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  • richardmitnick 11:26 am on November 8, 2017 Permalink | Reply
    Tags: , , KEK Belle II, , , , ,   

    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: , , , , , , KEK Belle II, , , , 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 4:55 pm on May 19, 2017 Permalink | Reply
    Tags: , , Belle II rolls in, , , KEK Belle II, , ,   

    From CERN Courier: “Belle II rolls in” 

    CERN Courier

    May 19, 2017

    1
    The Belle II detector in place

    On 11 April, the Belle II detector at the KEK laboratory in Japan was successfully “rolled-in” to the collision point of the upgraded SuperKEKB accelerator, marking an important milestone for the international B-physics community. The Belle II experiment is an international collaboration hosted by KEK in Tsukuba, Japan, with related physics goals to those of the LHCb experiment at CERN but in the pristine environment of electron–positron collisions. It will analyse copious quantities of B mesons to study CP violation and signs of physics beyond the Standard Model (CERN Courier September 2016 p32).

    “Roll-in” involves moving the entire 8 m-tall, 1400 tonne Belle II detector system from its assembly area to the beam-collision point 13 m away. The detector is now integrated with SuperKEKB and all its seven subdetectors, except for the innermost vertex detector, are in place. The next step is to install the complex focusing magnets around the Belle II interaction point. SuperKEKB achieved its first turns in February, with operation of the main rings scheduled for early spring and phase-II “physics” operation by the end of 2018.

    Compared to the previous Belle experiment, and thanks to major upgrades made to the former KEKB collider, Belle II will allow much larger data samples to be collected with much improved precision. “After six years of gruelling work with many unexpected twists and turns, it was a moving and gratifying experience for everyone on the team to watch the Belle II detector move to the interaction point,” says Belle II spokesperson Tom Browder. “Flavour physics is now the focus of much attention and interest in the community and Belle II will play a critical role in the years to come.”

    See the full article here .

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    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

     
  • richardmitnick 12:28 pm on April 1, 2016 Permalink | Reply
    Tags: , , , KEK Belle II, , ,   

    From Symmetry: “Belle II and the matter of antimatter” 

    Symmetry Mag
    Symmetry

    04/01/16
    Matthew R. Francis

    DESY Belle II detector
    DESY Belle II detector

    Go inside the new detector looking for why we’re here.

    We live in a world full of matter: stars made of matter, planets made of matter, pizza made of matter. But why is there pizza made of matter rather than pizza made of antimatter or, indeed, no pizza at all?

    In the first split-second after the big bang, the universe made a smidgen more matter than antimatter. Instead of matter and antimatter annihilating one another and leaving an empty, cold universe, we ended up with a surplus of stuff. Now scientists need the most sensitive detectors and mountains of experimental data to understand where that imbalance comes from.

    Belle II is one of those detectors that will look for differences between matter and antimatter to explain why we’re here at all. Currently under construction, the 7.5-meter-long detector will be installed in the newly recommissioned SuperKEKB particle accelerator located in Tsukuba, Japan.

    SuperKEKB accelerator Japan
    SuperKEKB accelerator Japan

    SuperKEKB runs beams of electrons and positrons (the antimatter version of electrons) into each other at close to the speed of light, and Belle II—once it is fully operational in 2018—will analyze the detritus of the collisions.

    “All the experimental results to this point have been consistent with the so-called Standard Model of particle physics,” says Tom Browder, a physicist at the University of Hawaii and one of the spokespeople for the project.

    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.
    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.

    But while the Standard Model allows for some asymmetry, it doesn’t explain the matter-antimatter imbalance that exists. We need something more.

    Belle II will look for the signatures of new physics in the rare decays of bottom quarks, charm quarks and tau leptons. (Bottom quarks are also known as beauty quarks, which is the “B” in SuperKEKB; the name “Belle” itself refers to “beauty”). Bottom and charm quarks are massive compared with the up and down quarks that make up ordinary matter, while tau leptons are the much heavier cousins of electrons. All three particles are unstable, decaying into a variety of lower-mass particles. If Belle II researchers spot a difference in the decays of these particles and their antimatter counterparts, it could explain why we ended up in a cosmos full of matter.

    Finding the beauty is a beast

    When electrons and positrons collide at low energy, they annihilate and convert all of their mass into gamma rays. At very high speed, however, the extra energy produces pairs of matter and antimatter particles, all of which are more massive than the original electrons. SuperKEKB smashes electrons and positrons together with the right energy to make B-mesons, particles made of a bottom quark and an antimatter quark of another type, along with anti-B-mesons, made of a bottom anti-quark and a matter quark.

    These mesons change into other particles in complex ways as the bottom quarks and antiquarks decay. Belle II’s detectors will try to find decays that either aren’t allowed by the Standard Model or happen more or less often than expected. Any such deviations could be signs of new physics. The detector can also help physicists better understand particles made of four or five quarks (tetraquarks and pentaquarks) or stuck-together “molecules” of quarks.

    “The cleaner environment at Belle II might make it easier to study some of those states, and to try to understand what the internal quark structure is,” says James Fast of the Department of Energy’s Pacific Northwest National Laboratory, lead lab for the US contributions to the Belle II detector upgrade.

    SuperKEKB collides electrons and positrons, which aren’t made of anything smaller. This results in a clean collision. And because the energy going into each collision at SuperKEKB is well known, Belle II can study decays with invisible particles such as neutrinos by looking for the missing energy they carry away.

    “The cleanliness of data at SuperKEKB enables the majority of B[-meson] events to be recorded,” says Kay Kinoshita of the University of Cincinnati, who works on the software Belle II will use to analyze collisions.

    But Belle II isn’t the only detector searching for these rare bottom quark decays. An experiment at the LHC, LHCb, is also on the hunt.

    CERN LHC LHCb
    CERN LHC LHCb

    The LHC produces a wider variety of particles containing bottom quarks. That includes a type that decays into two muons, “which is a ‘golden’ mode for effects from supersymmetry and theories with multiple Higgs bosons,” says Harry Cliff, a physicist at the University of Cambridge who works on LHCb.

    Race to the bottom

    Belle II is the aptly named successor to the Belle experiment and is designed to handle as much as 50 times the number of collisions in the previous design. It’s a monumental effort involving hundreds of physicists and engineers from 23 nations in Asia, Europe and North America.

    “The amount of data that Belle II will collect can be comparable to data management challenges that are faced by the big LHC experiments [like CMS and ATLAS],” says Fast.

    CERN CMS Detector
    CERN CMS Detector

    CERN/ATLAS
    CERN/ATLAS

    Universities don’t have the resources to operate the computers needed to manage all the data coming from Belle II, so a national lab like PNNL is an ideal host. Similar data centers for Belle II will operate in Japan and Europe.

    At present, the SuperKEKB accelerator is successfully storing both electrons and positrons to prepare for the tests that will lead to new experiments. The Belle II assembly will be in place next year, followed by a commissioning process to make sure everything is working properly. In 2018, the full experiment will be operational and producing data to find exotic B-meson behavior.

    It may feel ironic to take years to recreate what the universe did in a split second, but such is the nature of particle physics. The process of smashing electrons and positrons together isn’t identical to the process that created the early cosmos either, but if there’s any new physics hiding in the decays of bottom quarks, this is the type of experiment that could find it. Which is, after all, the beauty of science.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
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