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  • richardmitnick 8:21 am on July 29, 2015 Permalink | Reply
    Tags: , , CERN LHCb, , , , Pentaquarks   

    From NOVA: “What the Heck is a Pentaquark?” 

    PBS NOVA

    NOVA

    28 Jul 2015
    FNAL Don Lincoln
    Don Lincoln

    What do you get when you combine four quarks and an antiquark?

    If you think this sounds like the opening of a particle physicists’ riddle, you aren’t too far off. Hypothetically, this particular quark combo makes a “pentaquark.” Despite decades of searching, physicists haven’t been able to actually find a pentaquark. Now, though, there’s a hint that two pentaquarks have unexpectedly come out of hiding.

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    Illustration of a possible layout of the quarks in a pentaquark particle such as those discovered at LHCb. © CERN

    If the new result holds up—a big if—the unexpected discovery would add a new species of particle to the standard model’s menagerie. But the measurements, recently announced by the team collaborating on the LHCb experiment, are truly perplexing.

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    LHCb on the LHC at CERN

    While the results were submitted for publication a couple of days ago, the first discussion in a large public conference occurred on July 23 at the 2015 meeting of the high energy physics division of the European Physical Society, where I had the opportunity to hear Sheldon Stone, who led the analysis, talk about the result. It’s certainly a topic of both excited and skeptical discussion here at the conference.

    Pentaquarks were first predicted in 1964 by Murray Gell-man and George Zweig in the separate and competing papers in which they first hypothesized the existence of quarks. (Gell-man’s name “quark” has stood the test of time, while Zweig independently proposed the now-defunct “aces.”) Physicists have looked for pentaquarks for a long time, unsuccessfully. We don’t know why there has been no evidence for their existence for so long. Maybe they don’t exist. Or maybe they do and the LHCb experiment has finally found them.

    Quarks are the building blocks of protons and neutrons and, as far as we know, they are the smallest basic units of matter. Quarks combine with other quarks according to the rules of quantum chromodynamics (QCD), which is the theory describing the behavior of the strong nuclear force, which is the strongest of the known subatomic forces. Pair a quark with an antiquark, and you’ve got a particle called a meson; three quarks make a baryon, like a proton or neutron. The new pentaquark—if it really is a pentaquark—seems to be made up of two up quarks, a down quark, and a charm quark/antiquark pair.

    The announcement is the latest chapter in a somewhat dubious story of now-you-see-now-you-don’t discovery. In 2002, scientists in Japan announced the discovery of a particle with a mass about 1.5 times that of a proton. They called it the Θ+, and argued that it was a kind of pentaquark. This announcement triggered a flurry of searches by other groups of experimenters, with some groups confirming the Θ+ and finding other particles that were claimed to be different pentaquark candidates, while other researchers found no evidence for any new particles at all. The excitement continued for three years until 2005, when the community decided that the original announcement was wrong. The death knell of the Θ+ sounded when a group of scientists at the Thomas Jefferson National Accelerator Facility (TJNAF) in Newport News, Virginia, repeated the initial Japanese measurement with far more data. The TJNAF scientists saw no evidence for the existence of the Θ+, and the community consigned it to the dustbin of history as one of many particle “discoveries” that ultimately didn’t pan out.

    The particles recently announced by the LHCb experiment aren’t the Θ+. Instead, the new particles have a mass of about 4.5 times that of the proton. The LHCb team wasn’t actually searching for pentaquarks when they made their measurements. Instead, they were studying how a particle called the Λb baryon decays. To their surprise, they found that a fraction of the time, some of the “daughter” particles left behind by the decay seemed to be coming from an unknown parent particle. So what the heck was it?

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    The LCHb team found the potential pentaquarks while investigating how a Λb baryon decays into a J/ψ meson and a Λ* baryon, which in turn decays into a K- meson and a proton (p+). In such a complicated decay mode, it is customary to look at the three daughter particles two at a time and calculate what the mass of the parent particle could have made them. In the case of the K- meson and a proton, you’d expect to see that they preferentially came from a particle with a mass of a Λ* baryon. Since the J/ψ and the proton weren’t thought to come from the decay of a single particle, you’d expect to see no particular mass looking special—but, as seen here, the researchers saw that a fraction of the time, these two particles seemed to come from a parent with a specific mass. Could pentaquarks be the culprit? Image adapted by Don Lincoln.

    The LHCb team was unable to reconcile their measurements with any of the known or predicted particles of the Standard Model.

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    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.

    They seemed to need something new. After testing out lots of hypotheses, they considered the discredited pentaquarks. (Remember that pentaquarks are a prediction of the theory of QCD, they’ve just never been seen before.) One pentaquark wasn’t enough to fit their data, but two did the trick. When they included two new pentaquark particles in their calculations, the data and theory agreed.

    The two new particles have an unusual amount of quantum mechanical spin, specifically 3/2 and 5/2. (Protons, neutrons and electrons are all spin ½.) Like all particles that are bound by the strong nuclear force and decay under its rules, they live for a very short time, specifically about 10-23 seconds.

    Given the checkered history of previous pentaquark searches, physicists are naturally skeptical. So it is worth dissecting the claim. The first question is whether scientists are confident that they’ve discovered some kind of new particle. Here, the claim is on firmer ground: the two detections have significance of nine and 12 standard deviations respectively. (The usual standard in particle physics to claim the discovery of a phenomenon is five standard deviations, and larger numbers mean more certainty. Nine and 12 are very strong numbers.)

    It’s less certain whether the new particles are really pentaquarks. There are good reasons for skepticism: For one thing, the makeup of the new pentaquarks—two ups, a down, and a charm quark/antiquark pair—seems improbable. It should be easier to make a pentaquark consisting of only up and down quarks, which are lighter than charm quarks, and such a particle has never been discovered. Discovering a charm pentaquark first feels like going fishing and pulling up two sharks and no trout. A second possibility is that the new discovery is actually a sort of “molecule”: a particle called a J/ψ attached to a proton, roughly similar to how a deuteron is a proton and neutron bound together. Both have the same quark content, but only “five things in a bag” qualifies as a “real” pentaquark.

    When I caught up with Sheldon Stone during the coffee break after his talk at the conference, he speculated that the higher mass of the charm quarks could make the resulting pentaquark more stable or perhaps somehow makes this sort of pentaquark more likely to form. He cautioned, however, that this was speculation on his part and more work would be required to substantiate these ideas.

    Theoretical physicists are likewise skeptical. Frank Wilczek, professor of physics at MIT and winner of the Nobel Prize in physics for his contributions to the development of the theory of QCD was excited about the possibility of the existence of the pentaquark, but cautious about the measurement.

    So what will it take for the community to embrace this exciting development? Well, as Carl Sagan is famous for noting, extraordinary claims require extraordinary evidence. It is also true that independent confirmation is key. Accordingly, other LHC experiments will try to repeat the analysis approach reported by the LHCb collaboration in order to see if their measurement can be replicated. In addition, theorists will try to see if they can find a mechanism within QCD that will explain why pentaquarks containing charm quarks are more likely to form than ones with lighter quarks.

    Now, taking a more personal perspective, what do I think? First, Sheldon Stone made a persuasive and thorough case at his talk. I think the LHCb experiment is a world class collaboration, with some of the finest minds on the planet and ample experience in the subject matter. Further, they are well aware of the history of the pentaquark and would not lightly propose this hypothesis without adequate care. However, I am very cautious of claims of this nature, especially without confirmation from other experiments. I think the only sensible approach is to view the claim charitably, but critically. Taking a phrase from President Ronald Reagan, I “trust, but verify.” I think the next few months will be very interesting.

    See the full article here.

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    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
  • richardmitnick 11:58 am on July 14, 2015 Permalink | Reply
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    From CERN: “CERN’s LHCb experiment reports observation of exotic pentaquark particles” 

    CERN New Masthead

    14 Jul 2015
    No Writer Credit

    Today, the LHCb experiment at CERN’s Large Hadron Collider has reported the discovery of a class of particles known as pentaquarks. The collaboration has submitted a paper reporting these findings to the journal Physical Review Letters.

    “The pentaquark is not just any new particle,” said LHCb spokesperson Guy Wilkinson. “It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over fifty years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we’re all made, is constituted.”

    Our understanding of the structure of matter was revolutionized in 1964 when American physicist, Murray Gell-Mann, proposed that a category of particles known as baryons, which includes protons and neutrons, are comprised of three fractionally charged objects called quarks, and that another category, mesons, are formed of quark-antiquark pairs. Gell-Mann was awarded the Nobel Prize in physics for this work in 1969. This quark model also allows the existence of other quark composite states, such as pentaquarks composed of four quarks and an antiquark. Until now, however, no conclusive evidence for pentaquarks had been seen.

    LHCb researchers looked for pentaquark states by examining the decay of a baryon known as Λb (Lambda b) into three other particles, a J/ψ- (J-psi), a proton and a charged kaon. Studying the spectrum of masses of the J/ψ and the proton revealed that intermediate states were sometimes involved in their production. These have been named Pc(4450)+ and Pc(4380)+, the former being clearly visible as a peak in the data, with the latter being required to describe the data fully.

    “Benefitting from the large data set provided by the LHC, and the excellent precision of our detector, we have examined all possibilities for these signals, and conclude that they can only be explained by pentaquark states”, says LHCb physicist Tomasz Skwarnicki of Syracuse University.

    “More precisely the states must be formed of two up quarks, one down quark, one charm quark and one anti-charm quark.”

    Earlier experiments that have searched for pentaquarks have proved inconclusive. Where the LHCb experiment differs is that it has been able to look for pentaquarks from many perspectives, with all pointing to the same conclusion. It’s as if the previous searches were looking for silhouettes in the dark, whereas LHCb conducted the search with the lights on, and from all angles. The next step in the analysis will be to study how the quarks are bound together within the pentaquarks.

    “The quarks could be tightly bound,” said LHCb physicist Liming Zhang of Tsinghua University, “or they could be loosely bound in a sort of meson-baryon molecule, in which the meson and baryon feel a residual strong force similar to the one binding protons and neutrons to form nuclei.”

    More studies will be needed to distinguish between these possibilities, and to see what else pentaquarks can teach us. The new data that LHCb will collect in LHC run 2 will allow progress to be made on these questions.

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    2
    Illustration of the possible layout of the quarks in a pentaquark particle such as those discovered at LHCb. The five quarks might be tightly bonded (left). They might also be assembled into a meson (one quark and one antiquark) and a baryon (three quarks), weakly bound together. © CERN

    See the full article here.

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  • richardmitnick 2:53 pm on May 13, 2015 Permalink | Reply
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    From FNAL: “Two Large Hadron Collider experiments first to observe rare subatomic process” 

    FNAL Home

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

    May 13, 2015
    MEDIA CONTACTS
    Andre Salles, Fermilab Office of Communication, 630-840-3351, media@fnal.gov
    Sarah Charley, US LHC/CERN, +41 22 767 2118, sarah.charley@cern.ch

    SCIENCE CONTACTS
    Joel Butler, CMS experiment, Fermilab, 630-651-4619, butler@fnal.gov
    Sarah Scalese, LHCb experiment, Syracuse University, 315-443-8085, sescales@syr.edu

    1
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    Event displays from the CMS (above) and LHCb (below) experiments on the Large Hadron Collider show examples of collisions that produced candidates for the rare decay of the Bs particle, predicted and observed to occur only about four times out of a billion. Images: CMS/LHCb collaborations

    Two experiments at the Large Hadron Collider [LHC] at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, have combined their results and observed a previously unseen subatomic process.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    As published in the journal Nature this week, a joint analysis by the CMS and LHCb collaborations has established a new and extremely rare decay of the Bs particle (a heavy composite particle consisting of a bottom antiquark and a strange quark) into two muons. Theorists had predicted that this decay would only occur about four times out of a billion, and that is roughly what the two experiments observed.

    CERN CMS Detector
    CMS

    CERN LHCb New II
    LHCb

    “It’s amazing that this theoretical prediction is so accurate and even more amazing that we can actually observe it at all,” said Syracuse University Professor Sheldon Stone, a member of the LHCb collaboration. “This is a great triumph for the LHC and both experiments.”

    LHCb and CMS both study the properties of particles to search for cracks in the Standard Model, our best description so far of the behavior of all directly observable matter in the universe.

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    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    The Standard Model is known to be incomplete since it does not address issues such as the presence of dark matter or the abundance of matter over antimatter in our universe. Any deviations from this model could be evidence of new physics at play, such as new particles or forces that could provide answers to these mysteries.

    “Many theories that propose to extend the Standard Model also predict an increase in this Bs decay rate,” said Fermilab’s Joel Butler of the CMS experiment. “This new result allows us to discount or severely limit the parameters of most of these theories. Any viable theory must predict a change small enough to be accommodated by the remaining uncertainty.”

    Researchers at the LHC are particularly interested in particles containing bottom quarks because they are easy to detect, abundantly produced and have a relatively long lifespan, according to Stone.

    “We also know that Bs mesons oscillate between their matter and their antimatter counterparts, a process first discovered at Fermilab in 2006,” Stone said. “Studying the properties of B mesons will help us understand the imbalance of matter and antimatter in the universe.”

    That imbalance is a mystery scientists are working to unravel. The big bang that created the universe should have resulted in equal amounts of matter and antimatter, annihilating each other on contact. But matter prevails, and scientists have not yet discovered the mechanism that made that possible.

    “The LHC will soon begin a new run at higher energy and intensity,” Butler said. “The precision with which this decay is measured will improve, further limiting the viable Standard Model extensions. And of course, we always hope to see the new physics directly in the form of new particles or forces.”

    This discovery grew from analysis of data taken in 2011 and 2012 by both experiments. Scientists also saw some evidence for this same process for the Bd particle, a similar particle consisting of a bottom antiquark and a down quark. However, this process is much more rare and predicted to occur only once out of every 10 billion decays. More data will be needed to conclusively establish its decay to two muons.

    The U.S. Department of Energy Office of Science provides funding for the U.S. contributions to the CMS experiment. The National Science Foundation provides funding for the U.S. contributions to the CMS and LHCb experiments. Together, the CMS and LHCb collaborations include more than 4,500 scientists from more than 250 institutions in 44 countries.

    The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

    The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2015, its budget is $7.3 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives about 48,000 competitive proposals for funding, and makes about 11,000 new funding awards. NSF also awards about $626 million in professional and service contracts yearly.

    CERN, the European Organization for Nuclear Research, is the world’s leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Union, JINR and UNESCO have Observer Status.

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    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 5:56 pm on November 23, 2014 Permalink | Reply
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    From LHCb at CERN: “The proton beam knocks at the LHC door” 

    CERN New Masthead

    23 November 2014
    No Writer Credit

    The LHCb collaboration took proton interaction data this weekend

    team
    LHCb is an experiment set up to explore what happened after the Big Bang that allowed matter to survive and build the Universe we inhabit today.

    The proton beam knocked at the LHC’s very solid door this weekend and found it still closed, but nonetheless managed to provide the LHCb collaboration with very interesting data. The CERN accelerator system (see video) is now fully operational, except for the LHC collider itself. This past weekend, CERN accelerator system operators tested the two transfer lines between the SPS and LHC. One of these lines ends with a so-called beam stopper known as the “TED”, located at the end of the line about 300m from the LHCb detector. The TED is currently closed, and so absorbed the proton beam before it could enter the LHC. However many muons were produced during the absorption process, and these muons passed through the TED and traversed the LHCb detector.

    This “beam dump” experiment therefore created an excellent opportunity for LHCb physicists and engineers to commission the LHCb detector and data acquisition system. The collected data are also useful for detector studies and alignment purposes (i.e. determining the relative geometrical locations of the different sub-detectors with respect to each other).

    gr
    The image shows the shift leader, run coordinator, spokesperson and sub-detector experts in front of the LHCb data acquisition computer screens.

    LHCb took its last collision data on 14th February 2013. The two year Long Shutdown 1 (LS1) period that followed has been used for an extensive program of consolidation and maintenance (see 24 January 2014 “underground” news). Collisions are expected to resume again in Spring 2015.

    CERN LHC Map
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    LHC at CERN

    See the full article, with video, here.

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  • richardmitnick 3:00 pm on November 22, 2014 Permalink | Reply
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    From Triumf: “LHCb Experiment Confirms TRIUMF Prediction” 

    On Wednesday, November 19th, the LHCb collaboration at CERN’s Large Hadron Collider (LHC) announced the discovery of two new particles in the baryon family. The particles, known as the Xi_b’- and Xi_b*-, were predicted to exist by the quark model but had never been seen before.

    CERN LHCb New
    LHCb at CERN

    Randy Lewis, York University, and Richard Woloshyn (photographed), TRIUMF, submitted a paper together in 2009, “Bottom baryons from a dynamical lattice QCD simulation,” in which the masses of Xi_b’- and Xi_b* were predicted. This paper, among the eight theoretical papers cited in the LHCb collaboration report submitted to the Physical Review Letters, offered the LHCb researchers a light in the path of discovery.

    rw
    Richard Woloshyn

    “Theoretical and experimental physics complement each other in an important way,” said Petr Navratil, Head of Theory Department at TRIUMF. “Richard’s work illustrates how theoretical predictions motivate experimental efforts. Experimental results then provide feedback to improve the theoretical understanding.”

    The new particles are baryons made from three quarks bound together by the strong force. The types of quarks are different, though: the new Xib particles both contain one beauty (b), one strange (s), and one down (d) quark. Thanks to the heavyweight b quarks, the baryons are more than six times as massive as the proton. But the particles are more than just the sum of their parts: their mass also depends on how they are configured. Each of the quarks has an attribute called “spin“. In the Xi_b’- state, the spins of the two lighter quarks point in opposite directions, whereas in the Xi_b*- state they are aligned. This difference makes the Xi_b*- a little heavier.

    “Nature was kind and gave us two particles for the price of one,” said
    Matthew Charles of the CNRS’s LPNHE laboratory at Paris VI University.

    “The Xi_b’- is very close in mass to the sum of its decay products: if it had been just a little lighter, we wouldn’t have seen it at all using the decay signature that we were looking for.”

    “This is a very exciting result. Thanks to LHCb’s excellent hadron identification, which is unique among the LHC experiments, we were able to separate a very clean and strong signal from the background,” said Steven Blusk from Syracuse University in New York. “It demonstrates once again the sensitivity and how precise the LHCb detector is.”

    “I am happy that LHCb cites our work and that it appears on the broader stage, ” said Richard Woloshyn, “It shows the work we do here at TRIUMF and in Canada is important.”

    As well as the masses of these particles, the LHCb team studied their relative production rates, their widths – a measure of how unstable they are – and other details of their decays. The results match up with predictions based on the theory of Quantum Chromodynamics (QCD). QCD is part of the Standard Model of particle physics, the theory that describes the fundamental particles of matter, how they interact and the forces between them.

    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.

    “Our approach was based directly on QCD. These results give us confidence and show that the theory is adequate to deal with any measurement and to predict the outcomes of experiments,” said Richard.

    “This success is a reminder of TRIUMF’s leadership role in theoretical physics. Richard has been using the computational method called lattice QCD to make important contributions for many years, and I am one of several people who learned lattice QCD by spending time at TRIUMF with Richard,” said Randy Lewis.

    Richard admits that when he first saw the InterActions news release he did not expect it to be related to one of his theoretical ‘discoveries’ and set it aside to read later. It wasn’t until he saw the CBC headline, “New subatomic particles predicted by Canadians found at CERN” that he knew of his part in the discovery.

    See the full article here..

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    Triumf Campus
    Triumf Campus

    World Class Science at Triumf Lab, British Columbia, Canada
    Canada’s national laboratory for particle and nuclear physics
    Member Universities:
    University of Alberta, University of British Columbia, Carleton University, University of Guelph, University of Manitoba, Université de Montréal, Simon Fraser University,
    Queen’s University, University of Toronto, University of Victoria, York University. Not too shabby, eh?

    Associate Members:
    University of Calgary, McMaster University, University of Northern British Columbia, University of Regina, Saint Mary’s University, University of Winnipeg, How bad is that !!

     
  • richardmitnick 9:42 am on November 19, 2014 Permalink | Reply
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    From LHCb at CERN: “LHCb experiment observes two new baryon particles never seen before” 

    CERN New Masthead

    19 Nov 2014
    No Writer Credit

    graph

    Geneva 19 November 2014. Today the collaboration for the LHCb experiment at CERN’s Large Hadron Collider announced the discovery of two new particles in the baryon family. The particles, known as the Xi_b’- and Xi_b*-, were predicted to exist by the quark model but had never been seen before. A related particle, the Xi_b*0, was found by the CMS experiment at CERN in 2012. The LHCb collaboration submitted a paper reporting the finding to Physical Review Letters.

    CERN LHCb New
    LHCb at CERN

    CERN LHC Map
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    CERN LHC particles
    LHC at CERN

    Like the well-known protons that the LHC accelerates, the new particles are baryons made from three quarks bound together by the strong force. The types of quarks are different, though: the new X_ib particles both contain one beauty (b), one strange (s), and one down (d) quark. Thanks to the heavyweight b quarks, they are more than six times as massive as the proton. But the particles are more than just the sum of their parts: their mass also depends on how they are configured. Each of the quarks has an attribute called “spin“. In the Xi_b’- state, the spins of the two lighter quarks point in opposite directions, whereas in the Xi_b*- state they are aligned. This difference makes the Xi_b*- a little heavier.

    “Nature was kind and gave us two particles for the price of one,” said Matthew Charles of the CNRS’s LPNHE laboratory at Paris VI University. “The Xi_b’- is very close in mass to the sum of its decay products: if it had been just a little lighter, we wouldn’t have seen it at all using the decay signature that we were looking for.”

    “This is a very exciting result. Thanks to LHCb’s excellent hadron identification, which is unique among the LHC experiments, we were able to separate a very clean and strong signal from the background,” said Steven Blusk from Syracuse University in New York. “It demonstrates once again the sensitivity and how precise the LHCb detector is.”

    As well as the masses of these particles, the research team studied their relative production rates, their widths – a measure of how unstable they are – and other details of their decays. The results match up with predictions based on the theory of Quantum Chromodynamics (QCD).

    QCD is part of the Standard Model of particle physics, the theory that describes the fundamental particles of matter, how they interact and the forces between them. Testing QCD at high precision is a key to refine our understanding of quark dynamics, models of which are tremendously difficult to calculate.

    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.

    “If we want to find new physics beyond the Standard Model, we need first to have a sharp picture,” said LHCb’s physics coordinator Patrick Koppenburg from Nikhef Institute in Amsterdam. “Such high precision studies will help us to differentiate between Standard Model effects and anything new or unexpected in the future.”

    The measurements were made with the data taken at the LHC during 2011-2012. The LHC is currently being prepared – after its first long shutdown – to operate at higher energies and with more intense beams. It is scheduled to restart by spring 2015.

    Further information

    Caption diagram : The mass difference spectrum: the LHCb result shows strong evidence of the existence of two new particles the Xi_b’- (first peak) and Xi_b*- (second peak), with the very high-level confidence of 10 sigma. The black points are the signal sample and the hatched red histogram is a control sample. The blue curve represents a model including the two new particles, fitted to the data. Delta_m is the difference between the mass of the Xi_b0 pi- pair and the sum of the individual masses of the Xi_b0 and pi-.. INSET: Detail of the Xi_b’- region plotted with a finer binning.

    Link to the paper on Arxiv: http://arxiv.org/abs/1411.4849
    More about the result on LHCb’s collaboration website: http://lhcb-public.web.cern.ch/lhcb-public/Welcome.html#StrBeaBa
    Observation of a new Xi_b*0 beauty particle, on CMS’ collaboration website: http://cms.web.cern.ch/news/observation-new-xib0-beauty-particle
    Footnote(s)

    1. CERN, the European Organization for Nuclear Research, is the world’s leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer Status.

    See the full article here.
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  • richardmitnick 5:20 pm on October 28, 2014 Permalink | Reply
    Tags: , B meson, CERN LHCb, , , , , Syracuse University   

    From Syracuse University: “Syracuse Physicists Closer to Understanding Balance of Matter, Antimatter” 

    Syracuse University

    Syracuse University

    Physicists in the College of Arts and Sciences have made important discoveries regarding Bs meson particles—something that may explain why the universe contains more matter than antimatter.

    ss
    Sheldon Stone

    Distinguished Professor Sheldon Stone and his colleagues recently announced their findings at a workshop at CERN in Geneva, Switzerland. Titled Implications of LHCb Measurements and Their Future Prospects, the workshop enabled him and other members of the Large Hadron Collider beauty (LHCb) Collaboration to share recent data results.

    CERN LHCb New
    CERN LHCb

    The LHCb Collaboration is a multinational experiment that seeks to explore what happened after the Big Bang, causing matter to survive and flourish in the Universe. LHCb is an international experiment, based at CERN, involving more than 800 scientists and engineers from all over the world. At CERN, Stone heads up a team of 15 physicists from Syracuse.

    “Many international experiments are interested in the Bs meson because it oscillates between a matter particle and an antimatter particle,” says Stone, who heads up Syracuse’s High-Energy Physics Group. “Understanding its properties may shed light on charge-parity [CP] violation, which refers to the balance of matter and antimatter in the universe and is one of the biggest challenges of particle physics.”

    Scientists believe that, 14 billion years ago, energy coalesced to form equal quantities of matter and antimatter. As the universe cooled and expanded, its composition changed. Antimatter all but disappeared after the Big Bang (approximately 3.8 billion years ago), leaving behind matter to create everything from stars and galaxies to life on Earth.

    “Something must have happened to cause extra CP violation and, thus, form the universe as we know it,” Stone says.

    He thinks part of the answer lies in the Bs meson, which contains an antiquark and a strange quark and is bound together by a strong interaction. (A quark is a hard, point-like object found inside a proton and neutron that forms the nucleus of an atom.)

    Enter CERN, a European research organization that operates the world’s largest particle physics laboratory.

    In Geneva, Stone and his research team—which includes Liming Zhang, a former Syracuse research associate who is now a professor at Tsinghua University in Beijing, China—have studied two landmark experiments that took place at Fermilab, a high-energy physics laboratory near Chicago, in 2009.

    lhc
    The Large Hadron Collider at CERN

    The experiments involved the Collider Detector at Fermilab (CDF) and the DZero (D0), four-story detectors that were part of Fermilab’s now-defunct Tevatron, then one of the world’s highest-energy particle accelerators.

    “Results from D0 and CDF showed that the matter-antimatter oscillations of the Bs meson deviated from the standard model of physics, but the uncertainties of their results were too high to make any solid conclusions,” Stone says.

    He and Zhang had no choice but to devise a technique allowing for more precise measurements of Bs mesons. Their new result shows that the difference in oscillations between the Bs and anti-Bs meson is just as the standard model has predicted.

    Stone says the new measurement dramatically restricts the realms where new physics could be hiding, forcing physicists to expand their searches into other areas. “Everyone knows there is new physics. We just need to perform more sensitive analyses to sniff it out,” he adds.

    See the full article here.

    Syracuse University was officially chartered in 1870 as a private, coeducational institution offering programs in the physical sciences and modern languages. The university is located in the heart of Central New York, is within easy driving distance of Toronto, Boston, Montreal, and New York City. SU offers a rich mix of academic programs, alumni activities, and immersion opportunities in numerous centers in the U.S. and around the globe, including major hubs in New York City, Washington, D.C., and Los Angeles. The total student population at Syracuse University represents all 50 U.S. states and 123 countries.

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  • richardmitnick 7:38 pm on October 14, 2014 Permalink | Reply
    Tags: , , CERN LHCb, , , , ,   

    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 1:29 pm on October 9, 2014 Permalink | Reply
    Tags: , , CERN LHCb, , , , U Warwick   

    From Warwick: “Discovery of new subatomic particle sheds light on fundamental force of nature “ 

    University of Warwick

    University of Warwick

    9 October 2014
    No Writer Credit

    The discovery of a new particle will “transform our understanding” of the fundamental force of nature that binds the nuclei of atoms, researchers argue.

    Led by scientists from the University of Warwick, the discovery of the new particle will help provide greater understanding of the strong interaction, the fundamental force of nature found within the protons of an atom’s nucleus.

    what
    Credit: Science and Technology Facilities Council

    Named Ds3*(2860)ˉ, the particle, a new type of meson,[1] was discovered by analysing data collected with the LHCb detector at CERN’s Large Hadron Collider (LHC)[2]. The LHCb experiment, which is run by a large international collaboration, is designed to study the properties of particles containing beauty and charm quarks and has unique capability for this kind of discovery.

    CERN LHCb New
    LHCb

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

    The new particle is bound together in a similar way to protons. Due to this similarity, the Warwick researchers argue that scientists will now be able to study the particle to further understand strong interactions.

    Along with gravity, the electromagnetic interaction and weak nuclear force, strong-interactions are one of four fundamental forces. Lead scientist Professor Tim Gershon, from The University of Warwick’s Department of Physics, explains:

    “Gravity describes the universe on a large scale from galaxies to [Isaac] Newton’s falling apple, whilst the electromagnetic interaction is responsible for binding molecules together and also for holding electrons in orbit around an atom’s nucleus.

    “The strong interaction is the force that binds quarks, the subatomic particles that form protons within atoms, together. It is so strong that the binding energy of the proton gives a much larger contribution to the mass, through [Albert] Einstein’s equation E = mc2, than the quarks themselves.[3]”

    Due in part to the forces’ relative simplicity, scientists have previously been able to solve the equations behind gravity and electromagnetic interactions, but the strength of the strong interaction makes it impossible to solve the equations in the same way.

    “Calculations of strong interactions are done with a computationally intensive technique called Lattice QCD,” says Professor Gershon. “In order to validate these calculations it is essential to be able to compare predictions to experiments. The new particle is ideal for this purpose because it is the first known that both contains a charm quark and has spin 3.”

    There are six quarks known to physicists; Up, Down, Strange, Charm, Beauty and Top. Protons and neutrons are composed of up and down quarks, but particles produced in accelerators such as the LHC can contain the unstable heavier quarks. In addition, some of these particles have higher spin values than the naturally occurring stable particles.

    “Because the Ds3*(2860)ˉ particle contains a heavy charm quark it is easier for theorists to calculate its properties. And because it has spin 3, there can be no ambiguity about what the particle is,” adds Professor Gershon. “Therefore it provides a benchmark for future theoretical calculations. Improvements in these calculations will transform our understanding of how nuclei are bound together.”

    Spin is one of the labels used by physicists to distinguish between particles. It is a concept that arises in quantum mechanics that can be thought of as being similar to angular momentum: in this sense higher spin corresponds to the quarks orbiting each other faster than those with a lower spin.

    Warwick Ph.D. student Daniel Craik, who worked on the study, adds “Perhaps the most exciting part of this new result is that it could be the first of many similar discoveries with LHC data. Whether we can use the same technique, as employed with our research into Ds3*(2860)ˉ, to also improve our understanding of the weak interaction is a key question raised by this discovery. If so, this could help to answer one of the biggest mysteries in physics: why there is more matter than antimatter in the Universe.”

    The results are detailed in two papers that will be published in the next editions of the journals Physical Review Letters and Physical Review D. Both papers have been given the accolade of being selected as Editors’ Suggestions.

    [1] The Ds3*(2860)ˉ particle is a meson that contains a charm anti-quark and a strange quark. The subscript 3 denotes that it has spin 3, while the number 2860 in parentheses is the mass of the particle in the units of MeV/c2 that are favoured by particle physicists. The value of 2860 MeV/c2 corresponds to approximately 3 times the mass of the proton.

    [2] The particle was discovered in the decay chain Bs0→D0K–π+ , where the Bs0, D0, K– and π+ mesons contain respectively a bottom anti-quark and a strange quark, a charm anti-quark and an up quark, an up anti-quark and a strange quark, and a down anti-quark and an up quark. The Ds3*(2860)ˉ particle is observed as a peak in the mass of combinations of the D0 and K– mesons. The distributions of the angles between the D0, K– and π+ particles allow the spin of the Ds3*(2860)ˉ meson to be unambiguously determined.

    [3] Quarks are bound by the strong interaction into one of two types of particles: baryons, such as the proton, are composed of three quarks; mesons are composed of one quark and one anti-quark, where an anti-quark is the antimatter version of a quark.

    See the full article here.

    Warwick Campus

    The establishment of the University of Warwick was given approval by the government in 1961 and received its Royal Charter of Incorporation in 1965.

    The idea for a university in Coventry was mooted shortly after the conclusion of the Second World War but it was a bold and imaginative partnership of the City and the County which brought the University into being on a 400-acre site jointly granted by the two authorities. Since then, the University has incorporated the former Coventry College of Education in 1978 and has extended its land holdings by the purchase of adjoining farm land.

    The University initially admitted a small intake of graduate students in 1964 and took its first 450 undergraduates in October 1965. In October 2013, the student population was over 23,000 of which 9,775 are postgraduates. Around a third of the student body comes from overseas and over 120 countries are represented on the campus.

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  • richardmitnick 7:33 pm on September 21, 2014 Permalink | Reply
    Tags: , , , CERN LHCb, , ,   

    From BBC: “‘Artificial retina’ could detect sub-atomic particles” 

    BBC

    18 September 2014
    Melissa Hogenboom

    The human eye has inspired physicists to create a processor that can analyse sub-atomic particle collisions 400 times faster than currently possible.

    In these collisions, protons – ordinary matter – are smashed together at close to light speeds.

    pro
    The quark structure of the proton. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons

    These powerful smash-ups could yield new particles and help scientists understand matter’s mirror, antimatter.

    anti
    The quark structure of the antiproton

    The experimental processor could speed up the analysis of data from the collisions.

    Published in the pre-print arXiv server, the algorithm has been proposed for possible use in Large Hadron Collider (LHC) experiments at Cern in 2020. It could also be useful in any field where fast, efficient pattern recognition capabilities are needed.

    CERN LHC Grand Tunnel
    LHC

    The processor works in a similar way to the retina’s incredible ability to recognise patterns extremely quickly.
    Snapshots in time

    That is, individual neurons in our retinas are specialised to respond to particular shapes or orientations, which they do automatically before our brain is even consciously aware of what we are processing.

    pd
    Image of particle decay LHC machines produce 40 million collisions per second

    Cern physicist Diego Tonelli, one of a team of collaborators of the work, explained that the “artificial retina” detects a snapshot of the trajectory of each collision which is then immediately analysed.

    These snapshots are then mapped into an algorithm that can run on a computer, automatically scanning and analysing the charged particle trajectories, or tracks. Exposing the detector to future collisions will then allow teams sift out the interesting events.

    Data crunching

    Speed is of the essence here. There are roughly 40 million collisions per second and each can result in hundreds of charged particles.

    The scientists then have to plough through an incredible amount of data. It’s spotting the deviations from the norm that may give hints of new physics.

    lhcb
    LHCb experiment
    The LHC will be switched on again in early 2015

    An algorithm like this could therefore provide a useful way of crunching through this vast amount of data, in real time.

    “It’s 400 times faster than anything existing or foreseen for high energy physics applications. If implemented in a real experiment it will allow us to collect more interesting data more quickly,” Dr Tonelli told the BBC.

    Flavour physics

    The LHC has been switched off since February 2013 but is due to begin its hunt for new physics in 2015 when the giant machine will once again begin smashing together protons.

    As this happens, they break down and free up a huge amounts of energy that forms many neutral and charged particles. It’s the trajectories of the charged ones that can be observed.

    col
    Particle collisions
    A collision in the Large Hadron Collider creates tracks of charged particles

    The new algorithm is not aimed at the type of physics used to find the famous Higgs boson, instead it’s intended to be used for “flavour physics” which deals with the interaction of the basic components of matter, the quarks.

    Commenting on the work, Tara Shears a Cern particle physicist from the University of Liverpool, said it could be extremely useful to automatically “give us most information about what we want to study – Higgs, dark matter, antimatter and so on. The artificial retina algorithm looks like it does this brilliantly”.

    “When our detectors take these snapshots of the collisions – to us that’s like the picture that your eye sees and when your brain is scanning that picture and making sense of it, well we try and codify those rules into an algorithm that we run on computers that do the job for us automatically,” Prof Shears told the BBC’s Inside Science programme.

    “When the LHC continues… we will start to operate with a more intense beam of protons getting a much higher data rate, and then this problem of sifting out what you really want to study becomes really really pressing,” she added.

    “This artificial retinal algorithm is one of the latest steps in our mission to [understand the Universe], and it’s really good, it does the job vast banks of computers normally do.”

    The algorithm has been developed with the 2020 upgrade of the LHC in mind, which will have even more powerful collisions.

    See the full article here.

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