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  • richardmitnick 9:59 am on September 2, 2021 Permalink | Reply
    Tags: "The Installation of the BRIL Luminometers: Preparing for a bright Run 3", , , BRIL: "Beam Radiation Instrumentation and Luminosity", CERN CH CMS, , It is crucial to measure the real-time rate of collisions at CMS in order to optimize both the trigger rates and the quality of the beams delivered by the Large Hadron Collider (LHC)., Once in their final position the BRIL detectors lay at the heart of the CMS detector ~1.8 m from the interaction point just outside the forward pixel tracking detector., One of the most significant design changes has been the implementation of a new active cooling circuit for BCM1F which is essential for a silicon-based detector., , , , The silicon sensors used for BCM1F were sourced from a batch currently being developed for the CMS Phase II upgrade for the High-Luminosity LHC., Three instruments: the Beam Condition Monitor “Fast” (BCM1F); Beam Condition Monitor for Losses (BCM1L); Pixel Luminosity Telescope (PLT)   

    From CERN (CH) CMS: “The Installation of the BRIL Luminometers-Preparing for a bright Run 3” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    9.1.21

    By Andrés G. Delannoy and Joanna Wanczyk, for the BRIL group

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    After long months of preparations, the Beam Radiation Instrumentation and Luminosity (BRIL) group has completed the installation of three instruments dedicated to the measurement of luminosity and beam conditions: the Beam Condition Monitor “Fast” (BCM1F), the Beam Condition Monitor for Losses (BCM1L), and the Pixel Luminosity Telescope (PLT). All three of the BRIL subsystems represent a new “generation” in their respective design history. Both PLT and BCM1F implement the use of silicon sensors, while BCM1L uses poly-crystalline diamond sensors.

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    Finalized BRIL subsystems, where the PLT is enclosed in the yellow structure with BCM1F directly behind it. Two green BCM1L modules are visible for the top left quadrant. Credits: A.G. Delannoy.

    It is crucial to measure the real-time rate of collisions at CMS in order to optimize both the trigger rates and the quality of the beams delivered by the Large Hadron Collider (LHC). Moreover, continuously assessing the beam conditions is essential to the protection of the LHC machine and sensitive CMS sub-detectors. And, of course, the aggregated luminosity measurements need to be meticulously understood to determine the expected frequency of each type of interaction in nearly every analysis performed on the data collected by the CMS experiment.

    All in all, the design and production of new components, sensor characterization, assembly, stress-testing under thermal cycles troubleshooting and repairs, etc. spanned a few years of challenging work, which ramped up as the Long Shutdown 2 came to a close and the installation date lurked around the corner. Finally, after finalizing all preparations, the transport activities began before sunrise of July 5th, 2021.

    Each half of the detector was carefully loaded onto a special transport vehicle and dry air was circulated inside their transport boxes. Only days before, each quarter of the detector had been delicately readied for its journey, which included labeling them with their affectionately selected aliases: Calabrese, Capricciosa, Diavola, and Margherita. The detector slowly made its way along the base of the Jura mountains until reaching the CMS site. The transport boxes containing the BRIL subsystems are relatively small, which allowed them to ride down in the elevator to the ground floor, 97m underground, to the CMS experimental cavern where they were subsequently craned up to the bulkhead platform.

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    +Z side of the BRIL subsystems being craned onto the bulkhead platform. Credits: A.G. Delannoy.

    Once in their final position the BRIL detectors lay at the heart of the CMS detector ~1.8 m from the interaction point just outside the forward pixel tracking detector. The carbon-fiber structure that supports each detector quadrant has small wheels that guide it along purposely designed rails into its final location. After physically installing each of the detector quadrants, the cooling circuit, which provides active coolant to the PLT and BCM1F detectors, had to be tightly sealed using specialized metal o-rings.

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    Joanna Wanczyk (left) and Rob Loos (right) install the +Z Far (Margherita) quadrant. Credits: A.G. Delannoy.

    One of the most significant design changes has been the implementation of a new active cooling circuit for BCM1F which is essential for a silicon-based detector. The PLT cooling loop has been modified to include an extension for BCM1F. The design of the BCM1F cooling circuit follows the approach implemented for the PLT during Run 2: the cooling structure is fabricated by 3D printing a titanium alloy using the selective laser melting technique.

    Furthermore, the silicon sensors used for BCM1F were sourced from a batch currently being developed for the CMS Phase II upgrade for the High-Luminosity LHC. The same is the case for three of the sensors used in one of the PLT channels. “This is the first time that these prototype Phase II silicon pixel sensors will be installed in CMS, so the whole community is eager to see how this material behaves,” says Anne Dabrowski, CMS BRIL project manager.

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    Joanna Wanczyk (left) and Georg Auzinger (right) work on the -Z side bulkhead platform. Credits: A.G. Delannoy.


    BRIL Upgrade

    See the full article here.


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  • richardmitnick 1:38 pm on August 7, 2021 Permalink | Reply
    Tags: "Successful installation of the CMS Pixel Tracker", , , CERN CH CMS, , , ,   

    From CERN (CH) CMS: “Successful installation of the CMS Pixel Tracker” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    1
    The pixel tracker is the subdetector that is closest to the beamline in the CMS experiment. Image: CERN.

    After more than two years of maintenance and upgrades, the Pixel Tracker has been installed at the centre of the CMS detector and is now ready for commissioning.

    Of all the CMS subdetectors, the Pixel Tracker is the closest to the interaction point (IP) – the point of collision between the proton beams. In the core of the detector, it reconstructs the paths of high-energy electrons, muons and electrically charged hadrons, but also the decay of very short-lived particles such as those containing beauty or “b” quarks. Those decays are used, among other things, to study the differences between matter and antimatter.

    The Pixel Tracker is composed of concentric layers and rings of 1800 small silicon modules. Each of these modules contains about 66 000 individual pixels, for a total of 120 million pixels. The pixels’ tiny size (100×150 μm2) allows the trajectory of a particle passing through the detector to be precisely measured and its origin determined with a precision of about 10 μm.

    Due to its location very close to the IP, the Pixel Tracker suffers a great deal of radiation damage from particle collisions. In the innermost layer, a mere 2.9 cm away from the beam pipe, around 600 million particles pass through one square centimetre of the detector every second. Low temperatures help to protect the Pixel Tracker from this high radiation (it is kept at -20 °C), but some damage still occurs.

    To tackle this issue, the subdetector underwent extensive repairs and upgrades in the clean room where it was stored after its extraction from the cavern at the beginning of Long Shutdown 2. Its design was improved and its innermost layer replaced. The pixel detector was then reinstalled at the centre of the CMS detector and is now ready for commissioning.

    The final installation was the latest of the many achievements of the CMS Tracker group, one of the largest sub-groups of the CMS collaboration with about 600 people from over 70 institutions in 19 countries.

    Relive the event, including footage of the operations and interviews from Lea Caminada, John Conway and Erik Butz, on CERN’s social media channels:

    CERN’s YouTube channel
    CERN’s Instagram account


    CMS Pixel tracker installation 2021

    See the full article here.


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  • richardmitnick 10:27 pm on July 26, 2021 Permalink | Reply
    Tags: "Triple Treat! CMS observes production of three massive vector bosons", , , CERN CH CMS, , , ,   

    From CERN (CH) CMS: “Triple Treat! CMS observes production of three massive vector bosons” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    Recovered 7.26.21

    1
    2

    The CMS collaboration has released the first observation of the simultaneous production of three W or Z bosons in proton-proton collisions at the Large Hadron Collider (LHC). The result is based on the data collected by CMS during 2016–2018 at a collision energy of 13 TeV.

    The Standard Model of the fundamental particles describes the W and Z bosons as the mediator particles of the weak force – one of the four known fundamental forces – which is responsible for the phenomenon of radioactivity as well as an essential ingredient to our Sun’s thermonuclear process.

    It is possible for the W and Z bosons to self-interact, so W and Z bosons can create more W and Z bosons, which can manifest themselves as events with two or three massive bosons. Still, this creation is rare, so the more bosons, the less frequent they are produced. Processes with two massive bosons have been observed and measured to good precision at the LHC.

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    Figure: An event collected by the CMS experiment in 2016, where two W bosons and one Z boson were produced. One W boson decayed to a muon and its neutrino, the other to an electron and its neutrino. Neutrinos cannot be detected by the CMS experiment so are inferred from the missing transverse momentum pTmiss. The Z boson decayed to two oppositely charged muons.

    The phenomenon of three massive bosons appearing in the same event is 50 times rarer than the production of the Higgs boson, which was observed at CERN in 2012. Since weak bosons are highly unstable, they almost immediately decay to electrons, muons, taus, neutrinos or quarks – the latter forming sprays of particles, called “jets”. Besides neutrinos, all of these particles can be observed with the CMS detector, a highly sophisticated “camera” capturing snapshots of the proton-proton collisions at the LHC, but not necessarily at 100% efficiency.

    The easiest way to identify the W and Z boson is when they decay to electrons or muons. With three bosons, we expect up to six electrons or muons, something that is extremely unlikely to happen at the LHC. Since in that case only some W and Z boson decay modes can be used, only a fraction of the events containing the massive bosons can eventually be studied in the detector, making the observation even more challenging. Moreover, other events produced in proton-proton collisions tend to mimic the three massive bosons signature, making it a difficult task to tell them apart. Machine learning algorithms are deployed in the analysis to improve the performance of the lepton efficiency, and to distinguish actual tri-boson events from the background.

    After the analysis a sample of tri-boson events was isolated with a significance of 5.7 standard deviations, meaning that the chance that this observation is not real is about one in eight million. This is the first observation of heavy tri-boson production at the LHC, well above the well-established 5-sigma threshold that particle physicists use to claim a discovery. The measured number of the collisions consistent with three W or Z bosons agrees with the predictions of the Standard Model, the best current understanding of fundamental particles and their interactions.

    The observation of these extremely infrequent tri-boson events is the first step towards confirming the existence of the quartic self-interaction between the massive electroweak bosons. The result also opens up a new window to look for possible deviations from the predictions of the Standard Model, which may direct us to where to search for the existence of new particles, for example, additional Higgs bosons carrying an electric charge different than that predicted by the Standard Model.

    This first look at this rare process is only the start, and in future runs of the LHC and High-luminosity LHC will provide the data to further study the interactions between the bosons, and eventually get a more in-depth probe into establishing the underlying structure of the Standard Model.

    Science paper:
    Physical Review Letters

    See the full article here.


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  • richardmitnick 2:48 pm on April 25, 2021 Permalink | Reply
    Tags: "Search for New Physics with one charged lepton and missing energy", , , CERN CH CMS, , , ,   

    From CERN (CH) CMS: “Search for New Physics with one charged lepton and missing energy” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    4.28.21
    CMS Collaboration

    1
    Figure 1. Collision event recorded by the CMS experiment, with a balanced high energy electron and missing transverse momentum. The display shows the highest transverse mass (MT) event collected in LHC Run 2 in the electron channel. The event has MT = 3.1 TeV, and the electron energy deposit is shown in the long green bar at the top of the display. The purple line denotes the direction of the missing transverse momentum.

    Event display with an electron. This is the highest MT muon+MET event recorded by CMS in Run 2

    Experimental evidence from the last half-century has established the standard model as a foundational theory of particle physics.

    Still, it is clear that the standard model is not the final theory. There are many open questions: Is the mass of Higgs natural or fine-tuned? If natural, what new physics (symmetry) governs this? How does gravity play with the other forces? Are there more space dimensions than the familiar three? Do all forces unify at high energy? Many compelling theoretical ideas of new physics beyond the standard model have been proposed to address the open questions. Interestingly, many of these new theories have in common that they introduce new massive particles or differences in the behavior of known particles. If these new phenomena exist in the real world, LHC is best positioned to observe them.

    Such new particles could be a new charged W’ boson particle decaying into one charged lepton (electron or muon) and a neutrino in the proton-proton collision events recorded in the CMS detector. The W’ boson is usually predicted as a carbon copy of the W boson in the standard model, but it is very heavy, so it can also decay into the two heaviest quarks. In this analysis, the events where the W’ decays to a lepton and neutrino are taken into account because leptons are extremely clean signatures in the detector and give lower contributions from standard model processes that mimic this signature than the hadronic channels. The charged leptons can be accurately detected and measured in the CMS detector, whereas neutrinos are weakly interacting particles that will escape the detector without a signal. Nevertheless, their presence can be inferred by momentum conservation in the transverse plane. We sum the transverse momenta of all the detected particles in the event and assign the missing transverse momentum (generally called MET) to the neutrinos.

    To separate the W’ signal events from the standard model background events, CMS physicists select events with specific properties: the charged lepton and neutrino must be very energetic, the ratio of their energies has to be almost one, and they have to be back-to-back in the plane perpendicular to the beam axis. The event displays of the observed event for electron and muon channels are shown in Figure 1 and 2. One of the main tasks in this analysis is calibrating, identifying, and correctly measuring the most energetic electrons and muons ever detected in a collider experiment. For the invisible neutrino, as stated above, we can only estimate its transverse component so that the mass of the parent particle can be constrained by the transverse mass (MT). This quantity is a key one in this new physics search that distinguishes the standard model W from the new massive W’ one. Assume W’ exists and promptly decayed into two particles. In that case, the signal will be appearing as a peak (called a resonance) at the very high MT tail region, where background events hardly exist making the resonance relatively easy to spot.

    An example of the transverse mass distributions we observed is shown in Figure 3. The experimental data agree well with the standard model expectation, and there is no hint of significant deviation.

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    Figure 2: Collision event recorded by the CMS experiment, with a balanced high energy muon and missing transverse momentum. The display shows the highest transverse mass (MT) event collected in LHC Run 2 in the muon channel. The event has MT = 2.9 TeV, and the muon is shown as a red line. The purple line denotes the direction of the missing transverse momentum.

    With these data, it is possible to do two different kinds of search. Figure 3 illustrates the two scenarios: on one side, we assume the new hypothetical W’ particle can be produced at the LHC, and we look for it in our data. This is called a “direct resonance search”, as the resonance from the particle should be directly visible in the data. But the new particle might be very massive and not directly reachable with the current LHC energy. In that case, we might be able to see some hints of it, as explained in Figure 4. This is the “indirect search” and it places restrictions on how far this new physics could lie.

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    Figure 3. Transverse mass distribution for events with one energetic lepton (muon) and considerable missing transverse momentum. Shown are the observed data (black dots), the predicted standard model background contributions (colored blocks), and signals with two specific Sequential Standard Model W’ masses of 3.8 TeV (purple line) and 5.6 TeV (green line). The lower panels show the difference between the observed data and the background estimate.

    As the data agrees with what we expect, we can set limits on the new particle’s properties. These results can also be used to constrain a variety of other new physics models predicting a lepton and a neutrino in the final state. This approach (called reinterpretation) tests a host of different physics predictions like the existence of new spatial dimensions, new symmetries in nature, and more. We have also combined all of these interpretations of the data to look for a different effect of new physics: the hypothesis that the Higgs boson we discovered is not an elementary particle but is made of other undiscovered particles. This is known as the Composite Higgs scenario. With this analysis, we can explore this model in a complementary approach to looking at Higgs bosons.

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    Figure 4. Sketch showing two kinds of possibilities studied in this analysis. The new particles are at reach at the LHC (direct search), or they are very massive and beyond LHC energy, but they still change the distributions slightly (indirect search).

    It is fascinating to explore an unprecedented region for new particles. As the center-of-mass energy and the amount of accumulated data increases, more signal-like higher MT events can be observed at LHC. This will improve sensitivity for the discovery of the W’ boson if it is slightly too heavy to be seen up to now.

    A new LHC era will soon begin with Run3 (2022-2024) which plans to double the amount of data collected during Run2 (2016-2018). Furthermore, High-Luminosity LHC is scheduled to come into operation at the end of 2027 after upgrading all of the equipment (2025-2027). High-Luminosity LHC will enable us to investigate up to 20 times more data than Run2. With these data, we can test the vast scope of many new theoretical physics models much more effectively. This will lead us towards a deeper understanding of our universe and hopefully unlock many mysteries.

    See the full article here.


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  • richardmitnick 10:09 am on March 14, 2021 Permalink | Reply
    Tags: "Searching for elusive supersymmetric particles", , , CERN CH CMS, , , , , ,   

    From UC Riverside(US): “Searching for elusive supersymmetric particles” 

    UC Riverside bloc

    From UC Riverside(US)

    March 10, 2021
    Iqbal Pittalwala
    Senior Public Information Officer
    (951) 827-6050
    iqbal.pittalwala@ucr.edu

    1
    CMS. Credit: CERN


    European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire(CH)

    The Standard Model of particle physics is the best explanation to date for how the universe works at the subnuclear level and has helped explain, correctly, the elementary particles and forces between them.

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

    But the model is incomplete, requiring “extensions” to address its shortfalls.

    Owen Long, a professor of physics and astronomy at the University of California, Riverside, is a key member of an international team of scientists that has explored supersymmetry, or SUSY, as an extension of the Standard Model.

    He is also a member of the Compact Muon Solenoid, or CMS, Collaboration at the Large Hadron Collider at CERN in Geneva. CMS is one of CERN’s large particle-capturing detectors.

    “The data from our CMS experiments do not allow us to claim we have found SUSY,” Long said. “But in science, not finding something — a null result — can also be exciting.”

    A theory of physics beyond the Standard Model, SUSY refers to the symmetry between two kinds of elementary particles, bosons and fermions, and is tied to their spins. SUSY proposes that all known fundamental particles have heavier, supersymmetric counterparts, with each supersymmetric partner differing from its Standard Model counterpart by one-half unit in spin. This doubles the number of particle types in nature, allowing many new interactions between the regular particles and new SUSY particles.

    “This is a big change to the Standard Model,” Long said. “The extension can provide answers to some of the fundamental questions that are still unanswered, such as: What is dark matter?”

    The Standard Model explains neither gravity nor dark matter. But in the case of the latter, SUSY does offer a candidate in the form of the lightest supersymmetric particle, which is stable, electrically neutral, and weakly interacting. The invocation of SUSY also naturally explains the small mass of the Higgs boson.

    “The discovery of the elusive SUSY particles would provide an extraordinary insight into the nature of reality,” Long said. “And it would be a revolutionary moment in physics for experimentalists and theorists.”

    At CMS, Long and other scientists hoped to find evidence for SUSY particles by examining signs of their decay as measured by an energy imbalance called missing transverse energy. When they examined the data, they found no signs of the expected energy imbalance from producing SUSY particles.

    “We, therefore, have no evidence for SUSY,” Long said. “But perhaps SUSY is there, and it is just more hidden than initially thought. It’s true we did not find something new, which is disappointing. But it is still very important scientific progress. We now know a lot more about where SUSY does not exist. Our null result motivates us to do follow-up work and guides us where to look next.”

    Long explained that he and his fellow scientists have been looking for SUSY for a long time through a technique based on a connection to dark matter.

    “Those efforts did not find SUSY particles,” he said. “Our new result involves a completely different approach, developed over a couple of years and driven by our interest in looking for SUSY in novel ways. While we found no evidence for SUSY, there is still interest in exploring the idea that SUSY could exist in ways that are more difficult to find. We already have preliminary measurements we are working on.”

    Long was funded by a grant from the Department of Energy. He was joined by three other senior scientists from other institutions in the research.

    UCR is a founding member of the CMS experiment — one of only five U.S. institutions with that distinction.

    Science paper:
    Search for top squarks in final states with two top quarks and several light-flavor jets in proton-proton collisions at s√= 13 TeV.
    Physical Review D

    See the full article here .

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    UC Riverside Campus

    The University of California, Riverside(US) is a public land-grant research university in Riverside, California. It is one of the 10 campuses of the University of California(US) system. The main campus sits on 1,900 acres (769 ha) in a suburban district of Riverside with a branch campus of 20 acres (8 ha) in Palm Desert. In 1907, the predecessor to UC Riverside was founded as the UC Citrus Experiment Station, Riverside which pioneered research in biological pest control and the use of growth regulators responsible for extending the citrus growing season in California from four to nine months. Some of the world’s most important research collections on citrus diversity and entomology, as well as science fiction and photography, are located at Riverside.

    UC Riverside’s undergraduate College of Letters and Science opened in 1954. The Regents of the University of California declared UC Riverside a general campus of the system in 1959, and graduate students were admitted in 1961. To accommodate an enrollment of 21,000 students by 2015, more than $730 million has been invested in new construction projects since 1999. Preliminary accreditation of the UC Riverside School of Medicine was granted in October 2012 and the first class of 50 students was enrolled in August 2013. It is the first new research-based public medical school in 40 years.

    UC Riverside is classified among “R1: Doctoral Universities – Very high research activity.” The 2019 U.S. News & World Report Best Colleges rankings places UC Riverside tied for 35th among top public universities and ranks 85th nationwide. Over 27 of UC Riverside’s academic programs, including the Graduate School of Education and the Bourns College of Engineering, are highly ranked nationally based on peer assessment, student selectivity, financial resources, and other factors. Washington Monthly ranked UC Riverside 2nd in the United States in terms of social mobility, research and community service, while U.S. News ranks UC Riverside as the fifth most ethnically diverse and, by the number of undergraduates receiving Pell Grants (42 percent), the 15th most economically diverse student body in the nation. Over 70% of all UC Riverside students graduate within six years without regard to economic disparity. UC Riverside’s extensive outreach and retention programs have contributed to its reputation as a “university of choice” for minority students. In 2005, UCR became the first public university campus in the nation to offer a gender-neutral housing option.UC Riverside’s sports teams are known as the Highlanders and play in the Big West Conference of the National Collegiate Athletic Association (NCAA) Division I. Their nickname was inspired by the high altitude of the campus, which lies on the foothills of Box Springs Mountain. The UC Riverside women’s basketball team won back-to-back Big West championships in 2006 and 2007. In 2007, the men’s baseball team won its first conference championship and advanced to the regionals for the second time since the university moved to Division I in 2001.

    History

    At the turn of the 20th century, Southern California was a major producer of citrus, the region’s primary agricultural export. The industry developed from the country’s first navel orange trees, planted in Riverside in 1873. Lobbied by the citrus industry, the UC Regents established the UC Citrus Experiment Station (CES) on February 14, 1907, on 23 acres (9 ha) of land on the east slope of Mount Rubidoux in Riverside. The station conducted experiments in fertilization, irrigation and crop improvement. In 1917, the station was moved to a larger site, 475 acres (192 ha) near Box Springs Mountain.

    The 1944 passage of the GI Bill during World War II set in motion a rise in college enrollments that necessitated an expansion of the state university system in California. A local group of citrus growers and civic leaders, including many UC Berkeley(US) alumni, lobbied aggressively for a UC-administered liberal arts college next to the CES. State Senator Nelson S. Dilworth authored Senate Bill 512 (1949) which former Assemblyman Philip L. Boyd and Assemblyman John Babbage (both of Riverside) were instrumental in shepherding through the State Legislature. Governor Earl Warren signed the bill in 1949, allocating $2 million for initial campus construction.

    Gordon S. Watkins, dean of the College of Letters and Science at University of California at Los Angeles(US), became the first provost of the new college at Riverside. Initially conceived of as a small college devoted to the liberal arts, he ordered the campus built for a maximum of 1,500 students and recruited many young junior faculty to fill teaching positions. He presided at its opening with 65 faculty and 127 students on February 14, 1954, remarking, “Never have so few been taught by so many.”

    UC Riverside’s enrollment exceeded 1,000 students by the time Clark Kerr became president of the University of California(US) system in 1958. Anticipating a “tidal wave” in enrollment growth required by the baby boom generation, Kerr developed the California Master Plan for Higher Education and the Regents designated Riverside a general university campus in 1959. UC Riverside’s first chancellor, Herman Theodore Spieth, oversaw the beginnings of the school’s transition to a full university and its expansion to a capacity of 5,000 students. UC Riverside’s second chancellor, Ivan Hinderaker led the campus through the era of the free speech movement and kept student protests peaceful in Riverside. According to a 1998 interview with Hinderaker, the city of Riverside received negative press coverage for smog after the mayor asked Governor Ronald Reagan to declare the South Coast Air Basin a disaster area in 1971; subsequent student enrollment declined by up to 25% through 1979. Hinderaker’s development of innovative programs in business administration and biomedical sciences created incentive for enough students to enroll at Riverside to keep the campus open.

    In the 1990s, the UC Riverside experienced a new surge of enrollment applications, now known as “Tidal Wave II”. The Regents targeted UC Riverside for an annual growth rate of 6.3%, the fastest in the UC system, and anticipated 19,900 students at UC Riverside by 2010. By 1995, African American, American Indian, and Latino student enrollments accounted for 30% of the UC Riverside student body, the highest proportion of any UC campus at the time. The 1997 implementation of Proposition 209—which banned the use of affirmative action by state agencies—reduced the ethnic diversity at the more selective UC campuses but further increased it at UC Riverside.

    With UC Riverside scheduled for dramatic population growth, efforts have been made to increase its popular and academic recognition. The students voted for a fee increase to move UC Riverside athletics into NCAA Division I standing in 1998. In the 1990s, proposals were made to establish a law school, a medical school, and a school of public policy at UC Riverside, with the UC Riverside School of Medicine and the School of Public Policy becoming reality in 2012. In June 2006, UC Riverside received its largest gift, 15.5 million from two local couples, in trust towards building its medical school. The Regents formally approved UC Riverside’s medical school proposal in 2006. Upon its completion in 2013, it was the first new medical school built in California in 40 years.

    Academics

    As a campus of the University of California(US) system, UC Riverside is governed by a Board of Regents and administered by a president. The current president is Michael V. Drake, and the current chancellor of the university is Kim A. Wilcox. UC Riverside’s academic policies are set by its Academic Senate, a legislative body composed of all UC Riverside faculty members.

    UC Riverside is organized into three academic colleges, two professional schools, and two graduate schools. UC Riverside’s liberal arts college, the College of Humanities, Arts and Social Sciences, was founded in 1954, and began accepting graduate students in 1960. The College of Natural and Agricultural Sciences, founded in 1960, incorporated the CES as part of the first research-oriented institution at UC Riverside; it eventually also incorporated the natural science departments formerly associated with the liberal arts college to form its present structure in 1974. UC Riverside’s newest academic unit, the Bourns College of Engineering, was founded in 1989. Comprising the professional schools are the Graduate School of Education, founded in 1968, and the UCR School of Business, founded in 1970. These units collectively provide 81 majors and 52 minors, 48 master’s degree programs, and 42 Doctor of Philosophy (PhD) programs. UC Riverside is the only UC campus to offer undergraduate degrees in creative writing and public policy and one of three UCs (along with Berkeley and Irvine) to offer an undergraduate degree in business administration. Through its Division of Biomedical Sciences, founded in 1974, UC Riverside offers the Thomas Haider medical degree program in collaboration with UCLA.[29] UC Riverside’s doctoral program in the emerging field of dance theory, founded in 1992, was the first program of its kind in the United States, and UC Riverside’s minor in lesbian, gay and bisexual studies, established in 1996, was the first undergraduate program of its kind in the UC system. A new BA program in bagpipes was inaugurated in 2007.

    Research and economic impact

    UC Riverside operated under a $727 million budget in fiscal year 2014–15. The state government provided $214 million, student fees accounted for $224 million and $100 million came from contracts and grants. Private support and other sources accounted for the remaining $189 million. Overall, monies spent at UC Riverside have an economic impact of nearly $1 billion in California. UC Riverside research expenditure in FY 2018 totaled $167.8 million. Total research expenditures at UC Riverside are significantly concentrated in agricultural science, accounting for 53% of total research expenditures spent by the university in 2002. Top research centers by expenditure, as measured in 2002, include the Agricultural Experiment Station; the Center for Environmental Research and Technology; the Center for Bibliographical Studies; the Air Pollution Research Center; and the Institute of Geophysics and Planetary Physics.

    Throughout UC Riverside’s history, researchers have developed more than 40 new citrus varieties and invented new techniques to help the $960 million-a-year California citrus industry fight pests and diseases. In 1927, entomologists at the CES introduced two wasps from Australia as natural enemies of a major citrus pest, the citrophilus mealybug, saving growers in Orange County $1 million in annual losses. This event was pivotal in establishing biological control as a practical means of reducing pest populations. In 1963, plant physiologist Charles Coggins proved that application of gibberellic acid allows fruit to remain on citrus trees for extended periods. The ultimate result of his work, which continued through the 1980s, was the extension of the citrus-growing season in California from four to nine months. In 1980, UC Riverside released the Oroblanco grapefruit, its first patented citrus variety. Since then, the citrus breeding program has released other varieties such as the Melogold grapefruit, the Gold Nugget mandarin (or tangerine), and others that have yet to be given trademark names.

    To assist entrepreneurs in developing new products, UC Riverside is a primary partner in the Riverside Regional Technology Park, which includes the City of Riverside and the County of Riverside. It also administers six reserves of the University of California Natural Reserve System. UC Riverside recently announced a partnership with China Agricultural University[中国农业大学](CN) to launch a new center in Beijing, which will study ways to respond to the country’s growing environmental issues. UC Riverside can also boast the birthplace of two name reactions in organic chemistry, the Castro-Stephens coupling and the Midland Alpine Borane Reduction.

     
  • richardmitnick 2:11 pm on January 12, 2021 Permalink | Reply
    Tags: "CMS collaboration releases its first open data from heavy-ion collisions", , , CERN CH CMS, , , ,   

    From CERN (CH) CMS: “CMS collaboration releases its first open data from heavy-ion collisions” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    12 January, 2021
    Achintya Rao

    CMS data recorded in 2010 and 2011 from lead–lead collisions at the Large Hadron Collider have been released into the public domain for the first time.

    1
    A heavy-ion collision recorded by CMS in 2011. Credi:Tom McCauley/CMS/CERN.

    For a few weeks each year of operation, instead of colliding protons, the Large Hadron Collider (LHC) collides nuclei of heavy elements (“heavy ions”). These heavy-ion collisions allow researchers to recreate in the laboratory conditions that existed in the very early universe, such as the soup-like state of free quarks and gluons known as the quark–gluon plasma. Now, for the first time, the Compact Muon Solenoid (CMS) collaboration at CERN is making its heavy-ion data publicly available via the CERN Open Data portal.

    Over 200 terabytes (TB) of data were released in December, from collisions that occurred in 2010 and 2011, when the LHC collided bunches of lead nuclei. Using these data, CMS had observed several signatures of the quark–gluon plasma, including the imbalance between the momenta of each jet of particles produced in a pair, the suppression (“quenching”) of particle jets in jet–photon pairs and the “melting” of certain composite particles. In addition to lead–lead collision data (two data sets from 2010 and four from 2011), CMS has also provided eight sets of reference data from proton–proton collisions recorded at the same energy.

    The open data are available in the same high-quality format that was used by the CMS scientists to publish their research papers. The data are accompanied by the software that is needed to analyse them and by analysis examples. Previous releases of CMS open data have been used not only in education but also to perform novel research. CMS is hopeful that communities of professional researchers and amateur enthusiasts as well as educators and students at all levels will put the heavy-ion data to similar use.

    “Our aim with releasing CMS data into the public domain via the Creative Commons CC0 waiver is to preserve our data and the knowledge needed to use them, in order to facilitate the widest possible use of our data,” says Kati Lassila-Perini, who has led the CMS open-data project since its inception in 2012. “We hope that those outside CMS will find these data as fascinating and valuable as we do.”

    CMS has committed to releasing 100% of the data recorded each year after an embargo period of ten years, with up to 50% of the data being made available in the interim. The embargo allows the researchers who built and operate the CMS detector adequate time to analyse the data they collect. With this release, all of the research data recorded by CMS during LHC operation in 2010 and 2011 is now in the public domain, available for anyone to study.

    You can read more about the release on the CERN Open Data portal: opendata.cern.ch/docs/cms-releases-heavy-ion-data.

    See the full article here.


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    Please help promote STEM in your local schools.

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  • richardmitnick 1:22 pm on December 18, 2020 Permalink | Reply
    Tags: "Researchers set new bounds on the mass of leptoquarks", , , , CERN CH CMS, , , ,   

    From CERN (CH) via phys.org: “Researchers set new bounds on the mass of leptoquarks” 

    Cern New Bloc

    Cern New Particle Event


    From CERN (CH)

    via


    From phys.org

    December 18, 2020

    1
    The CMS detector Credit: CERN.

    2
    The hunt for leptoquarks is on. Credit: CERN.

    At the most fundamental level, matter is made up of two types of particles: leptons, such as the electron, and quarks, which combine to form protons, neutrons and other composite particles. Under the Standard Model of particle physics [below], both leptons and quarks fall into three generations of increasing mass. Otherwise, the two kinds of particles are distinct. But some theories that extend the Standard Model predict the existence of new particles called leptoquarks that would unify quarks and leptons by interacting with both.

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

    In a new paper [Search for singly and pair-produced leptoquarks coupling to third-generation fermions in proton-proton collisions at s√= 13 TeV], the CMS collaboration reports the results of its latest search for leptoquarks that would interact with third-generation quarks and leptons (the top and bottom quarks, the tau lepton and the tau neutrino). Such third-generation leptoquarks are a possible explanation for an array of tensions with the Standard Model (or “anomalies”), which have been seen in certain transformations of particles called B mesons but have yet to be confirmed. There is therefore an additional reason for hunting down these hypothetical particles.

    The CMS team looked for third-generation leptoquarks in a data sample of proton–proton collisions that were produced by the Large Hadron Collider (LHC) at an energy of 13 TeV and were recorded by the CMS experiment between 2016 and 2018. Specifically, the team looked for pairs of leptoquarks that transform into a top or bottom quark and a tau lepton or tau neutrino, as well as for single leptoquarks that are produced together with a tau neutrino and transform into a top quark and a tau lepton.

    The CMS researchers didn’t find any indication that such leptoquarks were produced in the collisions. However, they were able to set lower bounds on their mass: they found that such leptoquarks would need to be at least 0.98–1.73 TeV in mass, depending on their intrinsic spin and the strength of their interaction with a quark and a lepton. These bounds are some of the tightest yet on third-generation leptoquarks, and they allow part of the leptoquark-mass range that could explain the B-meson anomalies to be excluded.

    The search for leptoquarks continues.

    See the full article here.


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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
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Maximilien Brice and Julien Marius Ordan.


    SixTRack CERN LHC particles

     
  • richardmitnick 2:31 pm on December 7, 2020 Permalink | Reply
    Tags: "Triple threat- The first observation of three massive gauge bosons produced in proton-proton collisions", , , CERN CH CMS, , , , ,   

    From CERN (CH) CMS via phys.org: “Triple threat- The first observation of three massive gauge bosons produced in proton-proton collisions” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN (CH) CMS

    via


    phys.org

    1
    Display of proton-proton collision events recorded by the CMS experiment. A candidate event of simultaneous production of W+, two Z bosons, with multiple electrons and muons (i.e., 5 electrons in this case). Credit: CMS Collaboration.

    The Standard Model, the most exhaustive existing theory outlining fundamental particle interactions, predicts the existence of what are known as triboson interactions.

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

    These interactions are processes in which three-gauge bosons are simultaneously produced from one Large Hadron Collider event.

    Triboson interactions are incredibly rare, often up to hundreds of times rarer than Higgs boson events, as they typically take place once every 100 billion proton-proton collisions. Although the Standard Model predicts their existence, physicists had so far been unable to observe them experimentally.

    The CMS Collaboration, a large group of researchers from numerous physics institutes worldwide have recently observed the production of three massive gauge bosons in proton-proton collisions for the first time ever. Their paper, published in Physical Review Letters, offers the first experimental evidence of the existence of triboson interactions, opening up new possibilities for the study the interactions between fundamental massive gauge bosons, namely the W±, Z, and Higgs boson.

    “The rarity and the novelty of triboson interactions was the main guiding force behind our decision to embark on a search for these events,” Saptaparna Bhattacharya, post-doctoral research associate at Northwestern University and distinguished Researcher at the LHC Physics Center at Fermilab, told Phys.org. “Our achievement is a culmination of previous attempts to look for these processes by both the ATLAS and CMS collaborations at center of mass energies of 8 and 13 TeV.”

    The CMS experiment is an ongoing research effort based on the use of a general-purpose detector at the LHC (i.e., the Compact Muon Solenoid or CMS). Over the past few years, Bhattacharya and the rest of the CMS Collaboration used this detector to gather data related to particle interactions, which could aid the search for dark matter and facilitate the discovery of new physics.

    In their recent study, the researchers examined a large dataset compiled using the detector between 2016 and 2018, as they realized that triboson interactions are becoming more accessible and have event rates large enough to be discerned from background signals. They thus set out to search for tribosons or VVV (i.e., where V=W+, W-, Z bosons) and establish the existence of triboson interactons at 5.7 standard deviations, which implies that the probability of the observation being a fluctuation of the background is one in 106, or one in 1 million.

    “While the majority of triboson decay modes involve hadronic jets, a subset of events that give rise to electrons and muons (collectively known as leptons) lead to distinctive signatures in the detector,” Bhattacharya explained. “The CMS detector is the best-known instrument for detecting leptons and we took advantage of this feature to isolate the rare VVV events from background processes.”

    The probability that large bosons will be produced in proton-proton collisions is greater at a center of mass energy of 13 TeV, compared to lower center-of-mass energies assessed in past studies. Using optimal signal selection requirements, the researchers were thus able to isolate the rare triboson process from backgrounds signals in the 2016-2018 CMS dataset.

    “The presence of the W± and Z bosons produced in proton-proton collisions can be inferred by detecting their decay products,” Philip Chang, post-doctoral researcher at University of California San Diego and part of the CMS Collaboration, told Phys.org. “One of the clearest signs of their presence is the detection of high-momentum electrons and muons. Since the process we wanted to detect involves three massive gauge bosons, multiple electrons and muons should be present as the event takes place, while in other background events that do not produce multiple massive-gauge bosons, the number of electrons and muons is low. We thus looked for proton-proton collision events with multiple electrons and muons to observe the very rare signal process from background events.”

    In the data they analyzed, Bhattacharya, Chang and the rest of the CMS Collaboration clearly identified the production of three massive gauge bosons in a proton-proton collision. Their findings are a significant contribution to the field of particle physics, as they introduce new possibilities for studying interactions between massive gauge bosons. In the future, this study could help to improve the current understanding of different types of large bosons, including the recently discovered Higgs boson.

    “The observation of the production of three heavy gauge bosons in one LHC collision constitutes a major milestone in LHC physics,” Bhattacharya explained. “At the outset, we were skeptical about discovering these processes at such an early stage of the LHC program. This discovery sheds light on the fundamental interaction between gauge bosons and opens a new window into the intricate details of the Standard Model.”

    The CMS Collaboration now plans to conduct further studies exploring the process they detected, as well as expanding their analysis to also search for events with W±, and Z boson decays to quarks and neutrinos. This will allow them to test the validity of the Standard Model further and potentially unveil new physical phenomena that cannot be explained by existing physics theories.

    “We are currently studying triboson interactions in detail, having established their existence,” Chang said. “One of the major goals of our next paper will be to scrutinize the newly discovered triboson processes and search for telltale signs of physics beyond what is predicted by the Standard Model.”

    See the full article here.


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    Please help promote STEM in your local schools.

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    Meet CERN (CH) in a variety of places:

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  • richardmitnick 12:11 pm on October 9, 2020 Permalink | Reply
    Tags: "CMS sees evidence of top quarks in collisions between heavy nuclei", , CERN CH CMS, , , ,   

    From CERN CH CMS: “CMS sees evidence of top quarks in collisions between heavy nuclei” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN CH CMS

    9 October, 2020
    Ana Lopes

    The result opens the path to study in a new and unique way the extreme state of matter that is thought to have existed shortly after the Big Bang.

    A new result by the CMS collaboration accepted by the journal Physical Review Letters demonstrates for the first time that top quarks are produced in nucleus-nucleus collisions. At the same time, this also demonstrates the capability of the CMS experiment to perform top quark studies in this unusual and challenging environment, something that very few people would have bet on until a few years ago.

    To provide the context for this breakthrough, let us recall that the flagship accelerator of CERN is named the Large Hadron Collider (LHC) and not the Large Proton Collider. This is despite how the LHC’s record-energy proton-proton collisions brought the discovery of the Higgs boson, and a vast program of searches for physics beyond the Standard Model. In a typical year of LHC operation, one out of seven months of collisions is devoted to heavy-ion beams. While proton-proton collisions are, for example, used to precisely pin down the properties of the Higgs boson and the top quark, heavy-ion collisions are used to investigate strongly-interacting matter at extreme energy densities. In particular, they are used to study quark-gluon plasma, an extreme state of matter that filled the Universe in its first microseconds of life. Studies into quark-gluon plasma are the realm of ALICE, a dedicated experiment at the LHC. However, unlike CMS or ATLAS, ALICE was never expected to be able to select top quarks.

    With a mass at around 170 times that of the proton, the top (t) quark is the heaviest known elementary particle (see Figure 1). It is also a unique and potentially very powerful tool to understand the inner content of nuclear matter.

    1
    Figure 1: Masses of the massive vector and scalar bosons (green squares), quarks (orange circles), and charged leptons (blue diamonds). This figure includes all the elementary particles whose masses have been measured to be non zero.

    The creation of a particle-antiparticle pair of such a massive quark requires for a large amount of kinetic energy to be converted into mass through a single, elementary interaction. Quarks (q) and gluons (g) inside protons and neutrons have a very large spread in energy. Therefore, only a tiny fraction of their collisions pass the threshold energy required for top quark production to occur. This means that, by selecting events containing top quarks, one is implicitly studying only the most energetic elementary collisions. As a consequence of the Heisenberg principle, these collisions probe the smallest space-time distances.

    The top quark’s large mass also results in it decaying faster than any other known quark. While the average lifetime of a top quark is of the order of a yoctosecond (0.000000000000000000000001 s or 10^-24 s), the lifetime of its sibling, the bottom (b) quark, is of the order of a picosecond (10-12 s). This matters because a yoctosecond is still hundreds of times shorter than the time required for quantum chromodynamic (QCD) processes to take place. These QCD processes include hadronisation, which “dresses” all other quarks until the final state only contains colour-neutral particles, where colour is the QCD equivalent of charge. Additional examples are the formation, expansion and cooling of the quark-gluon plasma, which are each estimated to require a timescale of the order of 10^-22 s. Therefore, unlike the other quarks, the top quark decays before such processes can occur. It can also decay within the quark-gluon plasma itself. This decay produces other quarks that experience intense interaction with the quark-gluon plasma, as shown in Figure 2.

    2
    Figure 2: Top quarks almost always decay into a b quark and W boson; the latter further decays into leptons or quarks that can be detected and form the so-called “final state”. The sketch illustrates the process of the top quark decaying to other particles, and the average decay times of each particle are indicated on the x-axis. The quark-gluon plasma density evolution (y-axis) is illustrated as a function of time.

    From the above reasons, top quarks can provide insights into the highest energy collisions. They also enable us to study how the quarks produced from top quark decay experience a “quench” in their energies through interactions with quark-gluon plasma. However, such studies are easier said than done. Heavy-ion collisions produce a huge number of particles, putting even the very advanced particle reconstruction algorithms of CMS under stress. Indeed, CMS is a multipurpose experiment, mostly optimized for high-energy proton-proton collisions. Therefore it would be unfair to expect it to be equally performant using heavy ion data but, to interpret this, the CMS experiment uses re-optimized software.

    It took years to build confidence that it was even possible for the CMS experiment to find top quarks in lead-lead collisions. A crucial milestone was the first observation of top quark production in proton-lead collisions using data taken in 2016 [Physical Review Letters]. As a lead atom is composed of 208 “nucleons” (protons or neutrons), a proton-lead collision provides 208 times more opportunities for quarks and gluons to collide, with respect to a proton-proton collision. Consequently, this results in a higher number of particles in the final state. But the problem of top quark identification in lead-lead collisions was still a tougher nut to crack: although the probability to produce a top quark is a factor of (208)x(208), or approximately 40,000, larger in a Pb-Pb collision than in a p-p one, the corresponding backgrounds are also similarly enhanced. Most importantly, the amount of data collected in a typical Pb-Pb run is orders of magnitude smaller than in p-p collisions, and the energies of the collisions between their elementary components are also smaller, leading to much fewer signal events.

    1
    Figure 3: A lead-lead collision event interpreted as containing the decay products of a top quark and a top antiquark.(Image: CERN)

    Figure 3 shows an example of how a top quark event is produced in a busy environment after a head-on, lead-lead collision. This event was recorded by the CMS experiment in late 2018. The number of extra particles is overwhelming, but there are recognisable features that indicate top quark production: a very energetic electron (green) leaving a large deposit in the electromagnetic calorimeter, a very energetic muon detected by the muon detectors (red), and two very energetic hadronic jets (orange) containing signs of originating from the hadronisation of b quarks (hence passing a so-called “b tagging” algorithm).

    Being produced in almost 100% of the top quark decays, b quarks are a crucial signature of top quark presence. On the other hand, as mentioned above, b quarks interact with quark-gluon plasma, potentially biasing the results. Thus, the quark-gluon plasma itself must be better understood before such results can be correctly interpreted.

    To achieve this, two complementary analyses were performed. One was based entirely on the features of the two leptons observed in the event, intentionally ignoring any information related to the hadronic jets in order to stay away from such subtleties. However in the second analysis, the presence of b-tagged jets was also exploited, with extra uncertainties considered in the final fit to the data. In both cases two light, charged leptons (i.e., electrons or muons) were selected, with charges opposite in sign. Also in both cases, a machine learning algorithm (a boosted decision tree, or BDT) was used to distinguish between events that were more likely to be the desired top quark production process, known as the signal process, and those that are less likely to be the desired process, known as background processes.

    Events containing an electron and a muon in their final states were grouped depending on the number of b-tagged jets they contained (0, 1 or 2). Then, for the events in each group, results from the machine learning algorithm were compared to the best-fit signal and background expectation. This is shown in Figure 4.

    4
    Figure 4: The number of events in data, the estimated numbers of events in the top quark pair signal and background processes and the total uncertainty.

    The two analyses yield results consistent with each other and with theory expectations. Results are also consistent with extrapolations from previous measurements of the tt̄ cross section in proton-proton collisions, at the same center-of-mass energy per nucleon (see Figure 5). If no top quarks were produced in lead-lead collisions, there would be a probability of 0.003% (or four sigma) that the signal would arise from a background fluctuation.

    5
    Figure 5: Results of the cross section measurements from the two alternative analyses (with and without exploiting the b-tagged jets). To compare the new results, a reference measurement from proton-proton collisions was corrected for the number of protons and neutrons in the lead nucleus. The expectation from theory calculations is also shown.

    This new measurement is not the end of the story, but is rather the beginning. With more data and ingenuity, CMS members could embark on an even more challenging decay channel, in which one W boson decays into two leptons (as in Figure 2) and the other into two quarks, which in turn decay into hadrons. Reducing the number of background events in that channel would be more difficult, but it would pay off in terms of using LHC data to increase our understanding of the interactions between quarks and the quark-gluon plasma. For example, deviations in the measured invariant mass distribution of the two quarks from the well-known W boson mass could be determined, which could be used to indirectly measure the effect of the quark-gluon plasma on the propagation of quarks. Such a measurement would complement already established techniques. With even more data, this measurement could be performed in different ranges of the top quark momentum. This is, in turn, correlated with the time it takes to go from the formation of top quarks to the presence of stable hadrons. This could provide physicists a unique window on two, big open questions in fundamental physics: how much time does the quark-gluon plasma take to form, and how long does it take to cool down?

    See the full article here.


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