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  • richardmitnick 10:15 am on January 6, 2022 Permalink | Reply
    Tags: , ALICE at CERN (CH), ALICE’s inner Gas Electron Multiplier (GEM) TPC chambers, , , , , , , RHIG: Relativistic Heavy Ion Group,   

    From Wright Laboratory at Yale University (US) : “ALICE first collision data demonstrates success of Wright Lab detector upgrade” 

    1

    From Wright Laboratory

    At

    Yale University (US)

    November 12, 2021 {Just today in social media.]

    Wright Lab’s Relativistic Heavy Ion Group (RHIG), led by professor of physics Helen Caines and D. Allan Bromley Professor Emeritus of Physics John Harris, has been taking advantage of the extended 3-year shutdown of the Large Hadron Collider (LHC)–the world’s largest and most powerful particle accelerator located at the Center for European Nuclear Research (CERN) in Geneva, Switzerland–to contribute to the upgrade of one of the LHC’s detectors, called A Large Ion Collider Experiment (ALICE).

    1
    Image courtesy of Yale RHIG/ALICE Collaboration.

    Iconic view of the European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN] ALICE Detector.

    European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN].

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

    CERN LHC tunnel and tube.

    SixTRack CERN LHC particles.

    ALICE uses collisions of heavy nuclei, as well as proton-proton and proton-nucleus collisions, to study the physics of strongly interacting matter at the highest energy densities reached so far in the laboratory. The primary goal of the experiment is to re-create the quark-gluon plasma (QGP) state of matter, which is predicted by the Standard Model of particle physics to have existed ten millionths of a second after the Big Bang.

    After several years of construction and then installation during the LHC shutdown, the upgraded LHC started delivering stable beams in collision for detectors on October 27, 2021. ALICE immediately started taking data to test its new detector systems—including a completely new silicon inner tracking system (10 m2 of active silicon area and nearly 13 billion pixels) and new Time Projection Chamber (TPC) endcap readout–as well as its online and offline software.

    Wright Lab research scientist Nikolai Smirnov and the late Richard Majka, also a research scientist in Wright Lab’s RHIG, were in charge of the assembly and testing of ALICE’s inner Gas Electron Multiplier (GEM) TPC chambers in Wright Lab. Majka also served as the U.S. Project Leader for the U.S. Department of Energy (DOE) supported GEM-TPC construction project effort. Graduate students from RHIG also played an important role in the R&D for this new type of TPC readout prior to its construction.

    The GEM-TPC (cylindrical tracking detector 5 meters in diameter, 5 meters long) and its new readout electronics feature a continuous readout mode that allows ALICE to record the thousands of tracks produced in Pb-Pb collisions at event rates of 50 kHz leading to a staggering data rate of 3.5 TB/s.

    Seen in the online display (see snapshot pictured, above) is the real-time sequence of the continuous TPC data stream in 11 millisecond slices. Tracks from individual proton-proton collision events can be seen as they curve through the magnetic field along the cylindrical axis. Given the continuously streaming, real-time data readout and the new detector systems, ALICE expects to accumulate 50 times more heavy-ion collision data in the upcoming LHC Run 3 than in Runs 1 and 2 combined.

    In addition to leading construction of the inner sectors of the ALICE TPC upgrade, RHIG at Yale has been engaged with the ALICE Collaboration since its beginning. The Wright Lab group has contributed significantly to ALICE analyses and papers, as well as the original design of the detector. The Wright Lab group assembled, tested, calibrated, and installed the electromagnetic calorimeter (EMCal) in ALICE. Harris is a past chair of the ALICE Collaboration Board. Furthermore, the group engages in simulations, R&D, design and prototyping of future detectors.

    See the full article here .

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    Wright Lab is advancing the frontiers of fundamental physics through a broad research program in nuclear, particle, and astrophysics that includes precision studies of neutrinos; searches for dark matter; investigations of the building blocks and interactions of matter; exploration of quantum science and its applications for fundamental physics experiments; and observations of the early Universe. The laboratory’s unique combination of on-site state-of-the-art research facilities, technical infrastructure, and interaction spaces supports innovative instrumentation development, hands-on research, and training the next generation of scientists. Wright Lab is a part of the Yale Department of Physics and houses several Yale University core facilities that serve researchers across Yale’s Science Hill and beyond.

    Mission

    The mission of Yale Wright Laboratory is to advance understanding of the physical world, from the smallest particles to the evolution of the Universe, by engaging in fundamental research, developing novel applications, training future leaders in research and development, educating scholars, and enabling discovery.

    Wright Lab supports a diverse community of scientists, staff, and students who advance our mission and fosters cross-disciplinary collaborations across Yale University and worldwide.

    Climate Statement

    The Yale Wright Laboratory is committed to diversity, equity, and inclusion among all students, staff, and faculty. The goal of our lab community is to provide a safe and supportive environment for research, teaching, and mentoring. Diversity, equity, and inclusion are core principles of our work place and part of the excellence we aim for.

    Resources

    Wright Lab, the Yale Department of Physics, and Yale University offer a number of resources on topics of climate, diversity, equity, and inclusion. In addition, the Committee on Climate and Diversity in the Physics Department is a point of contact for all questions and concerns. Please visit the following links for more information and a list of resources.

    Collaboration

    With its on-site core facilities and research program, Wright Lab fosters cross-disciplinary research collaborations across Yale University and worldwide. Wright Lab works with the Yale Center for Research Computing (YCRC) on novel solutions to the research computing challenges in nuclear, particle and astrophysics, and collaborates with the Yale Center for Astronomy and Astrophysics (YCAA) on understanding dark matter in the Universe. Quantum sensors and techniques jointly developed with the Yale Quantum Institute (YQI) are used for axion searches at Wright Lab.

    Wright Lab also has strong, interdisciplinary partnerships with the Yale Center for Collaborative Arts and Media, the Yale Peabody Museum of Natural History, and Yale Pathways to Science.

    Funding

    Wright Laboratory gratefully acknowledges support from the Alfred P. Sloan Foundation; the Department of Energy, Office of Science, High Energy Physics and Nuclear Physics; the Heising-Simons Foundation; the Krell Institute; the National Science Foundation; and Yale University.

    Yale University (US) is a private Ivy League research university in New Haven, Connecticut. Founded in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and one of the nine Colonial Colleges chartered before the American Revolution. The Collegiate School was renamed Yale College in 1718 to honor the school’s largest private benefactor for the first century of its existence, Elihu Yale. Yale University is consistently ranked as one of the top universities and is considered one of the most prestigious in the nation.

    Chartered by Connecticut Colony, the Collegiate School was established in 1701 by clergy to educate Congregational ministers before moving to New Haven in 1716. Originally restricted to theology and sacred languages, the curriculum began to incorporate humanities and sciences by the time of the American Revolution. In the 19th century, the college expanded into graduate and professional instruction, awarding the first PhD in the United States in 1861 and organizing as a university in 1887. Yale’s faculty and student populations grew after 1890 with rapid expansion of the physical campus and scientific research.

    Yale is organized into fourteen constituent schools: the original undergraduate college, the Yale Graduate School of Arts and Sciences and twelve professional schools. While the university is governed by the Yale Corporation, each school’s faculty oversees its curriculum and degree programs. In addition to a central campus in downtown New Haven, the university owns athletic facilities in western New Haven, a campus in West Haven, Connecticut, and forests and nature preserves throughout New England. As of June 2020, the university’s endowment was valued at $31.1 billion, the second largest of any educational institution. The Yale University Library, serving all constituent schools, holds more than 15 million volumes and is the third-largest academic library in the United States. Students compete in intercollegiate sports as the Yale Bulldogs in the NCAA Division I – Ivy League.

    As of October 2020, 65 Nobel laureates, five Fields Medalists, four Abel Prize laureates, and three Turing award winners have been affiliated with Yale University. In addition, Yale has graduated many notable alumni, including five U.S. Presidents, 19 U.S. Supreme Court Justices, 31 living billionaires, and many heads of state. Hundreds of members of Congress and many U.S. diplomats, 78 MacArthur Fellows, 252 Rhodes Scholars, 123 Marshall Scholars, and nine Mitchell Scholars have been affiliated with the university.

    Research

    Yale is a member of the Association of American Universities (AAU) (US) and is classified among “R1: Doctoral Universities – Very high research activity”. According to the National Science Foundation (US), Yale spent $990 million on research and development in 2018, ranking it 15th in the nation.

    Yale’s faculty include 61 members of the National Academy of Sciences (US), 7 members of the National Academy of Engineering (US) and 49 members of the American Academy of Arts and Sciences (US). The college is, after normalization for institution size, the tenth-largest baccalaureate source of doctoral degree recipients in the United States, and the largest such source within the Ivy League.

    Yale’s English and Comparative Literature departments were part of the New Criticism movement. Of the New Critics, Robert Penn Warren, W.K. Wimsatt, and Cleanth Brooks were all Yale faculty. Later, the Yale Comparative literature department became a center of American deconstruction. Jacques Derrida, the father of deconstruction, taught at the Department of Comparative Literature from the late seventies to mid-1980s. Several other Yale faculty members were also associated with deconstruction, forming the so-called “Yale School”. These included Paul de Man who taught in the Departments of Comparative Literature and French, J. Hillis Miller, Geoffrey Hartman (both taught in the Departments of English and Comparative Literature), and Harold Bloom (English), whose theoretical position was always somewhat specific, and who ultimately took a very different path from the rest of this group. Yale’s history department has also originated important intellectual trends. Historians C. Vann Woodward and David Brion Davis are credited with beginning in the 1960s and 1970s an important stream of southern historians; likewise, David Montgomery, a labor historian, advised many of the current generation of labor historians in the country. Yale’s Music School and Department fostered the growth of Music Theory in the latter half of the 20th century. The Journal of Music Theory was founded there in 1957; Allen Forte and David Lewin were influential teachers and scholars.

    In addition to eminent faculty members, Yale research relies heavily on the presence of roughly 1200 Postdocs from various national and international origin working in the multiple laboratories in the sciences, social sciences, humanities, and professional schools of the university. The university progressively recognized this working force with the recent creation of the Office for Postdoctoral Affairs and the Yale Postdoctoral Association.

    Notable alumni

    Over its history, Yale has produced many distinguished alumni in a variety of fields, ranging from the public to private sector. According to 2020 data, around 71% of undergraduates join the workforce, while the next largest majority of 16.6% go on to attend graduate or professional schools. Yale graduates have been recipients of 252 Rhodes Scholarships, 123 Marshall Scholarships, 67 Truman Scholarships, 21 Churchill Scholarships, and 9 Mitchell Scholarships. The university is also the second largest producer of Fulbright Scholars, with a total of 1,199 in its history and has produced 89 MacArthur Fellows. The U.S. Department of State Bureau of Educational and Cultural Affairs ranked Yale fifth among research institutions producing the most 2020–2021 Fulbright Scholars. Additionally, 31 living billionaires are Yale alumni.

    At Yale, one of the most popular undergraduate majors among Juniors and Seniors is political science, with many students going on to serve careers in government and politics. Former presidents who attended Yale for undergrad include William Howard Taft, George H. W. Bush, and George W. Bush while former presidents Gerald Ford and Bill Clinton attended Yale Law School. Former vice-president and influential antebellum era politician John C. Calhoun also graduated from Yale. Former world leaders include Italian prime minister Mario Monti, Turkish prime minister Tansu Çiller, Mexican president Ernesto Zedillo, German president Karl Carstens, Philippine president José Paciano Laurel, Latvian president Valdis Zatlers, Taiwanese premier Jiang Yi-huah, and Malawian president Peter Mutharika, among others. Prominent royals who graduated are Crown Princess Victoria of Sweden, and Olympia Bonaparte, Princess Napoléon.

    Yale alumni have had considerable presence in U.S. government in all three branches. On the U.S. Supreme Court, 19 justices have been Yale alumni, including current Associate Justices Sonia Sotomayor, Samuel Alito, Clarence Thomas, and Brett Kavanaugh. Numerous Yale alumni have been U.S. Senators, including current Senators Michael Bennet, Richard Blumenthal, Cory Booker, Sherrod Brown, Chris Coons, Amy Klobuchar, Ben Sasse, and Sheldon Whitehouse. Current and former cabinet members include Secretaries of State John Kerry, Hillary Clinton, Cyrus Vance, and Dean Acheson; U.S. Secretaries of the Treasury Oliver Wolcott, Robert Rubin, Nicholas F. Brady, Steven Mnuchin, and Janet Yellen; U.S. Attorneys General Nicholas Katzenbach, John Ashcroft, and Edward H. Levi; and many others. Peace Corps founder and American diplomat Sargent Shriver and public official and urban planner Robert Moses are Yale alumni.

    Yale has produced numerous award-winning authors and influential writers, like Nobel Prize in Literature laureate Sinclair Lewis and Pulitzer Prize winners Stephen Vincent Benét, Thornton Wilder, Doug Wright, and David McCullough. Academy Award winning actors, actresses, and directors include Jodie Foster, Paul Newman, Meryl Streep, Elia Kazan, George Roy Hill, Lupita Nyong’o, Oliver Stone, and Frances McDormand. Alumni from Yale have also made notable contributions to both music and the arts. Leading American composer from the 20th century Charles Ives, Broadway composer Cole Porter, Grammy award winner David Lang, and award-winning jazz pianist and composer Vijay Iyer all hail from Yale. Hugo Boss Prize winner Matthew Barney, famed American sculptor Richard Serra, President Barack Obama presidential portrait painter Kehinde Wiley, MacArthur Fellow and contemporary artist Sarah Sze, Pulitzer Prize winning cartoonist Garry Trudeau, and National Medal of Arts photorealist painter Chuck Close all graduated from Yale. Additional alumni include architect and Presidential Medal of Freedom winner Maya Lin, Pritzker Prize winner Norman Foster, and Gateway Arch designer Eero Saarinen. Journalists and pundits include Dick Cavett, Chris Cuomo, Anderson Cooper, William F. Buckley, Jr., and Fareed Zakaria.

    In business, Yale has had numerous alumni and former students go on to become founders of influential business, like William Boeing (Boeing, United Airlines), Briton Hadden and Henry Luce (Time Magazine), Stephen A. Schwarzman (Blackstone Group), Frederick W. Smith (FedEx), Juan Trippe (Pan Am), Harold Stanley (Morgan Stanley), Bing Gordon (Electronic Arts), and Ben Silbermann (Pinterest). Other business people from Yale include former chairman and CEO of Sears Holdings Edward Lampert, former Time Warner president Jeffrey Bewkes, former PepsiCo chairperson and CEO Indra Nooyi, sports agent Donald Dell, and investor/philanthropist Sir John Templeton,

    Yale alumni distinguished in academia include literary critic and historian Henry Louis Gates, economists Irving Fischer, Mahbub ul Haq, and Nobel Prize laureate Paul Krugman; Nobel Prize in Physics laureates Ernest Lawrence and Murray Gell-Mann; Fields Medalist John G. Thompson; Human Genome Project leader and National Institutes of Health (US) director Francis S. Collins; brain surgery pioneer Harvey Cushing; pioneering computer scientist Grace Hopper; influential mathematician and chemist Josiah Willard Gibbs; National Women’s Hall of Fame inductee and biochemist Florence B. Seibert; Turing Award recipient Ron Rivest; inventors Samuel F.B. Morse and Eli Whitney; Nobel Prize in Chemistry laureate John B. Goodenough; lexicographer Noah Webster; and theologians Jonathan Edwards and Reinhold Niebuhr.

    In the sporting arena, Yale alumni include baseball players Ron Darling and Craig Breslow and baseball executives Theo Epstein and George Weiss; football players Calvin Hill, Gary Fenick, Amos Alonzo Stagg, and “the Father of American Football” Walter Camp; ice hockey players Chris Higgins and Olympian Helen Resor; Olympic figure skaters Sarah Hughes and Nathan Chen; nine-time U.S. Squash men’s champion Julian Illingworth; Olympic swimmer Don Schollander; Olympic rowers Josh West and Rusty Wailes; Olympic sailor Stuart McNay; Olympic runner Frank Shorter; and others.

     
  • richardmitnick 2:02 pm on November 17, 2021 Permalink | Reply
    Tags: "ALICE takes the next step in understanding the interaction among hadrons", , ALICE at CERN (CH), , , , , , , , , Studying the residual interaction between two-quark and three-quark particles., The ɸ meson is regarded as a possible vehicle of the interaction among baryons (hadrons consisting of three quarks) that contain one or more strange quarks-called hyperons (Y).   

    From ALICE at CERN (CH) : “ALICE takes the next step in understanding the interaction among hadrons” 

    European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN]

    From ALICE at CERN (CH)

    17 November, 2021

    1
    An artistic representation of the interaction between a proton (with two up and a down quark) and a ɸ meson (with strange-antistrange quarks) as they emerge with an interdistance of the order of a femtometre from a proton-proton collision at the LHC. Image: ALICE collaboration.

    In a recently published article in Physical Review Letters, the ALICE collaboration has used a method called femtoscopy to study the residual interaction between two-quark and three-quark particles. Through this measurement, an interaction between the ɸ meson (strange-antistrange quarks) and a proton (two up and one down quarks) was unveiled for the first time.

    Since the ɸ meson is not electrically charged, an interaction between the proton and the ɸ cannot be of electromagnetic origin and can only be attributed to the residual strong interaction. The strong interaction is what holds together quarks inside hadrons (like the proton and the ɸ meson), while the residual strong interaction is the force that acts between hadrons. This is the interaction that holds protons and neutrons together in the form of atomic nuclei.

    But unlike the residual strong interaction between protons and neutrons, that can be studied in stable bound states like the nuclei, the interaction between unstable hadrons produced in particle collisions is very difficult to observe. It was found to be possible in the LHC using an approach called femtoscopy. Hadrons in the LHC collisions are produced very close to each other, at distances of about 10-15 m (femtometre, hence the name femtoscopy). This scale matches the range of the residual strong force, giving them a brief chance to interact before flying away. As a result, pairs of hadrons that experience an attractive interaction will move slightly closer to each other, while for a repulsive interaction, the contrary occurs. Both effects can be clearly observed through detailed analysis of the measured relative velocities of the particles.

    The knowledge of the p-ɸ (proton-ɸ meson) interaction is of twofold interest in nuclear physics. First, this interaction is an anchor point for searches of the partial restoration of chiral symmetry. The left- and right-handed (chiral) symmetry that characterizes the strong interaction is found to be broken in Nature and this effect is responsible for the much larger mass of hadrons, like the proton and neutron, with respect to the masses of the quarks that constitute them. Hence, chiral symmetry is connected to the origin of mass itself! A possible way to search for restoration of chiral symmetry and shed light on the mechanism that generates mass is by studying modifications of the properties of ɸ mesons within dense nuclear matter formed in collisions at the LHC. However, for this purpose, it is essential that the simple two body p-ɸ interaction in vacuum is understood first.

    The second point of interest is that, due to its strange-antistrange quark content, the ɸ meson is regarded as a possible vehicle of the interaction among baryons (hadrons consisting of three quarks) that contain one or more strange quarks, called hyperons (Y). Depending on the strength of this interaction, hyperons may form the core of neutron stars, among the densest and least understood astrophysical objects. Direct measurement of the Y-ɸ interaction strength although feasible has not yet been carried out, but already today this quantity can be related to the p-ɸ findings via fundamental symmetries. Therefore, measuring p-ɸ interaction provides indirect access to the Y-Y interaction in neutron stars.

    The moderate interaction strength measured by ALICE provides a quantitative reference for further studies of the ɸ properties within the nuclear medium and also translates into a negligible interaction among hyperons in neutron stars. More accurate measurements will follow during the upcoming LHC Run 3 and Run 4 allowing to significantly improve the precision of the extracted parameters and also to pin down the Y-ɸ interaction directly.

    See the full article here .


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  • richardmitnick 11:46 am on July 7, 2021 Permalink | Reply
    Tags: "ALICE is “FIT” for Run 3 after last new subdetector installation", , ALICE at CERN (CH), , , , ,   

    From ALICE at CERN (CH) : “ALICE is “FIT” for Run 3 after last new subdetector installation” 

    From ALICE at CERN (CH)

    6 July, 2021

    1
    The FIT detector (Fast Interaction Trigger) was installed in the ALICE cavern during LS2 in June 2021 (Image: CERN)

    The ALICE detector is being steadily reassembled after three years of dismantling, building, testing and reinstallation of the subdetectors. This major LHC experiment received its last new subdetector on Monday, 21 June 2021, when the Fast Interaction Trigger (FIT) was lowered into the Point 2 cavern. The 300-kg disk, together with the three other FIT arrays, will serve as an interaction trigger, online luminometer, initial indicator of the vertex position and forward multiplicity counter. It is now secured next to the central tracking detectors inside the L3 magnet.

    This polyvalent subdetector was conceptualised, reviewed and approved by the ALICE Technical Board in early 2013. It is the fruit of an intense R&D effort involving prototype tests at the Proton Synchrotron. Among the 60-plus scientists from 17 institutions who contributed to the FIT design, construction, testing and installation, the Muscovite team at the Russian Institute for Nuclear Research faced major challenges with the design of the new, fully digital, front-end electronics and readout system.

    FIT relies on three state-of-the-art detector technologies underpinning components grouped into five arrays surrounding the LHC beamline, at -1, +3, +17, and -19 metres from the interaction point. The diversity of the detection techniques and the scattered positions are needed in order to fulfil the subdetector’s many required functionalities. Among the three components that make up the FIT detector, the FT0 is the fastest: comprising 208 optically separated quartz radiators, its expected time resolution for high-multiplicity heavy-ion collisions is about 7 picoseconds, ranking FIT among the fastest detectors in high-energy physics experiments. This impressively precise timing is crucial for online vertex determination and for identifying charged lepton and hadron species using time-of-flight.

    The second component, a segmented scintillator called FV0, innovates with a novel light-collection scheme designed and manufactured at UNAM, Mexico. The largest of the three components, the FV0 makes use of its size to provide optimal acceptance, which is vital for extracting centrality and determining the event plane – key parameters characterising a heavy-ion collision.

    Finally, the Forward Diffractive Detector (FDD), consisting of two nearly identical scintillator arrays, can tag photon-induced or diffractive processes by recognising the absence of activity in the forward direction. It also serves as a background monitoring tool.

    Now that it is soundly wedged inside the ALICE detector, the FIT is expected to stay there until the end of Run 4. Its installation, which comes after that of the Time Projection Chamber, the Muon Forward Tracker and the Inner Tracking System, brings ALICE one step closer to the end of LS2 activities. The closing of the L3 magnet door and the installation of the final station of the muon spectrometer are scheduled to take place by the end of July and the end of August, respectively. Then a few months of commissioning will take ALICE to the start of Run 3, scheduled for the end of February 2022.

    See the full article here .


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  • richardmitnick 4:11 pm on June 10, 2021 Permalink | Reply
    Tags: "ALICE finds that charm hadronisation differs at the LHC", , ALICE at CERN (CH), , , , ,   

    From ALICE at CERN (CH) : “ALICE finds that charm hadronisation differs at the LHC” 

    From ALICE at CERN (CH)

    10 June, 2021
    Andrea Dainese

    New measurements by the ALICE collaboration show that the way charm quarks form hadrons in proton-proton collisions differs significantly from expectations based on electron collider measurements.

    Quarks are among the elementary particles of the Standard Model of Particle Physics.

    Besides up and down quarks, which are the basic building blocks of ordinary matter in the Universe, four other quark flavours exist and are also abundantly produced in collisions at particle accelerators like the CERN Large Hadron Collider. Quarks are not observed in isolation due to a fundamental aspect of the strong interaction, known as colour charge confinement. Confinement requires particles that carry the charge of the strong interaction, called colour, to form states that are colour-neutral. This in turn forces quarks to undergo a process of hadronisation, i.e. to form hadrons, which are composite particles mostly made of a quark and an antiquark (mesons) or of three quarks (baryons). The only exception is the heaviest quark, the top, which decays before it has time to hadronise.

    At particle accelerators, quarks with a large mass, such as the charm quark, are produced only in the initial interactions between the colliding particles. Depending on the type of beam used, these can be electron-positron, electron-proton or proton-proton collisions (as at the LHC). The subsequent hadronisation of charm quarks into mesons (D0, D+, Ds) or baryons (𝛬c, 𝛯c, …) occurs on a long space-time scale and was considered to be universal – that is, independent of the species of the colliding particles – until the recent findings by the ALICE collaboration.

    The large data samples collected during Run 2 of the LHC allowed ALICE to count the vast majority of charm quarks produced in the proton-proton collisions by reconstructing the decays of all charm meson species and of the most abundant charm baryons (𝛬c and 𝛯c). The charm quarks were found to form baryons almost 40% of the time, which is four times more often than what was expected based on measurements previously made at colliders with electron beams (e+e- and ep in the figure below).

    These measurements show that the process of colour-charge confinement and hadron formation is still a poorly understood aspect of the strong interaction. Current theoretical explanations of baryon enhancement include the combination of multiple quarks produced in proton-proton collisions and new mechanisms in the neutralisation of the colour charge. Additional measurements during the next run of the LHC will allow these theories to be scrutinised and further our knowledge of the strong interaction.

    See the full article here .


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  • richardmitnick 11:40 am on December 9, 2020 Permalink | Reply
    Tags: "ALICE opens avenue for high-precision studies of strong force", , ALICE at CERN (CH), , , One of the biggest challenges in nuclear physics today is understanding the strong interaction between hadrons with different quark content from first principles., , , , The collaboration shows how proton-proton collisions at the Large Hadron Collider can reveal the strong interaction between composite particles called hadrons.   

    From ALICE at CERN (CH): “ALICE opens avenue for high-precision studies of strong force” 

    From From ALICE at CERN (CH)

    December 10, 2020

    1
    An artist’s impression of the ALICE study of the interaction between the rarest of the hyperons, Omega (Ω) hyperon (left), which contains three strange quarks, and a proton (right).

    The collaboration shows how proton-proton collisions at the Large Hadron Collider can reveal the strong interaction between composite particles called hadrons.

    In a paper published today in Nature, the ALICE collaboration describes a technique that opens a door to high-precision studies at the Large Hadron Collider (LHC) of the dynamics of the strong force between hadrons.

    Hadrons are composite particles made of two or three quarks bound together by the strong interaction, which is mediated by gluons. This interaction also acts between hadrons, binding nucleons (protons and neutrons) together inside atomic nuclei. One of the biggest challenges in nuclear physics today is understanding the strong interaction between hadrons with different quark content from first principles, that is, starting from the strong interaction between the hadrons’ constituent quarks and gluons.

    Calculations known as lattice quantum chromodynamics (QCD) can be used to determine the interaction from first principles, but these calculations provide reliable predictions only for hadrons containing heavy quarks, such as hyperons, which have one or more strange quarks. In the past, these interactions were studied by colliding hadrons together in scattering experiments, but these experiments are difficult to perform with unstable (i.e. rapidly decaying) hadrons such as hyperons. This difficulty has so far prevented a meaningful comparison between measurements and theory for hadron-hadron interactions involving hyperons.

    Enter the new study from the collaboration behind ALICE, one of the main experiments at the LHC. The study shows how a technique based on measuring the momentum difference between hadrons produced in proton-proton collisions at the LHC can be used to reveal the dynamics of the strong interaction between hyperons and nucleons, potentially for any pair of hadrons. The technique is called femtoscopy because it allows the investigation of spatial scales close to 1 femtometre (10−15 metres) – about the size of a hadron and the spatial range of the strong-force action.

    This method has previously allowed the ALICE team to study interactions involving the Lambda (Λ) and Sigma (Σ) hyperons, which contain one strange quark plus two light quarks, as well as the Xi (Ξ) hyperon, which is composed of two strange quarks plus one light quark. In the new study, the team used the technique to uncover with high precision the interaction between a proton and the rarest of the hyperons, the Omega (Ω) hyperon, which contains three strange quarks.

    “The precise determination of the strong interaction for all types of hyperons was unexpected,” says ALICE physicist Laura Fabbietti, professor at the Technical University of Munich. “This can be explained by three factors: the fact that the LHC can produce hadrons with strange quarks in abundance, the ability of the femtoscopy technique to probe the short-range nature of the strong interaction, and the excellent capabilities of the ALICE detector to identify particles and measure their momenta.”

    “Our new measurement allows for a comparison with predictions from lattice QCD calculations and provides a solid testbed for further theoretical work,” says ALICE spokesperson Luciano Musa. “Data from the next LHC runs should give us access to any hadron pair.”

    “ALICE has opened a new avenue for nuclear physics at the LHC – one that involves all types of quarks,” concludes Musa.

    /Public Release. The material in this public release comes from the originating organization and may be of a point-in-time nature, edited for clarity, style and length. View in full here.

    See the full article here .


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