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  • richardmitnick 12:35 pm on July 18, 2019 Permalink | Reply
    Tags: "CMS releases open data for Machine Learning", , CERN CMS, , , ,   

    From CERN CMS: “CMS releases open data for Machine Learning” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN CMS

    17 July, 2019

    CMS has also provided open access to 100% of its research data recorded in proton–proton collisions in 2010.

    1
    (Image: Fermilab/CERN)

    The CMS collaboration at CERN has released its fourth batch of open data to the public. With this release, which brings the volume of its open data to more than 2 PB (or two million GB), CMS has now provided open access to 100% of its research data recorded in proton–proton collisions in 2010, in line with the collaboration’s data-release policy. The release also includes several new data and simulation samples. The new release builds upon and expands the scope of the successful use of CMS open data in research and in education.

    In this release, CMS open data address the ever-growing application of machine learning (ML) to challenges in high-energy physics. According to a recent paper, collaboration with the data-science and ML community is considered a high-priority to help advance the application of state-of-the-art algorithms in particle physics. CMS has therefore also made available samples that can help foster such collaboration.

    “Modern machine learning is having a transformative impact on collider physics, from event reconstruction and detector simulation to searches for new physics,” remarks Jesse Thaler, an Associate Professor at MIT, who is working on ML using CMS open data with two doctoral students, Patrick Komiske and Eric Metodiev. “The performance of machine-learning techniques, however, is directly tied to the quality of the underlying training data. With the extra information provided in the latest data release from CMS, outside users can now investigate novel strategies on fully realistic samples, which will likely lead to exciting advances in collider data analysis.”

    The ML datasets, derived from millions of CMS simulation events for previous and future runs of the Large Hadron Collider, focus on solving a number of representative challenges for particle identification, tracking and distinguishing between multiple collisions that occur in each crossing of proton bunches. All the datasets come with extensive documentation on what they contain, how to use them and how to reproduce them with modified content.

    In its policy on data preservation and open access, CMS commits to releasing 100% of its analysable data within ten years of collecting them. Around half of proton-proton collision data collected at 7 TeV center-of-mass in 2010 were released in the first CMS release in 2014, and the remaining data are included in this new release. In addition, a small sample of unprocessed raw data from LHC’s Run 1 (2010 to 2012) are also released. These samples will help test the chain for processing CMS data using the legacy software environment.

    Reconstructed data and simulations from the CASTOR calorimeter, which was used by CMS in 2010, are also available and represent the first release of data from the very-forward region of CMS. Finally, CMS has released instructions and examples on how to generate simulated events and how to analyse data in isolated “containers”, within which one has access to the CMS software environment required for specific datasets. It is also easier to search through the simulated data and to discover the provenance of datasets.

    As before, the data are released into the public domain under the Creative Commons CC0 waiver via the CERN Open Data portal. The portal is openly developed by the CERN Information Technology department, in cooperation with the experimental collaborations who release open data on it.

    See the full article here.


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  • richardmitnick 12:10 pm on July 15, 2019 Permalink | Reply
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    From CERN: “Exploring the Higgs boson “discovery channels” 

    Cern New Bloc

    Cern New Particle Event


    From CERN

    12th July 2019
    ATLAS Collaboration

    1
    Event display of a two-electron two-muon ZH candidate. The Higgs candidate can be seen on the left with the two leading electrons represented by green tracks and green EM calorimeter deposits (pT = 22 and 120 GeV), and two subleading muons indicated by two red tracks (pT = 34 and 43 GeV). Recoiling against the four lepton candidate in the left hemisphere is a dimuon pair in the right hemisphere indicated by two red tracks (pT = 139 and 42 GeV) and an invariant mass of 91.5 GeV, which agrees well with the mass of the Z boson. (Image: ATLAS Collaboration/CERN)

    At the 2019 European Physical Society’s High-Energy Physics conference (EPS-HEP) taking place in Ghent, Belgium, the ATLAS and CMS collaborations presented a suite of new results. These include several analyses using the full dataset from the second run of CERN’s Large Hadron Collider (LHC), recorded at a collision energy of 13 TeV between 2015 and 2018. Among the highlights are the latest precision measurements involving the Higgs boson. In only seven years since its discovery, scientists have carefully studied several of the properties of this unique particle, which is increasingly becoming a powerful tool in the search for new physics.

    The results include new searches for transformations (or “decays”) of the Higgs boson into pairs of muons and into pairs of charm quarks. Both ATLAS and CMS also measured previously unexplored properties of decays of the Higgs boson that involve electroweak bosons (the W, the Z and the photon) and compared these with the predictions of the Standard Model (SM) of particle physics. ATLAS and CMS will continue these studies over the course of the LHC’s Run 3 (2021 to 2023) and in the era of the High-Luminosity LHC (from 2026 onwards).

    The Higgs boson is the quantum manifestation of the all-pervading Higgs field, which gives mass to elementary particles it interacts with, via the Brout-Englert-Higgs mechanism. Scientists look for such interactions between the Higgs boson and elementary particles, either by studying specific decays of the Higgs boson or by searching for instances where the Higgs boson is produced along with other particles. The Higgs boson decays almost instantly after being produced in the LHC and it is by looking through its decay products that scientists can probe its behaviour.

    In the LHC’s Run 1 (2010 to 2012), decays of the Higgs boson involving pairs of electroweak bosons were observed. Now, the complete Run 2 dataset – around 140 inverse femtobarns each, the equivalent of over 10 000 trillion collisions – provides a much larger sample of Higgs bosons to study, allowing measurements of the particle’s properties to be made with unprecedented precision. ATLAS and CMS have measured the so-called “differential cross-sections” of the bosonic decay processes, which look at not just the production rate of Higgs bosons but also the distribution and orientation of the decay products relative to the colliding proton beams. These measurements provide insight into the underlying mechanism that produces the Higgs bosons. Both collaborations determined that the observed rates and distributions are compatible with those predicted by the Standard Model, at the current rate of statistical uncertainty.

    Since the strength of the Higgs boson’s interaction is proportional to the mass of elementary particles, it interacts most strongly with the heaviest generation of fermions, the third. Previously, ATLAS and CMS had each observed these interactions. However, interactions with the lighter second-generation fermions – muons, charm quarks and strange quarks – are considerably rarer. At EPS-HEP, both collaborations reported on their searches for the elusive second-generation interactions.
    ATLAS presented their first result from searches for Higgs bosons decaying to pairs of muons (H→μμ) with the full Run 2 dataset. This search is complicated by the large background of more typical SM processes that produce pairs of muons. “This result shows that we are now close to the sensitivity required to test the Standard Model’s predictions for this very rare decay of the Higgs boson,” says Karl Jakobs, the ATLAS spokesperson. “However, a definitive statement on the second generation will require the larger datasets that will be provided by the LHC in Run 3 and by the High-Luminosity LHC.”
    CMS presented their first result on searches for decays of Higgs bosons to pairs of charm quarks (H→cc). When a Higgs boson decays into quarks, these elementary particles immediately produce jets of particles. “Identifying jets formed by charm quarks and isolating them from other types of jets is a huge challenge,” says Roberto Carlin, spokesperson for CMS. “We’re very happy to have shown that we can tackle this difficult decay channel. We have developed novel machine-learning techniques to help with this task.”

    3
    An event recorded by CMS showing a candidate for a Higgs boson produced in association with two top quarks. The Higgs boson and top quarks decay leading to a final state with seven jets (orange cones), an electron (green line), a muon (red line) and missing transverse energy (pink line) (Image: CMS/CERN)

    The Higgs boson also acts as a mediator of physics processes in which electroweak bosons scatter or bounce off each other. Studies of these processes with very high statistics serve as powerful tests of the Standard Model. ATLAS presented the first-ever measurement of the scattering of two Z bosons. Observing this scattering completes the picture for the W and Z bosons as ATLAS has previously observed the WZ scattering process and both collaborations the WW processes. CMS presented the first observation of electroweak-boson scattering that results in the production of a Z boson and a photon.
    “The experiments are making big strides in the monumental task of understanding the Higgs boson,” says Eckhard Elsen, CERN’s Director of Research and Computing. “After observation of its coupling to the third-generation fermions, the experiments have now shown that they have the tools at hand to address the even more challenging second generation. The LHC’s precision physics programme is in full swing.”

    See the full article here .


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    Meet CERN in a variety of places:

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    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
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  • richardmitnick 12:38 pm on May 25, 2019 Permalink | Reply
    Tags: "CMS hunts for dark photons coming from the Higgs boson", , CERN CMS, , , One idea is that dark matter comprises dark particles that interact with each other through a mediator particle called the dark photon, , ,   

    From CERN CMS: “CMS hunts for dark photons coming from the Higgs boson” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN CMS

    24 May, 2019
    Ana Lopes

    1
    A proton–proton collision event featuring a muon–antimuon pair (red), a photon (green), and large missing transverse momentum. (Image: CERN)

    They know it’s there but they don’t know what it’s made of. That pretty much sums up scientists’ knowledge of dark matter.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    This knowledge comes from observations of the universe, which indicate that the invisible form matter is about five to six times more abundant than visible matter.

    One idea is that dark matter comprises dark particles that interact with each other through a mediator particle called the dark photon, named in analogy with the ordinary photon that acts as a mediator between electrically charged particles. A dark photon would also interact weakly with the known particles described by the Standard Model of particle physics, including the Higgs boson.

    Standard Model of Particle Physics (LATHAM BOYLE AND MARDUS OF WIKIMEDIA COMMONS)

    CERN CMS Higgs Event


    CERN ATLAS Higgs Event

    At the Large Hadron Collider Physics (LHCP) conference, happening this week in Puebla, Mexico, the CMS collaboration reported the results of its latest search for dark photons.

    The collaboration used a large proton–proton collision dataset, collected during the Large Hadron Collider’s second run, to search for instances in which the Higgs boson might transform, or “decay”, into a photon and a massless dark photon. They focused on cases in which the boson is produced together with a Z boson that itself decays into electrons or their heavier cousins known as muons.

    Such instances are expected to be extremely rare, and finding them requires deducing the presence of the potential dark photon, which particle detectors won’t see. For this, researchers add up the momenta of the detected particles in the transverse direction – that is, at right angles to the colliding beams of protons – and identify any missing momentum needed to reach a total value of zero. Such missing transverse momentum indicates an undetected particle.

    But there’s another step to distinguish between a possible dark photon and known particles. This entails estimating the mass of the particle that decays into the detected photon and the undetected particle. If the missing transverse momentum is carried by a dark photon produced in the decay of the Higgs boson, that mass should correspond to the Higgs-boson mass.

    The CMS collaboration followed this approach but found no signal of dark photons. However, the collaboration placed upper bounds on the likelihood that a signal would have been seen.

    Another null result? Yes, but results such as these and the ATLAS results on supersymmetry also presented this week in Puebla, while not finding new particles or ruling out their existence, are much needed to guide future work, both experimental and theoretical.

    For more details about this result, see the CMS website.

    See the full article here.


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  • richardmitnick 12:04 pm on May 14, 2019 Permalink | Reply
    Tags: >Model-dependent vs model-independent research, , , CERN CMS, , , , , , , ,   

    From Symmetry: “Casting a wide net” 

    Symmetry Mag
    From Symmetry

    05/14/19
    Jim Daley

    1
    Illustration by Sandbox Studio, Chicago

    In their quest to discover physics beyond the Standard Model, physicists weigh the pros and cons of different search strategies.

    On October 30, 1975, theorists John Ellis, Mary K. Gaillard and D.V. Nanopoulos published a paper [Science Direct] titled “A Phenomenological Profile of the Higgs Boson.” They ended their paper with a note to their fellow scientists.

    “We should perhaps finish with an apology and a caution,” it said. “We apologize to experimentalists for having no idea what is the mass of the Higgs boson… and for not being sure of its couplings to other particles, except that they are probably all very small.

    “For these reasons, we do not want to encourage big experimental searches for the Higgs boson, but we do feel that people performing experiments vulnerable to the Higgs boson should know how it may turn up.”

    What the theorists were cautioning against was a model-dependent search, a search for a particle predicted by a certain model—in this case, the Standard Model of particle physics.

    Standard Model of Particle Physics

    It shouldn’t have been too much of a worry. Around then, most particle physicists’ experiments were general searches, not based on predictions from a particular model, says Jonathan Feng, a theoretical particle physicist at the University of California, Irvine.

    Using early particle colliders, physicists smashed electrons and protons together at high energies and looked to see what came out. Samuel Ting and Burton Richter, who shared the 1976 Nobel Prize in physics for the discovery of the charm quark, for example, were not looking for the particle with any theoretical prejudice, Feng says.

    That began to change in the 1980s and ’90s. That’s when physicists began exploring elegant new theories such as supersymmetry, which could tie up many of the Standard Model’s theoretical loose ends—and which predict the existence of a whole slew of new particles for scientists to try to find.

    Of course, there was also the Higgs boson. Even though scientists didn’t have a good prediction of its mass, they had good motivations for thinking it was out there waiting to be discovered.

    And it was. Almost 40 years after the theorists’ tongue-in-cheek warning about searching for the Higgs, Ellis found himself sitting in the main auditorium at CERN next to experimentalist Fabiola Gianotti, the spokesperson of the ATLAS experiment at the Large Hadron Collider who, along with CMS spokesperson Joseph Incandela, had just co-announced the discovery of the particle he had once so pessimistically described.

    CERN CMS Higgs Event


    CERN ATLAS Higgs Event

    Model-dependent vs model-independent

    Scientists’ searches for particles predicted by certain models continue, but in recent years, searches for new physics independent of those models have begun to enjoy a resurgence as well.

    “A model-independent search is supposed to distill the essence from a whole bunch of specific models and look for something that’s independent of the details,” Feng says. The goal is to find an interesting common feature of those models, he explains. “And then I’m going to just look for that phenomenon, irrespective of the details.”

    Particle physicist Sara Alderweireldt uses model-independent searches in her work on the ATLAS experiment at the Large Hadron Collider.

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS

    Alderweireldt says that while many high-energy particle physics experiments are designed to make very precise measurements of a specific aspect of the Standard Model, a model-independent search allows physicists to take a wider view and search more generally for new particles or interactions. “Instead of zooming in, we try to look in as many places as possible in a consistent way.”

    Such a search makes room for the unexpected, she says. “You’re not dependent on the prior interpretation of something you would be looking for.”

    Theorist Patrick Fox and experimentalist Anadi Canepa, both at Fermilab, collaborate on searches for new physics.


    In Canepa’s work on the CMS experiment, the other general-purpose particle detector at the LHC, many of the searches are model-independent.

    While the nature of these searches allows them to “cast a wider net,” Fox says, “they are in some sense shallower, because they don’t manage to strongly constrain any one particular model.”

    At the same time, “by combining the results from many independent searches, we are getting closer to one dedicated search,” Canepa says. “Developing both model-dependent and model-independent searches is the approach adopted by the CMS and ATLAS experiments to fully exploit the unprecedented potential of the LHC.”

    Driven by data and powered by machine learning

    Model-dependent searches focus on a single assumption or look for evidence of a specific final state following an experimental particle collision. Model-independent searches are far broader—and how broad is largely driven by the speed at which data can be processed.

    “We have better particle detectors, and more advanced algorithms and statistical tools that are enabling us to understand searches in broader terms,” Canepa says.

    One reason model-independent searches are gaining prominence is because now there is enough data to support them. Particle detectors are recording vast quantities of information, and modern computers can run simulations faster than ever before, she says. “We are able to do model-independent searches because we are able to better understand much larger amounts of data and extreme regions of parameter and phase space.”

    Machine-learning is a key part of this processing power, Canepa says. “That’s really a change of paradigm, because it really made us make a major leap forward in terms of sensitivity [to new signals]. It really allows us to benefit from understanding the correlations that we didn’t capture in a more classical approach.”

    These broader searches are an important part of modern particle physics research, Fox says.

    “At a very basic level, our job is to bequeath to our descendants a better understanding of nature than we got from our ancestors,” he says. “One way to do that is to produce lots of information that will stand the test of time, and one way of doing that is with model-independent searches.”

    Models go in and out of fashion, he adds. “But model-independent searches don’t feel like they will.”

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 2:12 pm on March 22, 2019 Permalink | Reply
    Tags: , , CERN CMS, , Muoscope-a new small-scale portable muon telescope, , ,   

    From CERN CMS: “A ‘muoscope’ with CMS technology” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN CMS

    22 March, 2019
    Cristina Agrigoroae

    1
    The resistive plate chambers (RPC) at CMS are fast gaseous detectors that provide a muon trigger system (Image: CERN)

    Particle physicists are experts at seeing invisible things and their detecting techniques have already found many applications in medical imaging or the analysis of art works. Researchers from the CMS experiment at the Large Hadron Collider are developing a new application based on one of the experiment’s particle detectors: a new, small-scale, portable muon telescope, which will allow imaging of visually inaccessible spaces.

    CERN CMS Muoscope- a new, small-scale, portable muon telescope developed by the CMS Collaborators from Ghent University and the University of Louvain in Belgium

    Earth’s atmosphere is constantly bombarded by particles arriving from outer space. By interacting with atmospheric matter, they decay into a cascade of new particles, generating a flux of muons, heavier cousins of electrons. These cosmic-ray muons continue their journey towards the Earth’s surface, travelling through almost all material objects.

    This “superpower” of muons makes them the perfect partners for seeing through thick walls or other visually challenging subjects. Volcanic eruptions, enigmatic ancient pyramids, underground caves and tunnels: these can all be scanned and explored from the inside using muography, an imaging method using naturally occurring background radiation in the form of cosmic-ray muons.

    Large-area muon telescopes have been developed in recent years for many different applications, some of which use technology developed for the LHC detectors. The muon telescope conceived by CMS researchers from two Belgian universities, Ghent University and the Catholic University of Louvain, is compact and light and therefore easy to transport. It is nonetheless able to perform muography at high resolution. It will be the first spin-off for muography using the CMS Resistive Plate Chambers (RPC) technology. A first prototype of the telescope, also baptised a “muoscope”, has been built with four RPC planes with an active area of 16×16 cm. The same prototype was used in the “UCL to Mars” project; it was tested for its robustness in a simulation of Mars-like conditions in the Utah Desert, where it operated for one month and later came back fully functional.

    Other CMS technologies have been used in muon tomography for security and environmental protection, as well as for homeland security.

    Learn more about the muon telescope here.

    See the full article here.


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  • richardmitnick 3:26 pm on February 26, 2019 Permalink | Reply
    Tags: "What’s in store for the CMS detector over the next two years?", , CERN CMS, , , , ,   

    From CERN CMS: “What’s in store for the CMS detector over the next two years?” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN CMS

    26 February, 2019
    Letizia Diamante

    CERN/CMS Detector

    A jewel of particle physics, the CMS experiment is a 14 000-tonne detector that aims to solve a wide range of questions about the mysteries around the Higgs boson and dark matter.

    CERN CMS Higgs Event

    Now that the Large Hadron Collider (LHC) beam has been switched off for a two-year technical stop, Long Shutdown 2 (LS2), CMS is preparing for significant maintenance work and upgrades.

    1
    This diagram of the CMS detector shows some of the maintenance and upgrades in store over the next years

    All the LHC experiments at CERN want to exploit the full benefits of the accelerator’s upgrade, the High-Luminosity LHC (HL-LHC), scheduled to start in 2026.

    The HL-LHC will produce between five and ten times more collisions than the LHC, allowing more precision measurements of rare phenomena that are predicted in the Standard Model to be taken, and maybe even detecting new particles that have never been seen before. To take advantage of this, some of CMS’s components need to be replaced.

    Standard Moldel of Particle Physics

    Standard Model of Particle Physics from Symmetry Magazine

    In the heart of CMS

    Hidden inside several layers of subdetectors, the pixel detector surrounding the beam pipe is the core of the experiment, as it is the closest to the particle-collision point. During LS2, the innermost layer of the present pixel detector will be replaced, using more high-luminosity-tolerant and radiation-tolerant components. The beam pipe will also be replaced in LS2, with one that will allow the extremities of the future pixel detectors to get even closer to the interaction point. This third-generation pixel detector will be installed during the third long shutdown (LS3) in 2024–2026.

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    CMS core removal during the Long Shutdown 2 (LS2) (Image: Maximilien Brice/Julien Ordan/CERN)

    Without missing a thing

    Beyond the core, the CMS collaboration is also planning to work on the outermost part of the detector, which detects and measures muons – particles similar to electrons, but much heavier. They are preparing to install 40 large Multi-Gas Electron Multiplier (GEM) chambers to measure muons that scatter at an angle of around 10° – one of the most challenging angles for the detector to deal with. Invented in 1997 by Fabio Sauli, GEM chambers are already used in other CERN experiments, including COMPASS, TOTEM and LHCb, but the scale of CMS is far greater than the other detectors. The GEM chambers consist of a thin, metal-clad polymer foil, chemically pierced with millions of holes, typically 50 to 100 per millimetre, submerged in a gas. As muons pass through, electrons released by the gas drift into the holes, multiply in a very strong electric field and transfer to a collection region.

    Fast-forward to the future

    Some of the existing detectors would not perform well enough during the HL-LHC phase, as the number of proton–proton collisions produced in the HL-LHC will be ten times higher than that originally planned for the CMS experiment. Therefore, the high-granularity calorimeter (HGCAL) will replace the existing endcap electromagnetic and hadronic calorimeters during LS3, between 2024 and 2026. The new detector will comprise over 1000 m² of hexagonal silicon sensors and plastic scintillator tiles, distributed over 100 layers (50 in each endcap), providing unprecedented information about electrons, photons and hadrons. Exploiting this detector is a major challenge for software and analysis, and physicists and computer science experts are already working on advanced techniques, such as machine learning.

    4
    Ongoing tests on the modules of the high-granularity calorimeter (HGCAL). Intense R&D is planned for LS2 to ensure that the new detector will be ready for installation during LS3. (Image: Maximilien Brice/CERN)

    Building, building, building

    CMS has also been involved with the HL-LHC civil-engineering work, which kick-started in June 2018 and is ongoing. The project includes five new buildings on the surface at Cessy, France, as well as modifications to the underground cavern and galleries.

    CMS’s ambitious plan for the near and longer-term future is preparing the detector for more exciting undertakings. Stay tuned for more.

    Read more in “CMS has high luminosity in sight” in the latest CERN Courier, as well as LS2 highlights from ALICE, ATLAS and LHCb.

    See the full article here.


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  • richardmitnick 8:42 pm on February 15, 2019 Permalink | Reply
    Tags: , , CERN CMS, , , ,   

    From CERN CMS: “CMS gets first result using largest ever LHC data sample” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN CMS

    15 February, 2019

    The CMS collaboration at CERN has submitted its first paper based on the full LHC dataset collected in 2018 and data collected in 2016 and 2017.

    Just under three months after the final proton–proton collisions from the Large Hadron Collider (LHC)’s second run (Run 2), the CMS collaboration has submitted its first paper [Physical Review Letters] based on the full LHC dataset collected in 2018 – the largest sample ever collected at the LHC – and data collected in 2016 and 2017. The findings reflect an immense achievement, as a complex chain of data reconstruction and calibration was necessary to be able to use the data for analysis suitable for a scientific result.

    “It is truly a sign of effective scientific collaboration and the high quality of the detector, software and the CMS collaboration as a whole. I am proud and extremely impressed that the understanding of the so recently collected data is sufficiently advanced to produce this very competitive and exciting result,” said CMS spokesperson Roberto Carlin.

    Quantum chromodynamics (QCD) is one of the pillars of the Standard Model of elementary particles and describes how quarks and gluons are confined within composite particles called hadrons, of which protons and neutrons are examples.

    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.

    However, the QCD processes behind this confinement are not yet well understood, despite much progress in the last two decades. One way to understand these processes is to study the little known Bc particle family, which consists of hadrons composed of a beauty quark and a charm antiquark (or vice-versa).

    The high collision energies and rates provided by the Large Hadron Collider opened the path for the exploration of the Bc family. The first studies were published in 2014 [Physical Review Letters] by the ATLAS collaboration, using data collected during LHC’s first run. At the time, ATLAS reported the observation of a Bc particle called Bc(2S). On the other hand, the LHCb collaboration reported in 2017 that their data showed no evidence of Bc(2S) at all. Analysing the large LHC Run 2 data sample, collected in 2016, 2017 and 2018, CMS has now observed Bc(2S) as well as another Bc particle known as Bc*(2S). The collaboration has also been able to measure the mass of Bc(2S) with a good precision. These measurements provide a rich source of information on the QCD processes that bind heavy quarks into hadrons. For more information about the results visit the CMS webpage.

    The results presented at CERN this week.

    See the full article here.


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    Please help promote STEM in your local schools.

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    Meet CERN in a variety of places:

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    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

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  • richardmitnick 12:30 pm on November 1, 2018 Permalink | Reply
    Tags: , , CERN CMS, , , , , , Tantalising 'Bumps' in Large Hadron Collider Data   

    From Science Alert: “CERN’s About to Release Details on Tantalising ‘Bumps’ in Large Hadron Collider Data” 

    ScienceAlert

    From Science Alert

    1 NOV 2018
    MICHELLE STARR

    Strap yourselves in, because CERN has something up its sleeve.

    On Thursday 1 November, Large Hadron Collider (LHC) physicists will be discussing the fact that they may have found a new and unexpected new particle.

    “I’d say theorists are excited and experimentalists are very sceptical,” CERN physicist Alexandre Nikitenko told The Guardian. “As a physicist I must be very critical, but as the author of this analysis I must have some optimism too.”

    The telltale signal is a bump in the data collected by the LHC’s Compact Muon Solenoid (CMS) detector as the researchers were smashing together particles to look for something else entirely.

    CERN/CMS Detector

    When heavy particles – such as the Higgs Boson – are produced through particle collisions, they decay almost immediately. This produces a shower of smaller mass particles, as well as increased momentum, which can be picked up by the LHC’s detectors.

    CERN CMS Higgs Event


    CERN ATLAS Higgs Event

    When these particle showers produced pairs of muons (a type of elementary particle that is similar to an electron but with a much higher mass), the team sat up and paid attention. But what they traced these pairs back to was, to be very scientific about it, mega weird.

    The new and unknown particle that seems to have produced the muons has a mass of around 28 GeV (giga-electronvolts), just over a fifth of the mass of the Higgs boson (125 GeV).

    There’s nothing in any of the current models that predicts this mass.

    It’s unlikely to be physics-breaking, sorry to disappoint. But it is strange – a mass that has formed where no mass was expected.

    A word of caution, though: it’s too early to get excited.

    The signal could just be a glitch in the data, generated from random noise, which ended up being the case with what had been a tremendously exciting 750 GeV signal in 2016 – until it was found to be just a statistical fluctuation.

    Until this data has been checked against newer CMS data, as well as data from the ATLAS detector, the discovery remains unconfirmed.

    CERN/ATLAS detector

    Still, an anomalous detection is always interesting – so we’ll be tuning in tomorrow to see what the research team has to say when they give their talk.

    You can also check out their paper – which has yet to be peer-reviewed – on pre-print resource arXiv.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 1:10 pm on August 31, 2018 Permalink | Reply
    Tags: , , CERN CMS, , , Hunting for dark quarks, , ,   

    From CERN: “Hunting for dark quarks” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN

    31 Aug 2018
    Ana Lopes

    1
    A proton–proton collision event with two emerging-jet candidates. (Image: CMS/CERN)

    Quarks are the smallest particles that we know of. In fact, according to the Standard Model of particle physics, which describes all known particles and their interactions, quarks should be infinitely small.

    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.


    Standard Model of Particle Physics from Symmetry Magazine

    If that’s not mind-boggling enough, enter dark quarks – hypothetical particles that have been proposed to explain dark matter, an invisible form of matter that fills the universe and holds the Milky Way and other galaxies together.

    In a recent study, the CMS collaboration describes how it has sifted through data from the Large Hadron Collider (LHC) to try and spot dark quarks. Although the search came up empty-handed, it allowed the team to inch closer to the parent particles from which dark quarks may originate.

    One compelling theory extends the Standard Model to explain why the observed mass densities of normal matter and dark matter are similar. It does so by invoking the existence of dark quarks that interact with ordinary quarks via a mediator particle. If such mediator particles were produced in pairs in a proton–proton collision, each mediator particle of the pair would transform into a normal quark and a dark quark, both of which would produce a spray, or “jet”, of particles called hadrons, composed of quarks or dark quarks. In total, there would be two jets of regular hadrons originating from the collision point, and two “emerging” jets that would emerge a distance away from the collision point because dark hadrons would take some time to decay into visible particles.

    In their study, the CMS researchers looked through data from proton–proton collisions collected at the LHC at an energy of 13 TeV to search for instances, or “events”, in which such mediator particles and associated emerging jets might occur. They used two distinguishing features to identify emerging jets and pick them out from a background of events that are expected to mimic their traits.

    The team found no strong evidence for the existence of such emerging jets, but the data allowed them to exclude masses for the hypothetical mediator particle of 400–1250 GeV for dark pions that travel for lengths between 5 and 225 mm before they decay. The results are the first from a dedicated search for such mediator particles and jets.

    See the full article here.


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

    Stem Education Coalition

    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Grand Tunnel

    CERN LHC particles

    OTHER PROJECTS AT CERN

    CERN AEGIS

    CERN ALPHA

    CERN ALPHA

    CERN AMS

    CERN ACACUSA

    CERN ASACUSA

    CERN ATRAP

    CERN ATRAP

    CERN AWAKE

    CERN AWAKE

    CERN CAST

    CERN CAST Axion Solar Telescope

    CERN CLOUD

    CERN CLOUD

    CERN COMPASS

    CERN COMPASS

    CERN DIRAC

    CERN DIRAC

    CERN ISOLDE

    CERN ISOLDE

    CERN LHCf

    CERN LHCf

    CERN NA62

    CERN NA62

    CERN NTOF

    CERN TOTEM

    CERN UA9

    CERN Proto Dune

    CERN Proto Dune

     
  • richardmitnick 10:33 am on August 28, 2018 Permalink | Reply
    Tags: , , , CERN CMS, , Long-sought decay of Higgs boson observed, , ,   

    From CERN via phys.org: “Long-sought decay of Higgs boson observed” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN

    via

    phys.org

    August 28, 2018, CERN

    1
    A candidate event display for the production of a Higgs boson decaying to two b-quarks (blue cones), in association with a W boson decaying to a muon (red) and a neutrino. The neutrino leaves the detector unseen, and is reconstructed through the missing transverse energy (dashed line). Credit: ATLAS Collaboration/CERN

    CERN ATLAS Higgs Event


    CERN ATLAS

    Six years after its discovery, the Higgs boson has at last been observed decaying to fundamental particles known as bottom quarks. The finding, presented today at CERN1 by the ATLAS and CMS collaborations at the Large Hadron Collider (LHC), is consistent with the hypothesis that the all-pervading quantum field behind the Higgs boson also gives mass to the bottom quark. Both teams have submitted their results for publication today.

    CERN CMS Higgs Event


    CERN/CMS Detector

    The Standard Model of particle physics predicts that about 60% of the time a Higgs boson will decay to a pair of bottom quarks, the second-heaviest of the six flavours of quarks.

    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.


    Standard Model of Particle Physics from Symmetry Magazine

    Testing this prediction is crucial because the result would either lend support to the Standard Model – which is built upon the idea that the Higgs field endows quarks and other fundamental particles with mass – or rock its foundations and point to new physics.

    Spotting this common Higgs-boson decay channel is anything but easy, as the six-year period since the discovery of the boson has shown. The reason for the difficulty is that there are many other ways of producing bottom quarks in proton–proton collisions. This makes it hard to isolate the Higgs-boson decay signal from the background “noise” associated with such processes. By contrast, the less-common Higgs-boson decay channels that were observed at the time of discovery of the particle, such as the decay to a pair of photons, are much easier to extract from the background.

    To extract the signal, the ATLAS and CMS collaborations each combined data from the first and second runs of the LHC, which involved collisions at energies of 7, 8 and 13 TeV. They then applied complex analysis methods to the data. The upshot, for both ATLAS and CMS, was the detection of the decay of the Higgs boson to a pair of bottom quarks with a significance that exceeds 5 standard deviations. Furthermore, both teams measured a rate for the decay that is consistent with the Standard Model prediction, within the current precision of the measurement.

    2
    Candidate event display for the production of a Higgs boson decaying to two b-quarks. A 2 b-tag, 2-jet, 2-electron event within the signal-like portion of the high pTV and high BDTVH output distribution is shown (Run 337215, Event 1906922941). Electrons are shown as blue tracks with a large energy deposit in the electromagnetic calorimeter, corresponding to light green bars. Two of them form an invariant mass of 93.6 GeV, compatible with a Z boson. The two central high-pT b-tagged jets are represented by light blue cones. They contain the green and yellow bars corresponding to the energy deposition in the electromagnetic and hadronic calorimeters respectively, and they have an invariant mass of 128.1 GeV. The value of pTV is 246.7 GeV, and BDTVH output value is 0.47. Credit: ATLAS Collaboration/CERN

    “This observation is a milestone in the exploration of the Higgs boson. It shows that the ATLAS and CMS experiments have achieved deep understanding of their data and a control of backgrounds that surpasses expectations. ATLAS has now observed all couplings of the Higgs boson to the heavy quarks and leptons of the third generation as well as all major production modes,” said Karl Jakobs, spokesperson of the ATLAS collaboration.

    “Since the first single-experiment observation of the Higgs boson decay to tau-leptons one year ago, CMS, along with our colleagues in ATLAS, has observed the coupling of the Higgs boson to the heaviest fermions: the tau, the top quark, and now the bottom quark. The superb LHC performance and modern machine-learning techniques allowed us to achieve this result earlier than expected,” said Joel Butler, spokesperson of the CMS collaboration.

    With more data, the collaborations will improve the precision of these and other measurements and probe the decay of the Higgs boson into a pair of much-less-massive fermions called muons, always watching for deviations in the data that could point to physics beyond the Standard Model.

    3
    Candidate event display for the production of a Higgs boson decaying to two b-quarks. A 2-tag, 2-jet, 0-lepton event within the signal-like portion of the high pTV and high BDTVH output (Run 339500, Event 694513952) is shown. The ETMiss, shown as a white dashed line, has a magnitude of 479.1 GeV. The two central high-pT b-tagged jets are represented by light blue cones. They contain the green and yellow bars corresponding to the energy deposition in the electromagnetic and hadronic calorimeters respectively. The dijet invariant mass of 128.1 GeV. The BDTVH output value is 0.74. Credit: ATLAS Collaboration/CERN

    “The experiments continue to home in on the Higgs particle, which is often considered a portal to new physics. These beautiful and early achievements also underscore our plans for upgrading the LHC to substantially increase the statistics. The analysis methods have now been shown to reach the precision required for exploration of the full physics landscape, including hopefully new physics that so far hides so subtly,” said CERN Director for Research and Computing Eckhard Elsen.

    Science paper:
    Observation of Higgs boson decay to bottom quarks

    See the full article here.


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

    Stem Education Coalition

     
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