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  • richardmitnick 12:01 pm on July 9, 2017 Permalink | Reply
    Tags: , , CERN ATLAS, , , , Probing physics beyond the Standard Model with heavy vector bosons   

    From ATLAS: “Probing physics beyond the Standard Model with heavy vector bosons” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    8th July 2017
    ATLAS Collaboration

    1
    Figure 1: The reconstructed mass of the selected candidate events decaying to WW or ZZ bosons, with the qqqq final state. The black markers represent the data. The blue and green curves represent the hypothesized signal for two different masses. The red curve represents the Standard Model processes. (Image: ATLAS Collaboration/CERN)

    Although the discovery of the Higgs boson by the ATLAS and CMS Collaborations in 2012 completed the Standard Model, many mysteries remain unexplained. For instance, why is the mass of the Higgs boson so much lighter than one would expect and why is gravity so weak?

    CERN CMS Higgs Event


    CERN ATLAS 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.

    Numerous models beyond the Standard Model attempt to explain these mysteries. Some explain the apparent weakness of gravity by introducing additional dimensions of space in which gravity propagates. One model goes beyond that, and considers the real world as a higher-dimensional universe described by warped geometry, which leads to strongly interacting massive graviton states. Other models propose, for example, additional types of Higgs bosons.

    All these models predict the existence of new heavy particles that can decay into pairs of massive weak bosons (WW, WZ or ZZ). The search for such particles has benefited greatly from the increase in the proton–proton collision energy during Run 2 of the Large Hadron Collider (LHC).

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    The search for new heavy particles has benefited greatly from the LHC’s increase in proton–proton collision energy.
    _______________________________________________________________________

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    Figure 2: The limit on the cross-section times branching ratio of hypothetical particle described by one of the models for the different final states. (Image: ATLAS Collaboration/CERN)

    The W and Z bosons are carrier particles that mediate the weak force. They decay into other Standard Model particles, like charged leptons (l), neutrinos (ν) and quarks (q). These particles are reconstructed differently in the detector. Quarks, for instance, are reconstructed as localized sprays of hadrons, denoted jets. The two bosons could yield several combinations of these particles in the final states. The ATLAS Collaboration has released results on searches involving all relevant decays of the boson pair: ννqq, llqq, lνqq and qqqq (where the lepton is an electron or muon).

    What do these searches have in common? In each of these, at least one of the bosons decays into a pair of quarks. When the sought-after particle is very massive, the two bosons from its decay are ejected with such large momenta that their respective decay products are collimated and the pair of quarks merge into a single large jet. This phenomenon provides a powerful means to distinguish the new physics signal from strong-interaction Standard Model processes. As some exemplary results of the searches, Figure 1 shows the distributions of the reconstructed mass of the candidate particle. Figure 2 shows the limit on the cross-section times branching ratio of a hypothetical particle described by one of the models.

    So far, no evidence of a new particle has been observed. The search continues with increased sensitivity as ATLAS collects more data.

    Links:
    See the full article for further references with links.

    See the full article here .

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  • richardmitnick 7:00 am on July 7, 2017 Permalink | Reply
    Tags: , CERN ATLAS, , , ,   

    From ATLAS: “Why should there be only one? Searching for additional Higgs Bosons beyond the Standard Model” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    6th July 2017
    ATLAS Collaboration

    1
    Figure 1: Feynman diagram for leading order production of a neutral MSSM Higgs boson in association with b-quarks. (Image: ATLAS Collaboration/CERN)

    CERN CMS Higgs Event

    Since the discovery of the elusive Higgs boson in 2012, researchers have been looking beyond the Standard Model to answer many outstanding questions. An attractive extension to the Standard Model is Supersymmetry (SUSY), which introduces a plethora of new particles, some of which may be candidates for Dark Matter.

    Standard model of Supersymmetry DESY

    One of the most popular SUSY models – the Minimal Supersymmetric Standard Model (MSSM) – predicts the existence of five Higgs bosons. In this model, the recently discovered Higgs boson (h) would be considered to be the lightest of the set. Two charged Higgs (H+, H–) and two neutral Higgs (A/H) would complete the set, and could exist within a wide range of masses above that of the discovered Higgs boson. The LHC experiments are poised to search for these additional bosons using techniques similar to those used in the initial Higgs searches.

    In July 2017, the ATLAS collaboration presented a new result on the search for neutral (A/H) Higgs bosons decaying to two tau leptons. Taus are particularly interesting to the search as there is a stronger coupling between A/H and down-type fermions (e, μ, τ, d, s, b) for certain values of the MSSM parameter-space. This will enhance the probability of decays to tau leptons, as well as the production of A/H in association with b-quarks (Figure 1), providing a larger cross-section. Like with the Standard Model Higgs boson, gluon-fusion production of A/H remains an important production process in the MSSM to varying degrees (depending on the chosen model parameters). Thus, by classifying events by their probability of containing b-flavoured jets, the ATLAS search has been optimised for both b-associated and gluon-fusion production of A/H, respectively.

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    Figure 2 (left): The observed and expected 95% CL upper limits on the production cross section times di-tau branching fraction for a scalar boson produced via b-associated production. Figure 3 (right): The observed and expected 95% CL limits on tanβ as a function of the mass of the A boson in the hMSSM scenario. The area above the black curve has been excluded. The exclusion arising from the Standard Model Higgs boson coupling measurements and the exclusion limit from the ATLAS 2015 H/A→ ττ search are shown. (Images: ATLAS Collaboration/CERN)

    See the full article here .

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  • richardmitnick 1:18 pm on July 6, 2017 Permalink | Reply
    Tags: , , CERN ATLAS, Chasing the invisible, , , ,   

    From ATLAS: “Chasing the invisible” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    6th July 2017
    ATLAS Collaboration

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    Figure 1: The second highest ETmiss monojet event in the 2016 ATLAS data. A jet with pT of 1707 GeV is indicated by the green and yellow bars corresponding to the energy deposition in the electromagnetic and hadronic calorimeters respectively. The ETmiss of 1735 GeV is shown as the white dashed line in the opposite side of the detector. No additional jets with pT above 30 GeV are found. (Image: ATLAS Collaboration/CERN)

    Cosmological and astrophysical observations based on gravitational interactions indicate that the matter described by the Standard Model of particle physics constitutes only a small fraction of the entire known Universe. These observations infer the existence of Dark Matter, which, if of particle nature, would have to be 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.

    Although the existence of Dark Matter is well-established, its nature and properties still remain one of the greatest unsolved puzzles of fundamental physics. Excellent candidates for Dark Matter particles are weakly interacting massive particles (WIMPs). These “invisible” particles cannot be detected directly by collision experiments.

    At the LHC, most collisions of protons produce sprays of energetic particles that bundle together into so-called “jets”. Momentum conservation requires that if particles are reconstructed in one part of the detector there have to be recoiling particles in the opposite direction. However, if WIMPs are produced they will leave no trace in the detector, causing a momentum imbalance called “missing transverse momentum” (ETmiss). However, a pair of WIMPs can be produced together with a quark or gluon that is radiated from an incoming parton (a generic constituent of the proton) producing a jet which allows to tag this kind of events.

    The jets+ETmiss search looks at final states where a highly energetic jet is produced in association with large ETmiss. Many beyond the Standard Model theories can be probed by looking for an excess of events with large missing transverse momentum compared to the Standard Model expectation. Among those theories, Supersymmetry and models which foresee the existence of Large Extra Spatial Dimensions (LED), predict additional particles that are invisible to collider experiments. These theories could give an elegant explanation to several anomalies still unsolved in the Standard Model.

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    Figure 2: Missing transverse momentum distribution after the jets+ETmiss selection in data and in the Standard Model predictions. The different background processes are shown in different colors. The expected spectra of LED, Supersymmetric and WIMP scenarios are also illustrated with dashed lines. (Image: ATLAS Collaboration/CERN)

    The combination of data-driven techniques and high-precision theoretical calculations has allowed ATLAS to predict the main Standard Model background processes with great precision. The shape of the ETmiss spectrum is used to increase the discovery potential of the analysis and increase the discrimination power between signals and background.

    The figure shows the missing transverse momentum spectrum compared to the measurement with the Standard Model expectation. Since no significant excess is observed, the level of agreement between data and the prediction is translated into limits on unknown parameters of the Dark Matter, Supersymmetry and LED models.

    In the WIMP scenario, the latest analysis using data collected in 2015 and 2016 in a specific interaction model are able to exclude Dark Matter masses up to 440 GeV and interaction mediators up to 1.55 TeV. Under the considered model, these represent competitive results when compared with other experiments using different detection approaches.

    Over the next two years the LHC aims to increase the data available by a factor of three. This will be a unique opportunity for ATLAS to investigate the energy frontier and the jets+ETmiss channel will continue to hold the potential to profoundly revise our understanding of the universe.

    Links:

    Search for dark matter and other new phenomena in events with an energetic jet and large missing transverse momentum using the ATLAS detector (ATLAS-CONF-2017-060): link coming soon
    EPS 2017 presentation by Shin-Shan Yu: Dark matter searches at colliders
    See also the full lists of ATLAS Conference Notes and ATLAS Physics Papers.

    See the full article here .

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  • richardmitnick 12:10 pm on July 6, 2017 Permalink | Reply
    Tags: , ATLAS takes a closer look at the Higgs boson’s couplings to other bosons, CERN ATLAS, , ,   

    From ATLAS: “ATLAS takes a closer look at the Higgs boson’s couplings to other bosons” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    6th July 2017
    ATLAS Collaboration

    1
    Figures 1 and 2: Measurement of the Higgs boson production cross sections in its main production modes and normalised to the Standard Model predictions, as obtained by the H→ZZ*→4ℓ and H→γγ decay channels respectively. (Image: ATLAS Collaboration/CERN)

    Since resuming operation for Run 2, the LHC has been producing about 20,000 Higgs bosons per day in its 13 TeV proton–proton collisions. At the end of 2015, the data collected by the ATLAS and CMS collaborations were already enough to re-observe the Higgs boson at the new collision energy. Now, having recorded more than 36,000 trillion collisions between 2015 and 2016, ATLAS can perform ever more precise measurements of the properties of the Higgs boson.

    Measuring how the Higgs boson is produced and it decays is one of the major goals of the LHC experiments. Greater precision in these measurements allows us to refine our understanding of the Higgs sector of the Standard Model, and also constrain new phenomena beyond the Standard Model that would modify the coupling of the Higgs with the other Standard Model particles. By studying the Higgs boson decays to photon pairs (H→γγ) and to four leptons via intermediate Z bosons (H→ZZ*→4ℓ, where the ‘*’ indicates that one Z boson is produced off its mass shell), the ATLAS experiment can measure the coupling properties of the Higgs boson with unprecedented precision.

    At the LHC, the Higgs boson is produced through different processes with very different rates: gluon fusion, vector-boson fusion, WH, ZH, and ttH. To probe these production modes, ATLAS has introduced a set of criteria to categorize the Higgs events with the H→γγ and H→ZZ*→4ℓ final states. The results of this study are displayed in Figures 1 and 2, where the measured cross section, normalized to the value predicted by the Standard Model, is shown.

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    Combining these separate measurements allowed ATLAS to bring the experimental sensitivity closer to the precision of the Standard Model predictions.
    ___________________________________________________________________________________

    With the LHC producing an ever-increasing number of Higgs bosons, ATLAS has been able to start measuring the cross section of each production mode in different phase-spaces, setting an additional stress test for the Standard Model. These results are used to constrain possible modifications of the Higgs boson couplings from those predicted by the Standard Model. No significant deviation from the prediction has yet been observed.

    The H→γγ decay channel is also used to measure several differential cross sections for observables sensitive to Higgs boson production and decay, where good agreement was found between the data and Standard Model predictions (see Figure 4). Similar measurements have already been performed with H→ZZ∗→4ℓ decays.

    Combining these separate measurements allowed ATLAS to bring the experimental sensitivity closer to the precision of the Standard Model predictions. The total Higgs boson production cross section is measured to be 57.0 +6.0−5.9 +3.2−2.7 pb, where the first uncertainty is statistical and the second of systematic origin. The result is consistent with the Standard Model prediction of 55.6+2.4−3.4 pb. (Figure 3)

    ATLAS will continue to study the Higgs boson properties for the rest of Run 2, isolating its rare production modes and measuring its more elusive properties. Uncovering these secrets will either further cement the Standard Model, or give us insight of what lies beyond.

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    Figure 3: Total Higgs boson production cross sections measured at centre-of-mass energies of 7, 8, and 13 TeV by the H→γγ and H→ZZ*→4ℓ* channels and their combinations, compared to the Standard Model predictions. (Image: ATLAS Collaboration/CERN)

    4
    Figure 4: Transverse momentum of the Higgs boson as measured in the Hyy decay, and compared to the Standard model predictions. (Image: ATLAS Collaboration/CERN)

    Links

    Measurement of the Higgs boson coupling properties in the H→ZZ→4l decay channel at 13 TeV with the ATLAS detector (ATLAS-CONF-2017-043): link coming soon
    Measurements of Higgs boson properties in the diphoton decay channel with 36.1 fb−1 pp collision data at the center-of-mass energy of 13 TeV with the ATLAS detector (ATLAS-CONF-2017-045): link coming soon
    Combined measurements of Higgs boson production and decay in the H→ZZ*→4ℓ and H→γγ channels using 13 TeV pp collision data collected with the ATLAS experiment (ATLAS-CONF-2017-047): link coming soon
    EPS 2017 presentation by Ruchi Gupta: Measurement of the Higgs boson couplings and properties in the diphoton, ZZ and WW decay channels using the ATLAS detector : and Tamara Vazquez Schroeder Determination of the Higgs boson properties with the ATLAS detector
    See also the full lists of ATLAS Conference Notes and ATLAS Physics Papers.

    See the full article here .

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  • richardmitnick 8:35 pm on June 28, 2017 Permalink | Reply
    Tags: , CERN ATLAS, , Katie Dunne, , , , ,   

    From LBNL: Women in STEM “Berkeley Lab Intern Finds Her Way in Particle Physics” Katie Dunne 

    Berkeley Logo

    Berkeley Lab

    June 27, 2017
    Theresa Duque
    tnduque@lbl.gov
    (510) 495-2418

    1
    Intern Katherine Dunne with mentor Maurice Garcia-Sciveres. (Credit: Marilyn Chung/Berkeley Lab)

    As a high school student in Birmingham, Alabama, Berkeley Lab Undergraduate Research (BLUR) intern Katie Dunne first dreamed of becoming a physicist after reading Albert Einstein’s biography, but didn’t know anyone who worked in science. “I felt like the people who were good at math and science weren’t my friends,” she said. So when it came time for college, she majored in English, and quickly grew dissatisfied because it wasn’t challenging enough. Eventually, she got to know a few engineers, but none of them were women, she recalled.

    She still kept physics in the back of her mind until she read an article about “The First Lady of Physics,” Chien-Shiung Wu, an experimental physicist who worked on the Manhattan Project, and later designed the “Wu experiment,” which proved that the conservation of parity is violated by weak interactions. “Two male theorists who proposed parity violation won the 1957 Nobel Prize in physics, and Wu did not,” Dunne said. “When I read about her, I decided that that’s what I want to do – design experiments.”

    So she put physics front and center, and about four years ago, transferred as a physics major to the City College of San Francisco. “With Silicon Valley nearby, there are many opportunities here to get work experience in instrumentation and electrical engineering,” Dunne said. In the summers of 2014 and 2015, she landed internships in the Human Factors division at NASA Ames Research Center in Mountain View, where she streamlined the development of a printed circuit board for active infrared illumination.

    But it wasn’t until she took a class in modern physics when she discovered her true passion – particle physics. “When we got to quantum physics, it was great. Working on the problems of quantum physics is exciting,” she said. “It’s so elegant and dovetails with math. It’s the ultimate mystery because we can’t observe quantum behavior.”

    When it came time to apply for her next summer internship in 2016, instead of reapplying for a position at NASA, she googled “ATLAS,” the name of a 7,000-ton detector for the Large Hadron Collider (LHC). Her search drummed up an article about Beate Heinemann, who, at the time, was a researcher with dual appointments at UC Berkeley and Berkeley Lab and was deputy spokesperson of the ATLAS collaboration. (Heinemann is also one of the 20 percent of female physicists working on the ATLAS experiment.)

    CERN/ATLAS detector

    When Dunne contacted Heinemann to ask if she would consider her for an internship, she suggested that she contact Maurice Garcia-Sciveres, a physicist at Berkeley Lab whose research specializes in pixel detectors for ATLAS, and who has mentored many students interested in instrumentation.

    Garcia-Sciveres invited Dunne to a meeting so she could see the kind of work that they do. “I could tell I would get a lot of hands-on experience,” she said. So she applied for her first internship with Garcia-Sciveres through the Community College Internship (CCI) program – which, like the BLUR internship program, is managed by Workforce Development & Education at Berkeley Lab – and started to work with his team on building prototype integrated circuit (IC) test systems for ATLAS as part of the High Luminosity Large Hadron Collider (HL-LHC) Project, an international collaboration headed by CERN to increase the LHC’s luminosity (rate of collisions) by a factor of 10 by 2020.

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    A quad module with a printed circuit board (PCB) for power and data interface to four FE-I4B chips. Dunne designed the PCB. (Credit: Katie Dunne/Berkeley Lab)

    “For the ATLAS experiment, we work with the Engineering Division to build custom electronics and integrated circuits for silicon detectors. Our work is focused on improving the operation, testing, and debugging of these ICs,” said Garcia-Sciveres.

    During Dunne’s first internship, she analyzed threshold scans for an IC readout chip, and tested their radiation hardness – or threshold for tolerating increasing radiation doses – at the Lab’s 88-Inch Cyclotron and at SLAC National Accelerator Laboratory. “Berkeley Lab is a unique environment for interns. They throw you in, and you learn on the job. The Lab gives students opportunities to make a difference in the field they’re working in,” she said.

    For Garcia-Sciveres, it didn’t take long for Dunne to prove she could make a difference for his team. Just after her first internship at Berkeley Lab, the results from her threshold analysis made their debut as data supporting his presentation at the 38th International Conference on High Energy Physics (ICHEP) in August 2016. “The results were from her measurements,” he said. “This is grad student-level work she’s been doing. She’s really good.”

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    Katie Dunne delivers a poster presentation in spring 2017. (Credit: Marilyn Chung/Berkeley Lab)

    After the conference, Garcia-Sciveres asked Dunne to write the now published proceedings (he and the other authors provided her with comments and suggested wording). And this past January, Dunne presented “Results of FE65-P2 Stability Tests for the High Luminosity LHC Upgrade” during the “HL-LHC, BELLE2, Future Colliders” session of the American Physical Society (APS) Meeting in Washington, D.C.

    This summer, for her third and final internship at the Lab, Dunne is working on designing circuit boards needed for the ATLAS experiment, and assembling and testing prototype multi-chip modules to evaluate system performance. She hopes to continue working on ATLAS when she transfers to UC Santa Cruz as a physics major in the fall, and would like to get a Ph.D. in physics one day. “I love knowing that the work I do matters. My internships and work experience as a research assistant at Berkeley Lab have made me more confident in the work I’m doing, and more passionate about getting things done and sharing my results,” she said.

    Go here for more information about internships hosted by Workforce Development & Education at Berkeley Lab, or contact them at education@lbl.gov.

    See the full article here .

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  • richardmitnick 5:31 pm on June 27, 2017 Permalink | Reply
    Tags: , CERN ATLAS, , How to run a particle detector, , ,   

    From ATLAS: “How to run a particle detector” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    23rd June 2017
    Karola Dette

    5
    Karola Dette is a Post Doctoral Fellow at the University of Toronto, working on the tracking system upgrade for ATLAS’ high-luminosity setup. She joined the ATLAS collaboration in 2012 as a Master’s student with the University of Dortmund followed by a PhD for which she moved to CERN. During her PhD she became involved in the operation of the ATLAS detector, acting as shift leader and shifter/expert for the pixel detector.

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    Control room images. No image captions or credits.

    If you are interested in particle physics, you probably hear a lot about the huge amount of data that is recorded by experiments like ATLAS. But where does this data come from? Roughly speaking: first you have to plan, build and maintain an experiment and in the end you need people to analyse the data you’ve recorded. But what happens in between? What happens in the day-to-day life of people in the ATLAS control room, who are responsible for keeping all that great data coming?

    24 hours a day, 7 days a week, people are working at the ATLAS control room to keep the detector healthy and running. We have shifters who constantly check the subsystems of ATLAS, namely the tracking, calorimeter and muon systems. Then there are shifters who take care of the data recording itself, starting and stopping the data-taking, making sure we have the correct recording rates and monitoring the raw data that comes in. And then there is myself, acting as the shift leader.

    What does a shift leader do? Well, I’d say it is mainly talking to people. I am responsible for making sure that all the other shifters are communicating all the time to ensure that no problem goes unnoticed. If the data quality shifter sees any deviation from the expected output, she will inform me and we can follow up on what is causing this with the shifter of the affected subsystem or experts on call. This way we make sure that all the data we record is of highest quality and we don’t lose data that we could have recorded.

    That week, though, there were no stable beam collisions and therefore no “normal” data-taking going on, so what were we doing during a shift?

    When I started my shift at 3pm on 10 May 2017, the LHC was just ramping up its energy and ATLAS was already in data recording mode, ready to receive the first collisions in 2017. The first thing on your list as shift leader is to check if your crew is complete and, as you can see from the pictures of that day, we had our fair share of women working in the control room. [I have a series, Women in STEM, where I feature women one at a time. Why? Because women, especially in Physics, but I assume in all of the sciences, do not get a fair shake, and we are losing their talents.]

    _____________________________________________________________________

    24 hours a day, 7 days a week, people are working at the ATLAS control room to keep the detector healthy and running.
    _____________________________________________________________________

    After checking that all systems were working faultlessly and that the recording settings were correct, we had to wait for the LHC to find the right beam position to provide collisions in ATLAS. Only half an hour after they started to fine-tune the beams, we had the first collisions of 2017! This is an important milestone for the whole community and you can easily see how excited everybody gets by events like this by looking at the reaction of the shift crew. Everybody got up to take pictures of the event displays, showing the particle tracks of those first collisions. It feels a bit as if you are six years old again, it’s your birthday and you just got an amazing gift.

    After the beams were dumped, the data-taking was stopped to give our experts time to do stand-alone work with their systems. During this time, the experts are able to do calibrations, update parts of the software or run tests to verify former updates. My job between beam fills is mainly to take care that everybody sticks to the given time schedule. But since there is no time-crucial data-taking going on, it is a bit more relaxed than during times where we have colliding beams in the LHC. Therefore, I sometimes use this time to inform the public about what is going on with the LHC and ATLAS via my Twitter and Instagram accounts.

    See the full article here .

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  • richardmitnick 5:29 am on June 14, 2017 Permalink | Reply
    Tags: , CERN ATLAS, , More than the sum of its parts: inside the proton, ,   

    From ATLAS: “More than the sum of its parts: inside the proton” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    13th June 2017
    ATLAS Collaboration

    1
    Measured inclusive jet cross section as a function of the jet transverse momentum. The measurements are compared with theoretical calculations. (Image: ATLAS Collaboration/CERN)

    Discovered almost 100 years ago by Ernest Rutherford, the proton was one of the first particles to be studied in depth. Yet there’s still much about it that remains a mystery. Where does its mass and spin come from? What is it made of? To answer these questions, ATLAS physicists are using “jets” of particles emitted by the Large Hadron Collider (LHC) as a magnifying glass to examine the inner structure of the proton.

    The proton structure and its dynamics are described by the theory of strong interactions, quantum chromodynamics (QCD). It depicts the proton (and other hadrons) as a system of elementary particles, in this case quarks and gluons. QCD explains how these quarks and gluons interact and, consequently, what emerges from high-energy proton–proton collisions at the LHC.

    One of the remarkable features of QCD is that quarks and gluons cannot be observed as free particles. Instead, they always bind to form hadrons. QCD also predicts that “jets” of hadrons produced in LHC collisions will fly away from the interaction point in a few distinct directions. These directions correspond to those of the original quarks and gluons.

    The probability of observing a jet with certain kinematic properties (called a “cross section”) can be calculated in QCD. There is a higher probability of producing a jet with a low transverse momentum than producing a jet with high transverse momentum.

    The ATLAS detector measures jets across a wide range of transverse momenta, with the production rate varying by more than 10 orders of magnitude. Billions of jets with a transverse momentum of 100 GeV have been detected, yet we have so far only seen a few 2 TeV jets. A remarkable success of QCD is that it is able to describe this wide range of energies so accurately!

    In a recently released paper, ATLAS physicists counted how many jets of a given transverse momentum there were in the 2012 data. This was then compared to several theoretical predictions and found to be in agreement. These results are expected to constrain parameters of the proton structure.

    See the full article here .

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  • richardmitnick 11:11 am on May 24, 2017 Permalink | Reply
    Tags: , CERN ATLAS, , , , , Our failure in resolve,   

    From FNAL: “Fermilab scientists set upper limit for Higgs boson mass” 

    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.

    In 1977, theoretical physicists at Fermilab — Ben Lee and Chris Quigg, along with Hank Thacker — published a paper setting an upper limit for the mass of the Higgs boson. This calculation helped guide the design of the Large Hadron Collider by setting the energy scale necessary for it to discover the particle. The Large Hadron Collider turned on in 2008, and in 2012, the LHC’s ATLAS and CMS discovered the long-sought Higgs boson — 35 years after the seminal paper.

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    CERN CMS Higgs Event


    CERN/CMS Detector


    CERN ATLAS Higgs Event


    CERN/ATLAS detector

    Where it all started:

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    Where we failed and handed it to Europe:

    3
    Sight of the planned Superconducting Super Collider, in the vicinity of Waxahachie, Texas. Cancelled by our idiot Congress under Bill Clinton in 1993. We could have had it all.

    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 10:29 am on May 24, 2017 Permalink | Reply
    Tags: , ATLAS kicks off a new year at 13 TeV, CERN ATLAS, , ,   

    From ATLAS: “ATLAS kicks off a new year at 13 TeV” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    23rd May 2017
    Katarina Anthony

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    One of the early collision events with stable beams recorded by ATLAS on 23 May 2017, with a reconstructed muon candidate. The upper panes show transverse views of the detector and the muon spectrometer, while the lower panes show ATLAS in longitudinal cross-section and an eta-phi view of the energy deposits in the cells of the ATLAS calorimeters. (Image: ATLAS Collaboration/CERN)

    A new season of record-breaking kicked off today, as the ATLAS Experiment began recording first data for physics of 2017. This will be the LHC’s third year colliding beams at an energy of 13 tera electron volts (TeV), allowing the ATLAS Experiment to continue to push the limits of physics.

    “The ATLAS Experiment is ready to enter this new round of data-taking and we are looking forward to another exciting year of LHC physics,” says Karl Jakobs, ATLAS Spokesperson. “We will continue to explore the 13 TeV energy frontier in great depth, to address rarer processes and to increase the precision of many measurements.”

    2017 should be another excellent year for both ATLAS and the LHC, with records in luminosity set to be broken. The higher the luminosity, the more data can be gathered – and the greater the chance of observing rare processes. “The benefits of ATLAS’ fantastic performance in 2016 is clearly seen in our many new results, both in the search for new physics and in measurements of Standard Model processes,” says Dan Tovey, ATLAS Physics Coordinator. “This bodes very well for the rest of Run 2, when the threefold increase in data should give us sensitivity to the most subtle effects of ‘new physics’ in dedicated searches, and will enable us to take measurements with exquisite precision.”

    See the full article here .

    CERN LHC Map
    CERN LHC Grand Tunnel
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    LHC at CERN

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  • richardmitnick 1:25 pm on May 16, 2017 Permalink | Reply
    Tags: , , , CERN ATLAS, , Mykaela Reilly, , , ,   

    From BNL: Women in STEM – “Patchogue-Medford High School Student Builds a Remote Sensing System for ATLAS Detector Components” Mykaela Reilly 

    Brookhaven Lab

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    Patchogue-Medford High School student Mykaela Reilly (seated) with members of the ATLAS silicon tracker upgrade group in the Physics Department: (from left) Russell Burns, Alessandro Tricoli, Phil Kuczewski, Stefania Stucci, David Lynn, and Gerrit Van Nieuwenhuizen. No image credit.

    May 12, 2017
    Jane Koropsak
    jane@bnl.gov

    When Patchogue-Medford High School student Mykaela Reilly came to the U.S. Department of Energy’s Brookhaven National Laboratory as part of the High School Research Program last summer, she thought she was coming to work for one summer. She never expected that her achievements would result in her being offered to continue at the lab another year. From soldering to building prototypes to computer programming, Reilly says that during the course of the year she learned a lot about how research projects come together and form the foundations of scientific discovery.

    Reilly was tasked with learning LabView, a software system and design program that helps scientists with data acquisition and instrument control. She also programmed micro-controllers used to monitor nitrogen levels to keep humidity low, limit condensation, and maintain steady temperatures inside an experimental area. It took weeks to build the experimental components and test the software that would remotely control that equipment. But, with guidance from her mentor, Lab physicist Alessandro Tricoli of the ATLAS silicon tracker upgrade group in the Physics Department, and research team members Phil Kuczewski and Stefania Stucci, Reilly worked out the “bugs” until she built a sensing system and computer program that her mentors say works seamlessly.

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    Reilly’s success may help advance one of the most ambitious scientific projects in the world—the ATLAS detector at the Large Hadron Collider (LHC) near Geneva, Switzerland. Brookhaven scientists have played multiple roles in constructing, operating, and upgrading this particle detector, which is the size of a seven-story building and has opened up new frontiers in the human pursuit of knowledge about elementary particles and their interactions. Reilly conducted experiments using her remote monitoring program to see how electronic components, such as readout chips that could be incorporated in an upgrade at ATLAS, respond to tough environmental conditions—particularly the high level of radiation at the LHC. Radiation-resilient silicon readout chips would reduce power consumption and simplify the design of the entire tracker system at ATLAS.

    “Mykaela’s work will shed light on how we can make the readout chips more resistant to the radiation at the LHC, and how we can keep the radiation effects under control,” said Tricoli. “I applaud her success. With her talent, I hope she decides to pursue a career in science or engineering.”

    What’s next?

    Just before the posting of this story, Reilly announced her plans to attend Stony Brook University to pursue a degree in electrical engineering. “That is wonderful news,” said Tricoli. “I hope to see her back at the Lab soon.”

    When she isn’t busy soldering, programming, or building sensing systems, you can find Reilly on the ice competing on a synchronized figure skating team with her sisters. “I found that synchronized figure skating is a lot like research,” she said. “It’s about hard work, precision, and collaboration.”

    See the full article here .

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    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.
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