the calculation becomes that much more formidable. (“Loop” reflects how the effects are represented pictorially in Feynman diagrams — details in the approximate picture of the interaction.) Theorists were computing one-loop corrections for the production of a Higgs boson arising from two protons until 1991. It took another 10 years to complete the two-loop corrections for the process. And it wasn’t until this year, 2016, that they finished computing the three-loop corrections. Precise measurements at the Large Hadron Collider would (and do) require precise predictions to determine the kind of Higgs boson that scientists would see, demanding the decades-long investment.

    “Doing these calculations is not straightforward, or we would have done them a long time ago,” Campbell said.

    Once the theorist completes a calculation, they might publish a paper or otherwise make their code broadly available. From there, experimentalists can use the code to simulate how it will look in the detector. Farms of computers map out millions of fake events that take into account the new predictions provided courtesy of the theorist.

    “Without a network of computers available, our studies can’t be done in a reasonable time,” Coloma said. “A single computer can not analyze millions of data points, just as a human being could never take on such a task.”

    If the simulation shows that, for example, a particle might decay in more ways than what the experiment has seen, the theorist could suggest that experimentalists expand their search.

    “We’ve pushed experiments to look in different channels,” Ipek said. “They could look into decays of particles into two-body states, but why not also 10-body states?”

    Theorists also work with an experiment, or multiple experiments, to put their calculations to best use. Armed with code, experimentalists can change a parameter or two to guide them in their search for new physics. What happens, for example, if the Higgs boson interacts a little more strongly with the top quark than we expect? How would that change what we see in our detectors?

    “That’s a question they can ask and then answer,” Campbell said. “Anyone can come up with a new theory. It is best to try to provide a concrete plan that they can follow.”

    Outlandish theories and concrete plans

    Concrete plans ensure a fruitful relationship between experiment and theory. The wilder, unconventional theories scientists dream up take the field into exciting, uncharted territory, but that isn’t to say that they don’t also have their utility.

    Theorists who specialize in physics beyond the Standard Model, for example, generate thousands of theories worldwide for new physics – new phenomena seen as new energy deposits in the detector where you don’t expect to see them.

    “Even if things don’t end up existing, it encourages the experiment to look at its data in different ways,” Campbell said. An experiment could take so much data that you might worry that some fun effect is hiding, never to be seen. Having truckloads of theories helps mitigate against that. “You’re trying to come up with as many outlandish ideas as you can in the hope that you cover as many of those possibilities as you can.”

    Theorists bridge the gap between the pure mathematics that describes nature and the data through which nature manifests.

    “The field itself is challenging, but theory takes us to new places and helps us imagine new phenomena,” Ipek said.” We collectively work toward understanding every detail of our universe and that’s what ultimately matters most.”

    See the full article here .

    Please help promote STEM in your local schools.

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    Fermilab Campus

    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 1:03 pm on May 13, 2016 Permalink | Reply
    Tags: , , , , quasiparticle collider   

    From NOVA: “Quasiparticle Collider Could Illuminate Mysteries of Superconductivity” 

    PBS NOVA

    NOVA

    When a marten—a small, weasel-like animal—crawled inside a transformer and shut down the Large Hadron Collider, it highlighted the risks of giant science experiments. The bigger the facility, the more chances for the unexpected. Physicists use the Large Hadron Collider (LHC), a 17-mile vacuum tube buried under Geneva, Switzerland, to speed up subatomic particles to near the speed of light and smash them together.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC, 17 mile circular accelerator at CERN

    But a team of scientists has developed a marten-proof way to collide particles—using a device the size of a tabletop.

    Made up of no more than a laser and a tiny crystal, the technique studies different kinds of particles than the LHC does. They’re called quasiparticles. Quasiparticles are, in essence, disturbances that form in a material that can be classified—and modeled—as particles in their own right (even though they are not actual particles). For example, an electron quasiparticle is made up of an electron moving through a medium (in this particular study, a semiconductor crystal), plus the perturbations its negative charge causes in neighboring electrons and atomic nuclei.

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    A quantum dot—a nanoscale semiconductor device that tightly packs electrons and electron holes—glows a specific color when it is hit with any kind of light. The team’s new quasiparticle collider could help scientists develop more efficient light-emitting tools, beyond what the quantum dot can do.

    Another example of a quasiparticle that acts as a counterpart to the electron quasiparticle is an electron hole, defined as the lack of electrons in a space surrounded by electrons. In other words, a “hole” quasiparticle is equivalent to a positively charged gap left by an electron on-the-go. So although quasiparticles a little different from what we usually think of as a particle, they’re sort of like air bubbles moving through water. Here’s Elizabeth Gibney, reporting for Nature News:

    It is intuitive for physicists to think in terms of quasiparticles, in the same way that it makes sense to follow a moving bubble in water, rather than trying to chart every molecule that surrounds it, says Mackillo Kira, a physicist at the University of Marburg in Germany and co-author of a report on the quasiparticle collider, published in Nature.

    Usually, the electron quasiparticle and the hole quasiparticle are bound up as a compound quasiparticle called an exciton. Their opposite charges pull them together. But with powerful laser pulses, physicists can cleave the exciton back into its component parts, which rush away from each other. Then they swing back and collide at high speed, producing light particles called photons. The physicists are able to detect the photons, which let them study what happened in the quasiparticle collision.

    Those photons could hold the secrets of how quasiparticles are structured. Though they’re only around for tiny fractions of a second, quasiparticles are an important part of physics. Since quasiparticles form when light is emitted, the new technique could illuminate a way to build better solar cells or to study strange forms of matter such as superconductors, since so-called Bogoliubov quasiparticles represent half of the electron pairs required for superconductivity.

    See the full article here .

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