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  • richardmitnick 10:22 am on March 25, 2019 Permalink | Reply
    Tags: , , For Phase 3 installation of the full decay VerteX Detector (VXD) was completed. With this change Belle II is now fully equipped and ready to take physics data., KEK Belle II SuperKEKB accelerator, KEK Inter-University Research Institute Corporation, , ,   

    From KEK Inter-University Research Institute Corporation: “SuperKEKB Phase 3 (Belle II Physics Run) Starts” 

    From KEK Inter-University Research Institute Corporation

    2019/03/11

    On March 11th, 2019, Phase 3 operation of the SuperKEKB project began successfully, marking a major milestone in the development of Japan’s leading particle collider. This phase will be the physics run of the project, in which the Belle II experiment will start taking data with a fully instrumented detector.

    The KEKB accelerator, operated from 1999 to 2010, currently holds the world record luminosity for an electron-positron collider. SuperKEKB, its successor, plans to reach a luminosity 40 times greater over its lifetime.

    Belle II and SuperKEKB are poised to become the world’s first Super B factory facility. Belle II aims to accumulate 50 times more data than its predecessor, Belle, and to seek out new physics hidden in subatomic particles that could shed light on mysteries of the early universe.

    Belle II KEK High Energy Accelerator Research Organization Tsukuba, Japan

    The Belle experiment, which completed data taking in 2010, along with its competitor in the United States BaBar, demonstrated Charge-Parity Violation (CPV) in weak interactions of B mesons.

    SLAC BaBar


    SLAC BaBar

    This discovery was explicitly recognized by the Nobel Foundation and resulted in the 2008 Nobel Prize for Physics being awarded to Professors Makoto Kobayashi and Toshihide Maskawa for their work developing the theory of CPV in weak interactions.

    A major upgrade, the Belle II/SuperKEKB facility, began construction at the end of 2010. SuperKEKB will achieve its goal of 40 times KEKB’s luminosity by shrinking the beams to “nano-beam” size, at the collision point, 20 times smaller than the beam sizes achieved at KEKB while simultaneously doubling the beam currents. These changes will result in much larger quantities of data as well as greater beam backgrounds. Belle II was designed to handle these conditions.

    In February 2016, Phase 1 commissioning of the SuperKEKB accelerator was successfully completed. Low-emittance Ampère-level beams were circulated in both rings, but no collisions were possible. This was followed by the installation of the superconducting final focus magnets and the Belle II outer detector. Phase 2, the pilot run of Belle II, began in March of 2018, with the first collisions recorded in the early hours of April 26th. Initial results from Phase 2 were shown at international conferences in 2018.

    For Phase 3, installation of the full decay VerteX Detector (VXD) was completed. With this change, Belle II is now fully equipped and ready to take physics data.

    See the full article here .

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    KEK-Accelerator Laboratory

    KEK, the High Energy Accelerator Research Organization, is one of the world’s leading accelerator science research laboratories, using high-energy particle beams and synchrotron light sources to probe the fundamental properties of matter. With state-of-the-art infrastructure, KEK is advancing our understanding of the universe that surrounds us, its mechanisms and their control. Our mission is:

    • To make discoveries that address the most compelling questions in a wide range of fields, including particle physics, nuclear physics, materials science, and life science. We at KEK strive to make the most effective use of the funds entrusted by Japanese citizens for the benefit of all, by adding to knowledge and improving the technology that protects the environment and serves the economy, academia, and public health; and

    • To act as an Inter-University Research Institute Corporation, a center of excellence that promotes academic research by fulfilling the needs of researchers in universities across the country and by cooperating extensively with researchers abroad; and

    • To promote national and international collaborative research activities by providing advanced research facilities and opportunities. KEK is committed to be in the forefront of accelerator science in Asia-Oceania, and to cooperate closely with other institutions, especially with Asian laboratories.

    Established in 1997 in a reorganization of the Institute of Nuclear Study, University of Tokyo (established in 1955), the National Laboratory for High Energy Physics (established in 1971), and the Meson Science Laboratory of the University of Tokyo (established in 1988), KEK serves as a center of excellence for domestic and foreign researchers, providing a wide variety of research opportunities. In addition to the activities at the Tsukuba Campus, KEK is now jointly operating a high-intensity proton accelerator facility (J-PARC) in Tokai village, together with the Japan Atomic Energy Agency (JAEA). Over 600 scientists, engineers, students and staff perform research activities on the Tsukuba and Tokai campuses. KEK attracts nearly 100,000 national and international researchers every year (total man-days), and provides excellent research facilities and opportunities to many students and post-doctoral fellows each year.

     
  • richardmitnick 3:28 pm on September 20, 2018 Permalink | Reply
    Tags: , , KEK Belle II SuperKEKB accelerator, , , ,   

    From Science News: “Three new physics experiments could revamp the standard model” 

    From Science News

    September 19, 2018
    Emily Conover

    Physicists build giant machines to study tiny particles.

    1
    MASSIVE MACHINES A researcher stands in the cavernous spectrometer of KATRIN, an experiment in Germany to measure the mass of particles called neutrinos. Michael Zacher

    Diana Parno’s head swam when she first stepped inside the enormous, metallic vessel of the experiment KATRIN. Within the house-sized, oblong structure, everything was symmetrical, clean and blindingly shiny, says Parno, a physicist at Carnegie Mellon University in Pittsburgh. “It was incredibly disorienting.”

    Now, electrons — thankfully immune to bouts of dizziness — traverse the inside of this zeppelin-shaped monstrosity located in Karlsruhe, Germany. Building the experiment took years and tens of millions of dollars. Why create such an extreme apparatus? It’s all part of a bid to measure the mass of itty-bitty subatomic particles known as neutrinos.

    KATRIN, which is short for Karlsruhe Tritium Neutrino Experiment, started test runs in May. The experiment is part of a multipronged approach to the study of particle physics, one of dozens of detectors built in an assortment of odd-looking shapes and sizes. Their mission: dive deep into the standard model, particle physicists’ theory of the subatomic building blocks of matter — and maybe overthrow it.

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


    Standard Model of Particle Physics from Symmetry Magazine

    Developed in the 1960s and ’70s, the standard model has some sizable holes: It can’t explain dark matter — an ethereal substance so far detected only by its gravitational effects — or dark energy, a mysterious oomph that causes the cosmos to expand at an increasing rate. The theory also can’t explain why the universe is made mostly of matter, while antimatter is rare (SN: 9/2/17, p. 15). So physicists are on a quest to revamp particle physics by probing the standard model’s weak points.

    Major facilities like the Large Hadron Collider — the gargantuan accelerator located at CERN near Geneva — haven’t yet found where the standard model goes wrong (SN: 10/1/16, p. 12).

    LHC

    CERN map


    CERN LHC Tunnel

    CERN LHC particles

    Instead, particle physics experiments have confirmed standard model predictions again and again. “In some sense we are victims of our own success,” says Juan Rojo, a theoretical physicist at Vrije Universiteit Amsterdam. “We don’t have hints about what is the next step.”

    New experiments like KATRIN might be able to ferret out answers. Also joining the ranks are Muon g-2 (pronounced “gee minus two”) at Fermilab in Batavia, Ill., and Belle II in Tsukuba, Japan.

    FNAL Muon g-2 studio

    SuperKEKB accelerator Belle II Credit KEK

    A behind-the-scenes look at these experiments reveals the sweat, joy and sacrifice that goes into each of these difficult enterprises. These efforts involve hundreds of researchers, sport price tags in the tens of millions of dollars and require major technological undertakings: intricate electronics, powerful magnets and ultraclean conditions. Researchers have built complex apparatuses with their own hands, lugged tons of equipment across continents and cleaned the insides of detectors until they gleam.

    Here’s a glimpse at three of the latest standard model challengers.

    Belle II

    KEK High Energy Accelerator Research Organization
    Tsukuba, Japan
    Approximate cost: $50 million

    Belle II KEK High Energy Accelerator Research Organization Tsukuba, Japan

    How it works

    Electrons and their antimatter partners, positrons, take laps around a 3-kilometer long, ring-shaped accelerator and collide at the center of the Belle II detector, producing a class of particles called B mesons. These particles contain a bottom quark, an exotic particle not found in run-of-the-mill matter. Scientists sift through the data produced when B mesons decay inside the 8-meter-tall detector to learn about the particles’ weird ways.

    ____________________________________________
    3
    T. Tibbitts, High Energy Accelerator Research Organization, Institute of Particle and Nuclear Studies

    1. An accelerator sends electrons from one end and positrons from the other into Belle II.

    2. Tracking detectors follow particles’ paths after collision, pinpointing B mesons.

    3. Quartz sensors distinguish between similar types of particles.

    4. A calorimeter measures energies of particles.

    5. Outer layers spot particles that get past inner sections.

    ____________________________________________

    OK, but why?

    Certain B mesons seem to prefer to decay into electrons, rather than their heavier cousins, muons (SN: 5/13/17, p. 16). That goes against the standard model, which says electrons and muons should appear in equal amounts. If this unexpected behavior holds up to scrutiny, something big must be wrong with the theory. B mesons also partake in a process called CP violation, in which antimatter and matter don’t behave like perfect mirror images.

    Studying CP violation might help scientists understand why the universe is composed of matter and not antimatter. In the Big Bang, matter and antimatter were produced in equal measure and should have annihilated into nothingness, but somehow matter gained an upper hand. It’s “the most fundamental question human beings can ask … ‘Why are we here?’ ” says physics graduate student Robert Seddon.

    3
    NARROW FOCUS Scientists insert superconducting magnets into the center of Belle II. The magnets focus the beams of electrons and positrons that collide inside the detector. KEK IPNS

    KATRIN

    Karlsruhe Institute of Technology, Germany
    Approximate cost: $70 million

    KATRIN experiment aims to measure the mass of the neutrino using a huge device called a spectrometer (interior shown)Karlsruhe Institute of Technology, Germany

    How it works

    Physicists aim to measure the mass of neutrinos, wily subatomic particles that are nearly impossible to detect. At one end of the 70-meter-long KATRIN, radioactive decays of tritium produce electrons and the antimatter twins of neutrinos. Those antineutrinos escape while the electrons cruise through KATRIN’s blimp-shaped tank and are detected at the other end (SN Online: 10/18/16). The tank, a spectrometer, divvies up the particles according to their energies. Some energy from each tritium decay goes to generating the antineutrino’s mass. That limits how much energy the electron gets. So measuring the electrons’ energies can reveal the mass of neutrinos. KATRIN should officially start taking data next spring.

    ____________________________________________
    4
    KATRIN

    5
    T. Tibbitts, M. Arenz et al/J. of Instrumentation 2016

    1. Tritium decays, releasing electrons and antineutrinos, which escape.

    2. Electrons travel along beamline to spectrometer.

    3. The spectrometer sorts electrons by their energies

    4. A magnetic field (dotted lines) shepherds high-energy electrons to a detector at the other end.

    5. An electric field turns low-energy electrons back.

    6. Magnets focus electrons onto the detector.

    ____________________________________________

    OK, but why?

    A neutrino’s mass is a tiny fraction of an electron’s. “Why is it so light?” Parno asks. “That’s mysterious.” The standard model initially predicted that neutrinos have no mass at all. But measurements indicate that the particles must have mass, though how much is still a question. Neutrinos barely interact with matter and are incredibly numerous: Billions of neutrinos sail through your thumbnail each second. These particles are so quirky that scientists want to know more.
    Radioactive rules

    It all starts with tritium. This radioactive version of hydrogen, pumped through the experiment in a gaseous form, emits 100 billion antineutrino and electron pairs each second. In the tritium lab, special rules are in place because of the radioactivity — scientists enter via an air lock and must wash their hands when they leave. The place has a spaceship vibe, says Larisa Thorne, a physics graduate student at Carnegie Mellon University. “I did feel quite like I was on Star Trek.”

    Muon g-2

    Fermilab, Batavia, Ill.
    Approximate cost: $46 million

    6
    MOVING DAY A crane lifts the 50-ton apparatus containing Muon g-2’s magnetic ring, at the start of a cross-country journey to move the ring from Brookhaven National Laboratory in New York to Fermilab in Illinois. Brookhaven National Laboratory [ Muon g-2 started life at CERN]

    How it works

    Muons, heavier relatives of electrons, behave like tiny magnets with a north and south pole. Muon g-2, which started up in February, studies the properties of those minimagnets. Researchers beam thousands of muons into a doughnut-shaped electromagnet about as wide as the width of a basketball court. As muons circulate inside the electromagnet, their poles pivot like wobbling tops. Muons are unstable, so as they circulate, they decay into lighter particles known as positrons. The angles at which those positrons fly off can reveal the rate of the muons’ magnetic gyrations and, therefore, the strength of the muons’ magnets. The researchers will compare the measurement to predictions based on the standard model.

    ____________________________________________
    1. Muons enter the magnet.

    2. Muons circle in the same direction repeatedly.

    3. Muons decay into positrons, which are picked up by detectors that measure energy and particle tracks.
    [Image of the Muon G-2 studio at FNAL is above]

    ____________________________________________
    OK, but why?

    Transient particles blip in and out of existence everywhere in space. Those particles tweak the rate at which the muons gyrate. If undetected particles are out there, Muon g-2’s measurement might not square with predictions. A similar experiment performed at Brookhaven National Laboratory in Upton, N.Y., in the 1990s hinted at a mismatch (SN: 2/17/01, p. 102). Muon g-2 will make a more precise measurement to follow up on that lead.
    One ring

    Muon g-2’s magnetic field is about 30,000 times as strong as Earth’s magnetic field. Such strength is useful only if the magnetic field is ultrauniform. So physicists strategically placed thousands of tiny metal shims — many just a fraction of the thickness of notebook paper — to adjust the magnetic field. Hours of “shimming” left physicists’ hands “covered in dirt and oil and grease,” says physics graduate student Rachel Osofsky of the University of Washington in Seattle. The dirty job was worth it: The magnetic field is now uniform to within 0.0015 percent.

    See the full article here .


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  • richardmitnick 8:48 am on June 12, 2017 Permalink | Reply
    Tags: , , KEK Belle II SuperKEKB accelerator, , , Physicists review three experiments that hint at a phenomenon beyond the Standard Model of particle physics, ,   

    From phys.org: “Physicists review three experiments that hint at a phenomenon beyond the Standard Model of particle physics” 

    physdotorg
    phys.org

    June 8, 2017

    1
    Event display recorded by the BaBaR detector showing the decays of two B mesons into various subatomic particles, including a muon and a neutrino. Credit: SLAC NATIONAL ACCELERATOR LABORATORY

    To anyone but a physicist, it sounds like something out of “Star Trek.” But lepton universality is a real thing.

    It has to do with the Standard Model of particle physics, which describes and predicts the behavior of all known particles and forces, except gravity. Among them are charged leptons: electrons, muons and taus.

    A fundamental assumption of the Standard Model is that the interactions of these elementary particles are the same despite their different masses and lifetimes. That’s lepton universality. Precision tests comparing processes involving electrons and muons have not revealed any definite violation of this assumption, but recent studies of the higher-mass tau lepton have produced observations that challenge the theory.

    A new review of results from three experiments points to the strong possibility that lepton universality—and perhaps ultimately the Standard Model itself—may have to be revised. The findings by a team of international physicists, including UC Santa Barbara postdoctoral scholar Manuel Franco Sevilla, appear in the journal Nature.

    “As part of my doctoral thesis at Stanford, which was based on earlier work carried out at UCSB by professors Jeff Richman and Michael Mazur, we saw the first significant observation of something beyond the Standard Model at the BaBaR experiment conducted at the SLAC National Accelerator Laboratory,” Franco Sevilla said.

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

    SLAC BABAR

    This was significant but not definitive, he added, noting that similar results were seen in more recent experiments conducted in Japan (Belle) and in Switzerland (LHCb). According to Franco Sevilla, the three experiments, taken together, demonstrate a stronger result that challenges lepton universality at the level of four standard deviations, which indicates a 99.95 percent certainty.

    BaBaR, which stands for B-Bbar (anti-B) detector, and Belle were carried out in B factories. These particle colliders are designed to produce and detect B mesons—unstable particles that result when powerful particle beams collide—so their properties and behavior can be measured with high precision in a clean environment. The LHCb (Large Hadron Collider b) provided a higher-energy environment that more readily produced B mesons and hundreds of other particles, making identification more difficult.

    KEK Belle SuperKEKB accelerator

    CERN/LHCb

    Nonetheless, the three experiments, which measured the relative ratios of B meson decays, posted remarkably similar results. The rates for some decays involving the heavy lepton tau, relative to those involving the light leptons—electrons or muons—were higher than the Standard Model predictions.

    “The tau lepton is key because the electron and the muon have been well measured,” Franco Sevilla explained. “Taus are much harder because they decay very quickly. Now that physicists are able to better study taus, we’re seeing that perhaps lepton universality is not satisfied as the Standard Model claims.”

    While intriguing, the results are not considered sufficient to establish a violation of lepton universality. To overturn this long-held physics precept would require a significance of at least five standard deviations. However, Franco Sevilla noted, the fact that all three experiments observed a higher-than-expected tau decay rate while operating in different environments is noteworthy.

    A confirmation of these results would point to new particles or interactions and could have profound implications for the understanding of particle physics. “We’re not sure what confirmation of these results will mean in the long term,” Franco Sevilla said. “First, we need to make sure that they’re true and then we’ll need ancillary experiments to determine the meaning.”

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 9:29 pm on June 7, 2017 Permalink | Reply
    Tags: , , , Belle, , , KEK Belle II SuperKEKB accelerator, , , , Vera Lüth,   

    From SLAC: Women in STEM – “Q&A: SLAC’s Vera Lüth Discusses the Search for New Physics” 


    SLAC Lab

    June 7, 2017
    Manuel Gnida

    4
    Vera Lüth, professor emerita of experimental particle physics at SLAC. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Data from BABAR, Belle and LHCb experiments hint at phenomena beyond the Standard Model of particle physics.

    SLAC BABAR

    1
    An electron-positron annihilation producing a pair of B mesons as recorded by the BABAR detector at the PEP-II storage rings. Among the reconstructed curved particle tracks is a muon (bottom left). The direction of the associated anti-neutrino (dashed arrow) is identified as missing momentum. Both particles originate from the same B-meson decay. (SLAC National Accelerator Laboratory)

    KEK Belle detector, at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan

    CERN LHCb chamber, LHC

    The Standard Model of particle physics describes the properties and interactions of the constituents of matter.

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

    The development of this theory began in the early 1960s, and in 2012 the last piece of the puzzle was solved by the discovery of the Higgs boson at the Large Hadron Collider (LHC) at CERN in Switzerland.

    CERN CMS Higgs Event

    CERN ATLAS Higgs Event

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Experiments have confirmed time and again the Standard Model’s very accurate predictions.

    Yet, researchers have reasons to believe that physics beyond the Standard Model exists and should be found. For instance, the Standard Model does not explain why matter dominates over antimatter in the universe. It also does not provide clues about the nature of dark matter – the invisible substance that is five times more prevalent than the regular matter we observe.

    In this Q&A, particle physicist Vera Lüth discusses scientific results that potentially hint at physics beyond the Standard Model. The professor emerita of experimental particle physics at the Department of Energy’s SLAC National Accelerator Laboratory is co-author of a review article published today in Nature that summarizes the findings of three experiments: BABAR at SLAC, Belle in Japan and LHCb at CERN.

    What are the hints of new physics that you describe in your article?

    The hints originate from studies of an elementary particle, known as the B meson – an unstable particle produced in the collision of powerful particle beams. More precisely, these studies looked at decays of the B meson that involve leptons – electrically charged elementary particles and their associated neutrinos. There are three charged leptons: the electron, a critical component of atoms discovered in 1897; the muon, first observed in cosmic rays in 1937; and the much heavier tau, discovered at the SPEAR electron-positron (e+e-) storage ring at SLAC in 1975 by Martin Perl.

    Due to their very different masses, the three leptons also have very different lifetimes. The electron is stable, whereas the muon and tau decay in a matter of microseconds and a fraction of a picosecond, respectively. A fundamental assumption of the Standard Model is that the interactions of the three charged leptons are the same if their different masses and lifetimes are taken into account.

    Over many years, different experiments have tested this assumption – referred to as “lepton universality” – and to date no definite violation of this rule has been observed. We now have indications that the rates for B meson decays involving tau leptons are larger than expected compared to the measured rates of decays involving electrons or muons, taking into account the differences in mass. This observation would violate lepton universality, a fundamental assumption of the Standard Model.

    What does a violation of the Standard Model actually mean?

    It means that there is evidence for phenomena that we cannot explain in the context of the Standard Model. If such a phenomenon is firmly established, the Standard Model needs to be extended – by introducing new fundamental particles and also new interactions related to these particles.

    In recent years, searches for fundamentally new phenomena have relied on high-precision measurements to detect deviations from Standard Model predictions or on searches for new particles or interactions with properties that differ from known ones.

    What exactly are the BABAR, Belle and LHCb experiments?

    They are three experiments that have challenged lepton universality.

    Belle and BABAR were two experiments specifically designed to study B mesons with unprecedented precision – particles that are five times heavier than the proton and contain a bottom or b quark. These studies were performed at e+e- storage rings that are commonly referred to as B factories and operate at colliding-beam energies just high enough to produce a pair of B mesons, and no other particle. BABAR operated at SLAC’s PEP-II from 1999 to 2008, Belle at KEKB in Japan from 1999 to 2010. The great advantage of these experiments is that the B mesons are produced pairwise, each decaying into lighter particles – on average five charged particles and a similar number of photons.

    The LHCb experiment is continuing to operate at the proton-proton collider LHC with energies that exceed the ones of B factories by more than a factor of 1,000. At this higher energy, B mesons are produced at a much larger rate than at B factories. However, at each crossing of the beams, hundreds of other particles are produced in addition to B mesons. This feature tremendously complicates the identification of B meson decays.

    To study lepton universality, all three experiments focus on B decays involving a charged lepton and an associated neutrino. A neutrino doesn’t leave a trace in the detector, but its presence is detected as missing energy and momentum in an individual B decay.

    What evidence do you have so far for a potential violation of lepton universality?

    All three experiments have identified specific B meson decays and have compared the rates of decays involving an electron or muon to those involving the higher mass tau lepton. All three experiments observe higher-than-expected decay rates for the decays with a tau. The average value of the reported results, taking into account the statistical and systematic uncertainties, exceeds the Standard Model expectation by four standard deviations.

    This enhancement is intriguing, but not considered sufficient to unambiguously establish a violation of lepton universality. To claim a discovery, particle physicists generally demand a significance of at least five standard deviations. However, the fact that this enhancement was detected by three experiments, operating in very different environments, deserves attention. Nevertheless, more data will be needed, and are expected in the not too distant future.

    What was your role in this research?

    As the technical coordinator of the BABAR collaboration during the construction of the detector, I was the liaison between the physicists and the engineering teams, supported by the BABAR project management team at SLAC. With more than 500 BABAR members from 11 countries, this was a challenging task, but with the combined expertise and dedication of the collaboration the detector was completed and ready to take data in four years.

    Once data became available, I rejoined SLAC’s Research Group C and took over its leadership from Jonathan Dorfan. As convener of the physics working group on B decays involving leptons, I coordinated various analyses by scientists from different external groups, among them SLAC postdocs and graduate students, and helped to develop the analysis tools needed for precision measurements.

    Almost 10 years ago, we started updating an earlier analysis performed under the leadership of Jeff Richman of the University of California, Santa Barbara on B decays involving tau leptons and extended it to the complete BABAR data set. This resulted in the surprisingly large decay rate. The analysis was the topic of the PhD thesis of my last graduate student, Manuel Franco Sevilla, who over the course of four years made a number of absolutely critical contributions that significantly improved the precision of this measurement, and thereby enhanced its significance.

    What keeps you excited about particle physics?

    Over the past 50 years that I have been working in particle physics, I have witnessed enormous progress in theory and experiments leading to our current understanding of matter’s constituents and their interactions at the most fundamental level. But there are still many unanswered questions, from very basic ones like “Why do particles have certain masses and not others?” to questions about the grand scale of things, such as “What is the origin of the universe, and is there more than one?”

    Lepton universality is one of the Standard Model’s fundamental assumptions. If it were violated, unexpected new physics processes must exist. This would be a major breakthrough – even more surprising than the discovery of the Higgs boson, which was predicted to exist many decades ago.

    What results do you expect in the near future?

    There is actually a lot going on in the field. LHCb researchers are collecting more data and will try to find out if the lepton universality is indeed violated. My guess is that we should know the answer by the end of this year. A confirmation will be a great event and will undoubtedly trigger intense experimental and theoretical research.

    At present we do not understand the origin of the observed enhancement. We first assumed that it could be related to a charged partner of the Higgs boson. Although the observed features did not match the expectations, an extension of the Higgs model could do so. Another possible explanation that can neither be confirmed nor excluded is the presence of so-called lepto-quarks. These open questions will remain a very exciting topic that need to be addressed by experiments and theoretical work.

    Recently, LHCb scientists have reported an interesting result indicating that certain B meson decays more often include an electron pair than a muon pair. However, the significance of this new finding is only about 2.6 standard deviations, so it’s too early to draw any conclusions. BABAR and Belle have not confirmed this observation.

    At the next-generation B factory, Super-KEKB in Japan, the new Belle II experiment is scheduled to begin its planned 10-year research program in 2018. The expected very large new data sets will open up many opportunities for searches for these and other indications of physics beyond the Standard Model.

    4
    Super-KEKB in Japan

    5
    Belle II at the SuperKEKB accelerator complex at KEK in Tsukuba, Ibaraki Prefecture, Japan

    See the full article here .

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    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 5:08 pm on May 21, 2017 Permalink | Reply
    Tags: , , , KEK Belle II SuperKEKB accelerator, ,   

    From Interactions.org: “La Vie Est Belle” 

    Interactions.org

    16th May 2017
    Saurabh Sandilya

    1

    The field of ‘High Energy Physics’ or ‘Particle Physics’ is about exploring the fundamental building blocks of matter and interactions between them at the deepest level. The experimental frontier of this field relies on the cutting edge instrumentations and the most advanced computational tools. So, as an experimental high energy physicist, I am excited by the theoretical aspect as well as its experimental advancement is also overwhelming.

    I started my journey in this field seven years back with the Belle (‘french:beautiful’) experiment as a doctoral student at Tata Institute of Fundamental Research, Mumbai.

    KEK Belle 2 detector, in Tsukuba, Ibaraki Prefecture, Japan

    The Belle detector was located at the interaction region (beam collision point) of the KEKB asymmetric energy electron-positron collider in Tsukuba, Japan. And, the KEKB accelerator holds the current world-record for the luminosity achieved by a high-energy accelerator. The Belle experiment had a successful operational period with several important physics results, and the ‘Observation of CP Violation in B meson system’ led to the Nobel Prize in Physics 2008 to Profs. Kobayashi and Maskawa. The Belle detector recorded about 1 ab-1 data between 1999 – 2010, which continues to produce very competitive physics results. But, to explore the unknown territory of New Physics (beyond the Standard Model of Particle Physics) even more data is needed. For this, the KEKB accelerator is now being upgraded to SuperKEKB and it is designed to produce 40 times larger instantaneous luminosity than its predecessor and with the aim of recording an unprecedented data sample of 50 ab–1. And, to cope with this high collision rate environment, the detector is also being upgraded to Belle II.

    Although I got a very brief opportunity to work on the detector development for Belle II during my doctoral period, as my thesis was mainly focused on the physics data analysis for the Belle experiment. However, my desire to work on the instrumentation got fulfilled as a post-doctoral fellow in University of Cincinnati. I participated in the construction of time of propagation (TOP) detector, which plays a crucial role in identification of charged particles produced after the collision. The Belle II detector consists of several sub-detectors and TOP detector is one of them.

    Each sub-detector of the Belle II collects specific information about the collision event. Closest to the beam pipe is the Vertex Detector which consists of two-layers silicon pixel detector and then four-layers of double-sided silicon-strip detector and identifies the vertices (or decay points) of short lived particles (with lifetimes of around a trillionth of a second). Then, the Central Drift Chamber provides the momentum of charged particles by reconstructing their curved trajectories while moving in a magnetic field. Additionally, it contributes to particle identification by measuring the energy loss of charged particles as they pass through the gas that fills the volume. Aerogel Ring Imaging Cherenkov detector in the forward endcap region and TOP in central region of the detector provides charged particle identification based on angle of the cherenkov photon emitted by the charged particle passing through the detector medium. The The electromagnetic calorimeter reuses Belle’s thallium-doped cesium-iodide crystals with upgraded read-out electronics. And, the flux return of the Belle-II solenoid magnet, which surrounds the electromagnetic calorimeter, is instrumented to detect KL mesons and muons.

    In February 2016, electron and positron beams were successfully stored in the upgraded SuperKEKB accelerator for the first time.


    KEK Bell SuperKEKB accelerator.

    Now, most of the detectors are installed in the Belle II detector. And, on April 11th this year, the Belle II detector was rolled-in from its construction area to the interaction region of the SuperKEKB particle accelerator. The roll-in of the assembled Belle II detector, weighing 1,400 tons, has to be carried out very gently and with great care. And, this successful event was broadcasted live worldwide. Belle II is now getting ready in full swing to record the first collisions at the SuperKEKB scheduled at the end of this year.

    The Belle II collaboration has more than 600 members from 23 countries and this also provides a nice ground for cultural exchanges while interacting with colleagues from around the world. I really admire working in these large collaborations, as people go beyond the boundaries of geography, race and religion and come forward for a common goal ‘to extend the knowledge of mankind’. The sense of joy and thrill, while exploring together the recipe of our Universe as we see today, is unparalleled.

    See the full article here .

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