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  • richardmitnick 11:26 am on November 8, 2017 Permalink | Reply
    Tags: , , , , , , , SLAC BaBar   

    From LBNL: “New Study: Scientists Narrow Down the Search for Dark Photons Using Decade-Old Particle Collider Data” 

    Berkeley Logo

    Berkeley Lab

    November 8, 2017
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 520-0843

    1
    The BaBar detector at SLAC National Accelerator Laboratory. (Credit: SLAC)

    SLAC BABAR

    In its final years of operation, a particle collider in Northern California was refocused to search for signs of new particles that might help fill in some big blanks in our understanding of the universe.

    A fresh analysis of this data, co-led by physicists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), limits some of the hiding places for one type of theorized particle – the dark photon, also known as the heavy photon – that was proposed to help explain the mystery of dark matter.

    The latest result, published in the journal Physical Review Letters by the roughly 240-member BaBar Collaboration, adds to results from a collection of previous experiments seeking, but not yet finding, the theorized dark photons.

    “Although it does not rule out the existence of dark photons, the BaBar results do limit where they can hide, and definitively rule out their explanation for another intriguing mystery associated with the property of the subatomic particle known as the muon,” said Michael Roney, BaBar spokesperson and University of Victoria professor.

    Dark matter, which accounts for an estimated 85 percent of the total mass of the universe, has only been observed by its gravitational interactions with normal matter. For example, the rotation rate of galaxies is much faster than expected based on their visible matter, suggesting there is “missing” mass that has so far remained invisible to us.

    So physicists have been working on theories and experiments to help explain what dark matter is made of – whether it is composed of undiscovered particles, for example, and whether there may be a hidden or “dark” force that governs the interactions of such particles among themselves and with visible matter. The dark photon, if it exists, has been put forward as a possible carrier of this dark force.

    Using data collected from 2006 to 2008 at SLAC National Accelerator Laboratory in Menlo Park, California, the analysis team scanned the recorded byproducts of particle collisions for signs of a single particle of light – a photon – devoid of associated particle processes.

    The BaBar experiment, which ran from 1999 to 2008 at SLAC, collected data from collisions of electrons with positrons, their positively charged antiparticles. The collider driving BaBar, called PEP-II, was built through a collaboration that included SLAC, Berkeley Lab, and Lawrence Livermore National Laboratory. At its peak, the BaBar Collaboration involved over 630 physicists from 13 countries.

    BaBar was originally designed to study the differences in the behavior between matter and antimatter involving a b-quark. Simultaneously with a competing experiment in Japan called Belle, BaBar confirmed the predictions of theorists and paved the way for the 2008 Nobel Prize.

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

    Berkeley Lab physicist Pier Oddone proposed the idea for BaBar and Belle in 1987 while he was the Lab’s Physics division director.

    The latest analysis used about 10 percent of BaBar’s data – recorded in its final two years of operation. Its data collection was refocused on finding particles not accounted for in physics’ Standard Model – a sort of rulebook for what particles and forces make up the known universe.

    “BaBar performed an extensive campaign searching for dark sector particles, and this result will further constrain their existence,” said Bertrand Echenard, a research professor at Caltech who was instrumental in this effort.

    2
    This chart shows the search area (green) explored in an analysis of BaBar data where dark photon particles have not been found, compared with other experiments’ search areas. The red band shows the favored search area to determine whether dark photons are causing the so-called “g-2 anomaly,” and the white areas are among the unexplored territories for dark photons. (Credit: Muon g-2 Collaboration)

    In its final years of operation, a particle collider in Northern California was refocused to search for signs of new particles that might help fill in some big blanks in our understanding of the universe.

    A fresh analysis of this data, co-led by physicists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), limits some of the hiding places for one type of theorized particle – the dark photon, also known as the heavy photon – that was proposed to help explain the mystery of dark matter.

    The latest result, published in the journal Physical Review Letters by the roughly 240-member BaBar Collaboration, adds to results from a collection of previous experiments seeking, but not yet finding, the theorized dark photons.

    “Although it does not rule out the existence of dark photons, the BaBar results do limit where they can hide, and definitively rule out their explanation for another intriguing mystery associated with the property of the subatomic particle known as the muon,” said Michael Roney, BaBar spokesperson and University of Victoria professor.

    Dark matter, which accounts for an estimated 85 percent of the total mass of the universe, has only been observed by its gravitational interactions with normal matter. For example, the rotation rate of galaxies is much faster than expected based on their visible matter, suggesting there is “missing” mass that has so far remained invisible to us.

    So physicists have been working on theories and experiments to help explain what dark matter is made of – whether it is composed of undiscovered particles, for example, and whether there may be a hidden or “dark” force that governs the interactions of such particles among themselves and with visible matter. The dark photon, if it exists, has been put forward as a possible carrier of this dark force.

    Using data collected from 2006 to 2008 at SLAC National Accelerator Laboratory in Menlo Park, California, the analysis team scanned the recorded byproducts of particle collisions for signs of a single particle of light – a photon – devoid of associated particle processes.

    The BaBar experiment, which ran from 1999 to 2008 at SLAC, collected data from collisions of electrons with positrons, their positively charged antiparticles. The collider driving BaBar, called PEP-II, was built through a collaboration that included SLAC, Berkeley Lab, and Lawrence Livermore National Laboratory. At its peak, the BaBar Collaboration involved over 630 physicists from 13 countries.

    BaBar was originally designed to study the differences in the behavior between matter and antimatter involving a b-quark. Simultaneously with a competing experiment in Japan called Belle, BaBar confirmed the predictions of theorists and paved the way for the 2008 Nobel Prize. Berkeley Lab physicist Pier Oddone proposed the idea for BaBar and Belle in 1987 while he was the Lab’s Physics division director.

    The latest analysis used about 10 percent of BaBar’s data – recorded in its final two years of operation. Its data collection was refocused on finding particles not accounted for in physics’ Standard Model – a sort of rulebook for what particles and forces make up the known universe.

    “BaBar performed an extensive campaign searching for dark sector particles, and this result will further constrain their existence,” said Bertrand Echenard, a research professor at Caltech who was instrumental in this effort.
    Chart – This chart shows the search area (green) explored in an analysis of BaBar data where dark photon particles have not been found, compared with other experiments’ search areas. The red band shows the favored search area to determine whether dark photons are causing the so-called “g-2 anomaly,” and the white areas are among the unexplored territories for dark photons. (Credit: Muon g-2 Collaboration)

    This chart shows the search area (green) explored in an analysis of BaBar data where dark photon particles have not been found, compared with other experiments’ search areas. The red band shows the favored search area to determine whether dark photons are causing the so-called “g-2 anomaly,” and the white areas are among the unexplored territories for dark photons. (Credit: Muon g-2 Collaboration)

    Yury Kolomensky, a physicist in the Nuclear Science Division at Berkeley Lab and a faculty member in the Department of Physics at UC Berkeley, said, “The signature (of a dark photon) in the detector would be extremely simple: one high-energy photon, without any other activity.”

    A number of the dark photon theories predict that the associated dark matter particles would be invisible to the detector. The single photon, radiated from a beam particle, signals that an electron-positron collision has occurred and that the invisible dark photon decayed to the dark matter particles, revealing itself in the absence of any other accompanying energy.

    When physicists had proposed dark photons in 2009, it excited new interest in the physics community, and prompted a fresh look at BaBar’s data. Kolomensky supervised the data analysis, performed by UC Berkeley undergraduates Mark Derdzinski and Alexander Giuffrida.

    “Dark photons could bridge this hidden divide between dark matter and our world, so it would be exciting if we had seen it,” Kolomensky said.

    The dark photon has also been postulated to explain a discrepancy between the observation of a property of the muon spin and the value predicted for it in the Standard Model. Measuring this property with unprecedented precision is the goal of the Muon g-2 (pronounced gee-minus-two) Experiment at Fermi National Accelerator Laboratory [FNAL].

    FNAL G-2 magnet from Brookhaven Lab finds a new home in the FNAL Muon G-2 experiment

    FNAL Muon g-2 studio

    Earlier measurements at Brookhaven National Laboratory had found that this property of muons – like a spinning top with a wobble that is ever-slightly off the norm – is off by about 0.0002 percent from what is expected. Dark photons were suggested as one possible particle candidate to explain this mystery, and a new round of experiments begun earlier this year should help to determine whether the anomaly is actually a discovery.

    The latest BaBar result, Kolomensky said, largely “rules out these dark photon theories as an explanation for the g-2 anomaly, effectively closing this particular window, but it also means there is something else driving the g-2 anomaly if it’s a real effect.”

    It’s a common and constant interplay between theory and experiments, with theory adjusting to new constraints set by experiments, and experiments seeking inspiration from new and adjusted theories to find the next proving grounds for testing out those theories.

    Scientists have been actively mining BaBar’s data, Roney said, to take advantage of the well-understood experimental conditions and detector to test new theoretical ideas.

    “Finding an explanation for dark matter is one of the most important challenges in physics today, and looking for dark photons was a natural way for BaBar to contribute,” Roney said, adding that many experiments in operation or planned around the world are seeking to address this problem.

    An upgrade of an experiment in Japan that is similar to BaBar, called Belle II, turns on next year. “Eventually, Belle II will produce 100 times more statistics compared to BaBar,” Kolomensky said. “Experiments like this can probe new theories and more states, effectively opening new possibilities for additional tests and measurements.”

    “Until Belle II has accumulated significant amounts of data, BaBar will continue for the next several years to yield new impactful results like this one,” Roney said.

    The study featured participation by the international BaBar collaboration, which includes researchers from about 66 institutions in the U.S., Canada, France, Spain, Italy, Norway, Germany, Russia, India, Saudi Arabia, U.K., the Netherlands, and Israel. The work was supported by the U.S. Department of Energy’s Office of Science and the National Science Foundation; the Natural Sciences and Engineering Research Council in Canada; CEA and CNRS-IN2P3 in France; BMBF and DFG in Germany; INFN in Italy; FOM in the Netherlands; NFR in Norway; MES in Russia; MINECO in Spain; STFC in the U.K.; and BSF in Israel and the U.S. Individuals involved with this study have received support from the Marie Curie EIF in the European Union, and the Alfred P. Sloan Foundation in the U.S.

    See the full article here .

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  • richardmitnick 4:03 pm on August 24, 2017 Permalink | Reply
    Tags: , , , , , , , , , SLAC BaBar, SURF LBNF/ DUNE,   

    From Symmetry: “Mega-collaborations for scientific discovery” 

    Symmetry Mag

    Symmetry

    08/24/17
    Leah Poffenberger

    1
    DUNE joins the elite club of physics collaborations with more than 1000 members. Photo by Reidar Hahn, Fermilab.

    Sometimes it takes lot of people working together to make discovery possible. More than 7000 scientists, engineers and technicians worked on designing and constructing the Large Hadron Collider at CERN, and thousands of scientists now run each of the LHC’s four major experiments.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Not many experiments garner such numbers. On August 15, the Deep Underground Neutrino Experiment (DUNE) became the latest member of the exclusive clique of particle physics experiments with more than a thousand collaborators.

    Meet them all:

    3

    4,000+: Compact Muon Solenoid Detector (CMS) Experiment

    CMS is one of the two largest experiments at the LHC. It is best known for its role in the discovery of the Higgs boson.

    The “C” in CMS stands for compact, but there’s nothing compact about the CMS collaboration. It is one of the largest scientific collaborations in history. More than 4000 people from 200 institutions around the world work on the CMS detector and use its data for research.

    About 30 percent of the CMS collaboration hail from US institutions*. A remote operations center at the Department of Energy’s Fermi National Accelerator Laboratory in Batavia, Illinois, serves as a base for CMS research in the United States.

    4

    3,000+: A Toroidal LHC ApparatuS (ATLAS) Experiment

    The ATLAS experiment, the other large experiment responsible for discovering the Higgs boson at the LHC, ranks number two in number of collaborators. The ATLAS collaboration has more than 3000 members from 182 institutions in 38 countries. ATLAS and CMS ask similar questions about the building blocks of the universe, but they look for the answers with different detector designs.

    About 30 percent of the ATLAS collaboration are from institutions in the United States*. Brookhaven National Laboratory in Upton, New York, serves as the US host.

    2,000+: Linear Collider Collaboration

    Proposed LC Linear Collider schematic. Location not yet decided.

    The Linear Collider Collaboration (LCC) is different from CMS and ATLAS in that the collaboration’s experiment is still a proposed project and has not yet been built. LCC has around 2000 members who are working to develop and build a particle collider that can produce different kinds of collisions than those seen at the LHC.

    LCC members are working on two potential linear collider projects: the compact linear collider study (CLIC) at CERN and the International Linear Collider (ILC) in Japan. CLIC and the ILC originally began as separate projects, but the scientists working on both joined forces in 2013.

    Either CLIC or the ILC would complement the LHC by colliding electrons and positrons to explore the Higgs particle interactions and the nature of subatomic forces in greater detail.

    1,500+; A Large Ion Collider Experiment (ALICE)

    5

    ALICE is part of LHC’s family of particle detectors, and, like ATLAS and CMS, it too has a large, international collaboration, counting 1500 members from 154 physics institutes in 37 countries. Research using ALICE is focused on quarks, the sub-atomic particles that make up protons and neutrons, and the strong force responsible for holding quarks together.

    1,000+: Deep Underground Neutrino Experiment (DUNE)

    The Deep Underground Neutrino Experiment is the newest member of the club. This month, the DUNE collaboration surpassed 1000 collaborators from 30 countries.

    From its place a mile beneath the earth at the Sanford Underground Research Facility in South Dakota, DUNE will investigate the behavior of neutrinos, which are invisible, nearly massless particles that rarely interact with other matter. The neutrinos will come from Fermilab, 800 miles away.

    Neutrino research could help scientists answer the question of why there is an imbalance between matter and antimatter in the universe. Groundbreaking for DUNE occurred on July 21, and the experiment will start taking data in around 2025.

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA


    FNAL DUNE Argon tank at SURF


    Surf-Dune/LBNF Caverns at Sanford



    SURF building in Lead SD USA

    Honorable mentions

    A few notable collaborations have made it close to 1000 but didn’t quite make the list. LHCb, the fourth major detector at LHC, boasts a collaboration 800 strong.

    CERN/LHCb

    Over 700 collaborators work on the Belle II experiment at KEK in Japan, which will begin taking data in 2018, studying the properties of B mesons, particles that contain a bottom quark.

    Belle II super-B factory experiment takes shape at KEK
    5

    The 600-member SLAC/Babar collaboration at SLAC National Accelerator Laboratory also studies B mesons.

    SLAC/Babar

    STAR, a detector at Brookhaven National Laboratory that probes the conditions of the early universe, has more than 600 collaborators from 55 institutions.

    BNL/RHIC Star Detector

    The CDF and DZero collaborations at Fermilab, best known for their co-discovery of the top quark in 1995, had about 700 collaborators at their peak.

    FNAL/Tevatron DZero detector

    FNAL/Tevatron CDF detector

    *Among the reasons why I started this blog was that this level of U.S. involvement was invisible in our highly vaunted press. CERN had taken over HEP from FNAL. Our idiot Congress in 1993 had killed off the Superconducting Super Collider. So it looked like we had given up. But BNL had 600 people on ATLAS. FNAL had 1000 people on CMS. So we were far from dead in HEP, just invisible. So, I had a story to tell. Today I have 1000 readers. Not too shabby for Basic and Applied Science.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


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

    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 7:38 pm on October 14, 2014 Permalink | Reply
    Tags: , , , , , , , SLAC BaBar   

    From New Scientist vis FNAL: “Two new strange and charming particles appear at LHC” 

    NewScientist

    New Scientist

    08 October 2014
    Nicola Jenner

    Two new particles have been discovered by the LHCb experiment at CERN’s Large Hadron Collider near Geneva, Switzerland. One of them has a combination of properties that has never been observed before.

    CERN LHCb New
    LHCb

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

    The particles, named DS3*(2860)– and DS1*(2860)–, are about three times as massive as protons.

    Physicists analyzed LHCb observations of an energy peak that had been spotted in 2006 by the BaBar experiment at Stanford University in California, but whose cause was still unknown.

    “Our result shows that the BaBar peak is caused by two new particles,” says Tim Gershon of Warwick University, UK, lead author of the discovery.
    The force is strong

    Mesons are particles that contain two quarks – subatomic particles that make up matter and are thought to be indivisible. These quarks are bound together by the strong force, one of the four fundamental forces that also keeps the constituents of nuclei together within atoms. This force is one of the less well-understood parts of the standard model of particle physics, the incomplete theory that describes how particles interact.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Quarks come in six different flavours known as up, down, strange, charm, bottom and top, in order from lightest to heaviest. The new particles each contain one charm antiquark and one strange quark.

    Significantly, DS3*(2860)– also has a spin value of 3, making this discovery the first ever observation of a spin-3 particle containing a charm quark.

    In other mesons, the quarks can be configured in one of several different ways to give the particle an overall spin value less than three, and this makes the quarks’ exact properties ambiguous. However, for a spin value of three there is no such ambiguity, making DS3*(2860)–’s precise configuration clear.

    Combined with the particle’s charm quark, this may make DS3*(2860)– a key player for exploring the strong force, because the calculations involved are more straightforward for heavy quarks than for lighter ones.

    The LHCb team used a technique known as Dalitz plot analysis to untangle the data peak into its two components, a complex technique that had never before been used on LHC data.

    The technique helps separate and visualise the different paths a particle can take as it decays. Now that it has been used successfully on the LHCb dataset, says Gershon, it can hopefully be applied to more LHC data to help discover further particles and understand how they are bound together.

    “This is a lovely piece of experimental physics,” says Robert Jaffe of the Massachusetts Institute of Technology in Cambridge. “Although it doesn’t probe the limits of the standard model, it may shine light on the dynamics of quarks and gluons. The fact that LHCb was able to use Dalitz plot methods is a testimony to the quantity and high quality of the data they’ve accumulated. We can look forward to other similar discoveries in the future using this method.”

    See the full article here.

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  • richardmitnick 2:54 pm on February 18, 2014 Permalink | Reply
    Tags: , , SLAC BaBar,   

    From Symmetry: “BaBar still breaking new ground” 

    February 18, 2014
    Lori Ann White

    Twenty years after a cutting-edge particle physics experiment at SLAC adopted a royal elephant from a series of children’s books as its mascot, BaBar (the experiment, not the elephant) is still looking ahead to future discoveries.

    SLAC Babar
    BaBar

    In the two decades since its formal inception, the particle physics experiment known as BaBar has gone far beyond its original scientific goal: studying charge-parity violation, which is one method the universe uses to play favorites by showing a preference for matter over antimatter.

    But the agenda of BaBar’s 20th anniversary collaboration meeting in Frascati, Italy, last December, did not consist of three days of researchers patting themselves on the back. They were too busy preparing further data analyses and future proposals.

    BaBar Spokesman Michael Roney, a particle physics professor from the University of Victoria, says that the hundreds of scientists who have belonged to the international collaboration have published more than 500 scientific papers in the past two decades, discussing everything from newly discovered types of mesons (a particle made of a quark and an antiquark) to coming to grips with Big Data before it even had a name.

    The one thing they haven’t done is combine their data with data from their competition, Belle, a Japanese experiment that ran at the same time and also provided valuable data about charge-parity violation.

    Until now.

    The term competition is a little strong, says Roney: Having two different experiments pursue the same goal is a vital part of the scientific process. “Originally, it was important for Belle and BaBar to maintain their independence from each other so each experiment could serve as a check on the other,” he says. “But there are certain issues where neither experiment has enough data to make a definitive statement.”

    To solve that problem, Markus Röhrken, a post-graduate researcher at the California Institute of Technology and a relatively new BaBar-ian, will bring the Belle and BaBar datasets together for the first time. He’s on a hunt for aspects of charge-parity violation that could yield totally new physics beyond the Standard Model.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Combining the data is more complicated than it sounds. “The physics behind BaBar and Belle is exactly the same,” Röhrken says, “but the detectors, the software, the experiments themselves are very different.” Roehrken must become expert in both experiments; while he was a graduate student at Karlsruhe Institute of Technology in Germany, his PhD work was done on Belle, so he’s already half-way there.

    “It’s very unusual for two different collaborations to combine the data itself for analyses,” Roney says. “It’s much more common to combine published results.”

    But Röhrken has his own motivations for pursuing this. Japan is planning a follow-up to Belle, Belle 2, but it isn’t scheduled to start taking data until 2016 at the earliest.

    “I didn’t want to just wait for four or five years to work on these questions,” he says. “I want to look for new physics.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.



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  • richardmitnick 2:08 pm on November 19, 2012 Permalink | Reply
    Tags: , , , , , SLAC BaBar   

    From SLAC: “BaBar Experiment Confirms Time Asymmetry” 

    “Time marches relentlessly forward for you and me; watch a movie in reverse, and you’ll quickly see something is amiss. But from the point of view of a single, isolated particle, the passage of time looks the same in either direction. For instance, a movie of two particles scattering off of each other would look just as sensible in reverse – a concept known as time reversal symmetry.

    Now the BaBar experiment at the Department of Energy’s (DOE) SLAC National Accelerator Laboratory has made the first direct observation of a long-theorized exception to this rule.

    babar
    BaBar

    Digging through nearly 10 years of data from billions of particle collisions, researchers found that certain particle types change into one another much more often in one way than they do in the other, a violation of time reversal symmetry and confirmation that some subatomic processes have a preferred direction of time.

    Reported this week in the journal Physical Review Letters, the results are impressively robust, with a 1 in 10 tredecillion (1043) or 14-sigma level of certainty – far more than needed to declare a discovery.

    ‘It was exciting to design an experimental analysis that enabled us to observe, directly and unambiguously, the asymmetrical nature of time,’ said BaBar collaborator Fernando Martínez-Vidal, associate professor at the University of Valencia and member of the Instituto de Fisica Corpuscular (IFIC), who led the investigation. ‘This is a sophisticated analysis, the kind of experimental work that can only be done when an experiment is mature.’”

    See the full article here.

    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 1:47 pm on June 18, 2012 Permalink | Reply
    Tags: , , , , SLAC BaBar   

    From SLAC Today: “BaBar Data Hint at Cracks in the Standard Model” 

    June 18, 2012
    Lori Ann White

    “Recently analyzed data from the BaBar experiment may suggest possible flaws in the Standard Model of particle physics, the reigning description of how the universe works on subatomic scales. The data from BaBar, a high-energy physics experiment based at SLAC, show that a particular type of particle decay called “B to D-star-tau-nu” happens more often than the Standard Model says it should.


    Standard Model with the hypothetical Higgs boson

    In this type of decay, a particle called the B-bar meson decays into a D meson, an antineutrino and a tau lepton. While the level of certainty of the excess (3.4 sigma in statistical language) is not enough to claim a break from the Standard Model, the results are a potential sign of something amiss and are likely to impact existing theories, including those attempting to deduce the properties of Higgs bosons.


    Babar

    ‘The excess over the Standard Model prediction is exciting,’ said BaBar spokesperson Michael Roney, professor at the University of Victoria in Canada. The results are significantly more sensitive than previously published studies of these decays, said Roney. ‘But before we can claim an actual discovery, other experiments have to replicate it and rule out the possibility this isn’t just an unlikely statistical fluctuation.'”

    How cool is this!! See the full article here.

    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 12:35 pm on February 14, 2012 Permalink | Reply
    Tags: , , , SLAC BaBar   

    From SLAC Today: “SLAC Physicists Build Prototype of Particle Identification Detector” 

    February 14, 2012
    Lori Ann White

    “The technology behind the photon camera at the heart of BaBar’s Detection of Internally Reflected Cherenkov light (DIRC) detector is getting an upgrade thanks to Jaroslav (Jerry) Va’vra, SLAC detector physicist. With help from Italian mechanical engineer Massimo Benettoni and SLAC technician Matt McCulloch, Va’vra converted the DIRC’s simple pinhole camera into a camera with sophisticated, solid fused-silica optics, while shrinking it to 1/25th its former size and enabling it to collect data 10 times faster.

    The resulting Focused Detection of Internally Reflected Cherenkov light (FDIRC) detector represents an important technical advance in high-energy physics detector science.

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    Jerry Va’vra, SLAC detector physicist, buffs the large block of fused silica that will focus photons of Cherenkov light toward photon detectors that will capture them in the prototype of the Focused Detection of Internally Reflected Cherenkov light detector being built in Building 121. The FDIRC will enable high-energy physicists to decipher the types of particles that generated the Cherenkov light in the first place.

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    Jerry Va’vra, SLAC detector physicist, shows a block of fused silica that will direct captured photons of Cherenkov light toward the focusing block in the prototype of the Focused Detection of Internally Reflected Cherenkov light detector being built in Building 121.

    See the full article here.

    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 5:35 pm on February 2, 2012 Permalink | Reply
    Tags: , , , , , SLAC BaBar   

    From SLAC Today: “BaBar Extends the Search for New Matter-Antimatter Asymmetries” 

    February 2, 2012
    Lori Ann White

    “The BaBar collaboration’s detailed studies of the subtle ways in which matter behaves differently from antimatter are hailed as one of the success stories of experimental high-energy physics. After all, BaBar data and measurements have confirmed a nearly 40-year-old theory that explained the asymmetry between matter and antimatter, and helped convince the Nobel Prize committee to award the 2008 Nobel Prize in Physics to Makoto Kobayashi and Toshihide Maskawa, the two Japanese developers of that theory.

    But BaBar’s SLAC-based search for matter-antimatter asymmetries did not end there. Perhaps Kobayashi’s and Maskawa’s theory, which is now part of the Standard Model of particles and interactions, is not the whole story.

    ‘We know our current picture of particle physics, the Standard Model, cannot be complete, as it vastly underestimates the universe’s matter-antimatter asymmetry,’ said Aaron Roodman of SLAC and Stanford’s Kavli Institute for Particle Astrophysics and Cosmology. ‘Some new source of asymmetry in particle interactions or decays must exist.’ ”

    See the rest of the article here.

    So, just what is BaBar?

    “For each particle of matter there exists an equivalent particle with opposite quantum characteristics, called an anti-particle. Particle and anti-particle pairs can be created by large accumulations of energy and, conversely, when a particle meets an anti-particle they annihilate with intense blasts of energy. At the time of the big-bang, the large accumulation of energy must have created an equal amount of particles and anti-particles. But in everyday life we do not encounter anti-particles. The question, therefore, is “What has happened to the anti-particles?”

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    BaBar Detector

    BABAR is a High Energy Physics experiment located at SLAC National Accelerator Laboratory, near Stanford University, in California.

    The goal of the experiment is to study the violation of charge and parity (CP) symmetry in the decays of B mesons. This violation manifests itself as different behaviour between particles and anti-particles and is the first step to explain the absence of anti-particles in everyday life.

    To study CP violation the BABAR experiment exploits the 9.1 GeV electron beam and the 3 GeV positron beam of the PEP-II accelerator. The two beams collide in the center of the experiment, producing Υ(4S) mesons which decay into equal numbers of B and anti-B mesons.

    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. i1

     
  • richardmitnick 2:26 pm on December 5, 2011 Permalink | Reply
    Tags: , , , , , , SLAC BaBar   

    From SLAC Today: “BaBar Studies Matter-Antimatter Asymmetry in Tau Lepton Decays” 

    “December 5, 2011
    Lori Ann White

    Since 1999, physicists from the BaBar experiment at SLAC National Accelerator Laboratory have been studying a fundamental question about the universe – why does it contain so much more matter than antimatter? The laws of physics are remarkably symmetric, affecting both matter and antimatter almost identically.

    But the very existence of the matter around us demonstrates that these laws show a slight, but clear, bias toward matter. The BaBar team should know. They’ve used the data they collected for nine years to study a particular example of this cosmic favoritism – what’s called a matter-antimatter asymmetry in the decays of bottom and anti-bottom quarks.

    BaBar physicists are continuing to exploit the data in various new ways. This includes studies of matter-antimatter asymmetries in other particles than bottom quarks, where the potential for major discovery is still untapped.”

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    The PEP rings and the BaBar Detector

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    See the full article here.

    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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