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  • richardmitnick 2:18 pm on June 18, 2017 Permalink | Reply
    Tags: Accelerator Science, , , First collisions of 2017 in ALICE: ready to go, , , ,   

    From ALICE: “First collisions of 2017 in ALICE: ready to go” 

    CERN
    CERN New Masthead

    16 June 2017
    Virginia Greco

    1
    No image caption or credit

    After the long winter shut-down, on May 23 the first proton-proton collisions with stable beams of 2017 were delivered by LHC and detected by the four experiments. The ALICE detector was fully operative and took great snapshots of these collisions (as the event display in the picture).

    The accelerator is now in the intensity ramp-up phase: it started injecting only few bunches and is gradually increasing the number in subsequent fills. It is expected to reach the nominal working conditions towards the beginning of July.

    In reality, the very first collisions were delivered a week before the official date, but they were not in optimal conditions, since the beams were not stable. During this phase, which is called ‘quiet beam’, the experts of LHC perform tests and make adjustments to the various components of the accelerator.

    ALICE used the quiet beam collisions to perform some performance tests, in particular on the forward detectors (AD, V0) and the Electro-Magnetic Calorimeter (EMCAL), but only a minor part of the whole apparatus was switched on. This is because the quiet beam is not totally safe for the instrumentation: when the experts of LHC change the settings of the machine and make adjustments, there is the risk of beam losses hitting directly the detectors, and thus damaging them. In particular, the parts that need to stay off are those closest to the beam line, such as parts of the inner tracking system and the gas detectors.

    When collisions with stable beams were delivered, ALICE started its data-taking programme. The LHC ramp-up plan started with three circulating bunches per beam, and moved on to about 12, 75, 300, 600.

    Even if at the beginning the collision rate was very low, a number of operations could be performed, such as a trigger alignment scan for the pixel detector and a high-voltage scan for the V0 and AD sub-detectors to find the optimal work voltage.

    In order to have precise information on the alignment of the central barrel detectors, data were taken with different polarities of the dipole and the solenoid (specifically, minus-minus, plus-plus and no magnetic fields). This information will be used to reconstruct the data that will be collected along the whole year.

    Following the requirements of some physics group, run of data taking at low rate – with the whole detector on – were also performed, as well as at high interaction rate (150kHz, the nominal one) with the Time Projection Chamber (TPC). This was particularly important, since during the shut-down the gas mixture filling the TPC was changed from Ar-CO2 to Ne- CO2-N2. In this test, the detector showed high performance, as expected.

    Finally, during the 300-bunches fill ALICE took data with a reduced (halved) magnetic field of the solenoid, since these conditions are recommended to study the low mass di-muon spectrum.

    “The restart has been great,” comments Grazia Luparello, run coordinator of ALICE, “in just a few fills of the accelerator we managed to perform all the tests and the special data taking included in our programme; we are satisfied and ready to go for physics”.

    See the full article here .

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    Meet CERN in a variety of places:

    CernCourier
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    THE FOUR MAJOR PROJECT COLLABORATIONS
    ATLAS
    CERN/ATLAS detector

    ALICE
    CERN ALICE New

    CMS
    CERN/CMS Detector

    LHCb

    CERN/LHCb

    LHC

    CERN/LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles


    Quantum Diaries

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

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

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    13th June 2017
    ATLAS Collaboration

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

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

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

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

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

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

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

    See the full article here .

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

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  • richardmitnick 2:53 pm on June 13, 2017 Permalink | Reply
    Tags: Accelerator Science, Bs meson, , , ,   

    From FNAL: “Bs matter-antimatter oscillations go at 3 trillion times a second” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    June 13, 2017
    Troy Rummler

    The Standard Model of physics makes some not-so-standard predictions about our universe.

    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.

    Fermilab has pioneered extremely precise technologies that put these theories to the test, including the CDF experiment, which confirmed in 2006 that, yes, a Bs (pronounced “B sub s”) meson actually does switch between matter and antimatter 3 trillion times a second.

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 1:11 pm on June 13, 2017 Permalink | Reply
    Tags: Accelerator Science, , , , , Two new teams of high-school physicists selected to run experiments at CERN   

    From CERN: “Two new teams of high-school physicists selected to run experiments at CERN” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    13 Jun 2017

    1
    The ” Charging Cavaliers” (on the left) and “TCO-ASA” (on the right).

    Geneva, 13 June 2017. CERN today announced the winners of its 2017 Beamline for Schools competition. “Charging Cavaliers” from Canada and “TCO-ASA” from Italy were selected from a total of 180 teams from 43 countries around the world, adding up to about 1500 high-school students. The winners have been selected to come to CERN in September to carry out their own experiments using a CERN accelerator beam.

    With the Beamline for Schools competition, high-school students are enabled to run an experiment on a fully-equipped CERN beamline, in the same way that researchers do at the Large Hadron Collider and other CERN facilities. Students had to submit a written proposal and video explaining why they wanted to come to CERN, what they hoped to take away from the experience and initial thoughts of how they would use the particle beam for their experiment. Taking into consideration creativity, motivation, feasibility and scientific method, CERN experts evaluated the proposals. A final selection was presented to the CERN scientific committee responsible for assigning beam time to experiments, who chose two winning teams to carry out their experiments together at CERN.

    “The quality and creativity of the proposals is inspiring. It shows the remarkable talent and commitment of the new generation of potential scientists and engineers. I congratulate all who have taken part this year; they can all be proud of their achievements. We very much look forward to welcoming the two winning teams and seeing the outcome of their experiments,” said CERN Director for International Relations, Charlotte Warakaulle.

    “Charging Cavaliers” are thirteen students (6 boys and 7 girls) from the “École secondaire catholique Père-René-de-Galinée” in Cambridge, Canada. Their project is the search for elementary particles with a fractional charge, by observing their light emission in the same type of liquid scintillator as that used in the SNO+ experiment at SNOLAB. With this proposal, they are questioning the Standard Model of particle physics and trying to get a glimpse at a yet unexplored territory.

    “I still can’t believe what happened. I feel incredibly privileged to be given this opportunity. It’s a once a lifetime opportunity It opens so many doors to a knowledge otherwise inaccessible to me. It represents the hard work our team has done. There’s just no words to describe it. Of course, I’m looking forward to putting our theory into practice in the hope of discovering fractionally charged particles, but most of all to expanding my knowledge of physics.” said Denisa Logojan from the Charging Cavaliers.

    “TCO-ASA” is a team from the “Liceo Scientifico Statale “T.C. Onesti”” in Fermo, Italy, and comprises 8 students (6 boys and 2 girls). They have taken the initiative to build a Cherenkov detector at their school. This detector has the potential of observing the effects of elementary particles moving faster than light does in the surrounding medium. Their plan is to test this detector, which is entirely made from low-cost and easily available materials, in the beam line at CERN.

    “I’m really excited about our win, because I’ve never had an experience like this. Fermo is a small city and I’ve never had the opportunity to be in a physics laboratory with scientists that study every day to discover something new. I think that this experience will bring me a bit closer to my choices for my future” said Roberta Barbieri from TCO-ASA team.

    The first Beamline for Schools competition was launched three years ago on the occasion of CERN’s 60th anniversary. To date, winners from the Netherlands, Greece, Italy, South Africa Poland and the United Kingdom have performed their experiments at CERN. This year, short-listed teams[1] each receive a Cosmic-Pi detector for their school that will allow them to detect cosmic-ray particles coming from outer space.

    “After four editions, the Beamline for Schools competition has well established itself as an important outreach and education activity of CERN. This competition has the power to inspire thousands of young and curious minds to think about the role of science and technology in our society. Many of the proposals that we have received this year would have merited an invitation to CERN.”, said Markus Joos, Beamline for School project leader.

    Beamline for Schools is an education and outreach project supported by the CERN & Society Foundation, funded by individuals, foundations and companies.

    The project was funded in 2017 in part by the Arconic Foundation; additional contributions were received by the Motorola Solutions Foundation, as well as from National Instruments. CERN would like to thank all the supporters for their generous contributions that have made the 2017 competition possible.

    Beamline for schools 2018 is confirmed: you can already find information here.

    Further information:

    Team “TCO-ASA”: Extract from their proposal “In BL4S 2016 the proposal of our school received the status of highly commended, which really intrigued us. The basic idea is to achieve an authentic detector by using some simple instruments. We wanted to study the Cherenkov’s effect that is radiation emitted when a charged particle passes through a dielectric medium at a speed greater than the phase velocity of light in that medium. […]This year we made a new box with new sensors and we started the tests on the Cherenkov’s effect from the beginning. Our research gave us satisfying results with which we hope to win the BL4S 2017 competition. […]”

    Team “Charging Cavaliers”: Extract from their proposal “Generally, the idea that electric charge exists in integer multiples of electron charges is well supported by the scientific community. Be that as it may, the Standard Model, which includes three generations of quarks and leptons, does not establish charge quantization. To be able to enforce charge quantization, physics beyond the limits of the Standard Model is imperative. […] Our experiment will search for fractionally charged particles using proton interactions at the Proton Synchrotron with the goal of identifying fractionally charged particles by observing their light emission in a liquid scintillator, comparatively to a conventionally charged particle. […] It is our duty to encourage the pursuit of knowledge, and beginning with this privileged occasion would only advocate for this cause. We must think forward, and this would be our first big step toward doing so.”

    1. A.O.C group from Israel Absolute Uncertainty from the United Kingdom Beamcats from the Philippines Bojos per la Física 2017 from Spain Brazinga from Brazil Cherenkov Radiation Busters from Poland Club de Física Enrico Fermi from Spain CURIEosity Team from Greece Dawson Technicolor from Canada Deep Impact from Chile DITI – Deep In The Ice from Poland G-Y-V-V Amavet 964 from Slovakia Hildebrandianer from Germany LEAM TEAM – Learning About Materials Team from Timor-Leste Newton’s apples from Spain Pigeon Detectors from the United Kingdom P.R.O.ME.THE.U.S from Italy Q=MC² from the United Kingdom Salty Brits from the United Kingdom Sparticles Particles 2.0 from the United States Surfing the Wave Function from the United States Team Hephaestus from India Team Muonicity from India Terrella from New Zealand THE BIG BANG TEAM from Italy United World Astronauts from the Netherlands Vacuum Dunes from Spain Y=GC2 from the United Kingdom

    See the full article here.

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    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    CernCourier
    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
  • richardmitnick 8:48 am on June 12, 2017 Permalink | Reply
    Tags: Accelerator Science, , , , , 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 12:11 pm on June 10, 2017 Permalink | Reply
    Tags: Accelerator Science, , , , , , Tevatron first accelerator to use electron lens   

    From FNAL: “Tevatron first accelerator to use electron lens” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    accelerator to use electron lens

    June 10, 2017
    Troy Rummler
    1

    Tevatron is the first accelerator to use an electron lens

    Fermilab’s Tevatron was the first particle accelerator to make use of an electron lens, a technique that allowed the machine to compensate for destabilizing forces unavoidably generated by the colliding beams. Proposed in 1997, the lenses were installed in 2001 and 2004 in the Tevatron, where they demonstrated beam-beam compensation. They were also used in the removal of unwanted particles. The innovation earned Fermilab scientist Vladimir Shiltsev a European Physical Society Accelerator Prize.

    FNAL Tevatron

    FNAL/Tevatron map


    FNAL/Tevatron DZero detector


    FNAL/Tevatron CDF detector

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 11:26 am on June 8, 2017 Permalink | Reply
    Tags: Accelerator Science, , CDF rounds up the final meson, , , , ,   

    From FNAL: “CDF rounds up the final meson” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    June 8, 2017
    Troy Rummler

    1
    FNAL Tevatron CDF

    On March 5, 1998, Fermilab announced it had discovered the Bc meson. This particle was the last of 15 unexcited quark-antiquark pairs to be discovered. The first one had been discovered 50 years earlier in cosmic rays, but this flighty character, which lives just 0.46 picoseconds, could be found only as a product of powerful, high-energy particle collisions.

    See the full article here .

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    FNAL Icon
    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 9:29 pm on June 7, 2017 Permalink | Reply
    Tags: Accelerator Science, , , Belle, , , , , , , 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 Campus
    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 1:17 pm on June 6, 2017 Permalink | Reply
    Tags: Accelerator Science, , , , , , When proton–proton collisions turn strange   

    From Physics Today: “When proton–proton collisions turn strange” 

    Physics Today bloc

    Physics Today

    5 Jun 2017
    Sung Chang

    Enhanced production of particles that contain strange quarks deepens the mysteries surrounding the formation of a quark–gluon plasma.

    1
    Protons colliding into other protons at CERN’s Large Hadron Collider (LHC) flushed out the Higgs boson.

    CERN CMS Higgs Event

    CERN ATLAS Higgs Event

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    But for studying quark–gluon plasma (QGP)—the hot, dense soup of unconfined quarks and gluons that briefly filled the universe a few microseconds after the Big Bang—those collisions were supposed to be irrelevant. They are even used as QGP-absent baselines to compare with when investigating heavy-ion collisions that do produce QGP. However, in 2010 the CMS collaboration spotted something unexpected in proton–proton collisions. In the debris of rare, so-called high-multiplicity events—that is, events that produce an unusually high number of charged particles—the researchers discovered spatial correlations reminiscent of those attributed to QGP formation in heavy-ion collisions (see the article by Barbara Jacak and Peter Steinberg, Physics Today, May 2010, page 39). The ALICE and ATLAS collaborations soon corroborated the discovery.

    In addition, ALICE researchers found that in proton–lead ion collisions, the relative yield of particles that contain strange quarks increases with multiplicity. Strangeness enhancement is another hallmark of QGP formation. Now the ALICE collaboration reports that in high-multiplicity proton–proton collisions, such as the one shown here, strangeness is similarly enhanced. The finding is the latest entry in a growing, though not yet conclusive, list of evidence that QGP can form even in proton–proton collisions. Now that the LHC is operating at higher energies, the high-multiplicity collisions are both more frequent and extend to higher multiplicities. Researchers hope to decisively establish whether QGP can indeed be created in proton–proton collisions. And if that’s the case, physicists could probe the properties of QGP in a far simpler system than the one produced in heavy-ion collisions. (J. Adam et al., ALICE collaboration, Nat. Phys. 13, 535, 2017. Image courtesy of CERN.)

    See the full article here .

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    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 2:28 pm on June 3, 2017 Permalink | Reply
    Tags: Accelerator Science, , , Kiyomi Seiya, , , Slip stacking   

    From FNAL: “Fermilab is first to successfully implement slip stacking for accelerating beams” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    June 3, 2017
    Troy Rummler

    1

    The Fermilab accelerator complex smashes protons into so-called targets to produce other particles that scientists can study. The more protons the accelerator can provide, the more data there is to work with. Fermilab accelerator scientists and engineers were the first to successfully implement a technique called “slip stacking,” which allows the injection of multiple batches of beams into an accelerator at one time. By implementing slip stacking, Fermilab effectively doubled the number of protons delivered by its Main Injector accelerator. Kiyomi Seiya was given an IEEE Particle Accelerator Science and Technology award for the work.

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
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