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  • richardmitnick 4:01 pm on August 4, 2015 Permalink | Reply
    Tags: , , CERN CMS, , , Richard Dawkins Foundation   

    From Don Lincoln via Richard Dawkins Foundation: “Physicists find surprising ‘liquid-like’ particle interactions in Large Hadron Collider” 

    Richard Dawkins Foundation

    Richard Dawkins Foundation

    FNAL Don Lincoln
    Don Lincoln

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    Rice undergraduate student Benjamin Tran, graduate student Michael Northup, postdoctoral student Maxime Guilbaud and graduate students Zhenyu Chen and Zhoudunming Tu were part of the Rice team of physicists on the Large Hadron Collider’s Compact Muon Solenoid experiment that co-authored a paper describing the unexpected particle interactions from proton and lead-nuclei collisions. Credit: Zhoudunming Tu

    Three years ago, Rice physicists and their colleagues on the Large Hadron Collider’s (LHC’s) Compact Muon Solenoid (CMS) experiment stumbled on an unexpected phenomenon.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    CERN CMS Detector
    LHC with CMS (bottom)

    Physicists smashed protons into lead nuclei at nearly the speed of light, which caused hundreds of particles to erupt from these collisions. But that wasn’t the surprise. What was surprising is where these particles went: Rather than spreading out evenly in all directions, the particles coming out of the collisions preferentially lined up in a specific direction.

    Now, the Rice team has co-authored a paper that describes the unexpected particle interactions from these proton and lead-nuclei collisions.

    Particle detectors are shaped a little like a soup can. In these kinds of collisions, there is a tendency for particles to amass in a line along the axis of the can known as a “ridge.” Up until now, physicists understood a lot about what happens when a pair of protons or a pair of lead nuclei collide, but not a lot about what happens when a proton hits a lead nucleus: Would the hot nuclear matter coming out of the collision act like protons colliding, in which the post-collision particles coast along without feeling the effect of their neighbors? Or would the particles coming out of proton and lead collisions act in a more collective, liquid-like way as in lead-nuclei collisions?

    See the full article here.

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  • richardmitnick 10:26 am on July 23, 2015 Permalink | Reply
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    From Rice: “Rice physicists find surprising ‘liquid-like’ particle interactions in Large Hadron Collider” 

    Rice U bloc

    Rice University

    July 22, 2015

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    Don Lincoln

    Three years ago, Rice physicists and their colleagues on the Large Hadron Collider’s (LHC’s) Compact Muon Solenoid (CMS) experiment stumbled on an unexpected phenomenon.

    CERN CMS Detector
    CMS

    Physicists smashed protons into lead nuclei at nearly the speed of light, which caused hundreds of particles to erupt from these collisions. But that wasn’t the surprise. What was surprising is where these particles went: Rather than spreading out evenly in all directions, the particles coming out of the collisions preferentially lined up in a specific direction.

    Now, the Rice team has co-authored a paper that describes the unexpected particle interactions from these proton and lead-nuclei collisions.

    1
    Rice undergraduate student Benjamin Tran, graduate student Michael Northup, postdoctoral student Maxime Guilbaud and graduate students Zhenyu Chen and Zhoudunming Tu were part of the Rice team of physicists on the Large Hadron Collider’s Compact Muon Solenoid experiment that co-authored a paper describing the unexpected particle interactions from proton and lead-nuclei collisions. (Photo by Zhoudunming Tu)

    Particle detectors are shaped a little like a soup can. In these kinds of collisions, there is a tendency for particles to amass in a line along the axis of the can known as a “ridge.” Up until now, physicists understood a lot about what happens when a pair of protons or a pair of lead nuclei collide, but not a lot about what happens when a proton hits a lead nucleus: Would the hot nuclear matter coming out of the collision act like protons colliding, in which the post-collision particles coast along without feeling the effect of their neighbors? Or would the particles coming out of proton and lead collisions act in a more collective, liquid-like way as in lead-nuclei collisions?

    In the recent Physical Review Letters paper, Rice physicists and co-authors returned to this mystery with more data than ever before. Physics Professor Wei Li, who discovered the phenomenon, led the team of scientists who analyzed the new data. They found that the data strongly supported that the matter coming out of these proton and lead collisions acts more like a liquid. This result was surprising because when the proton hits the lead nucleus, it punches a hole through much of the nucleus, like shooting a rifle at a watermelon (as opposed to colliding two lead nuclei, which is like slamming two watermelons together). Wei and his collaborators studied this surprising behavior by looking at six or eight particles simultaneously and how their directions correlated. This method is far more sensitive for identifying liquid-like behavior than the older method, which looked at particles two at a time. Li’s group also developed an algorithm called a trigger that records a small number of important collisions in the CMS detector among billions of candidates, allowing the researchers to efficiently investigate this interesting phenomenon.

    The data used in this analysis was recorded in March 2013 before the LHC stopped operations for refurbishments, retrofits and upgrades. This past June the LHC resumed operations with a 60 percent increase in collision energy. In December of this year, Li’s group will reconfigure the LHC accelerator to collide lead nuclei and see what sort of surprises this increase in collision energy will bring.

    This study helps scientists characterize a state of matter called a “quark-gluon plasma,” or QGP. This is similar to the familiar solid, liquid and gaseous states of matter, but much hotter. A QGP occurs when matter is heated to temperatures high enough to literally melt protons and neutrons at the center of atomic nuclei; the last time that a QGP was common in the universe was a mere millionth of a second after the Big Bang. The liquid-like nature of the QGP was a surprise to scientists, as they predicted a more gaseous-like behavior. Learning more about quark-gluon plasma will teach us something significant about the birth of the universe itself.

    See the full article here.

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    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 2:22 pm on July 16, 2015 Permalink | Reply
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    From Symmetry: “Something goes bump in the data” 

    Symmetry

    July 16, 2015
    Katie Elyce Jones and Sarah Charley

    The CMS and ATLAS experiments at the LHC see something mysterious, but it’s too soon to pop the Champagne.

    CERN CMS Detector
    CMS

    CERN ATLAS New
    ATLAS

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

    An unexpected bump in data gathered during the first run of the Large Hadron Collider is stirring the curiosity of scientists on the two general-purpose LHC experiments, ATLAS and CMS.

    CMS first reported the bump in July 2014. But because it was small and insignificant, they dismissed it as a statistical fluke. Recently ATLAS confirmed that they also see a bump in roughly the same place, and this time it’s bigger and stronger.

    “Both ATLAS and CMS are developing new search techniques that are greatly improving our ability to search for new particles,” says Ayana Arce, an assistant professor of physics at Duke University. “We can look for new physics in ways we couldn’t before.”

    Unlike the pronounced peak that recently led to the discovery of pentaquarks, these two studies are in their nascent stages. And scientists aren’t quite sure what they’re seeing yet… or if they’re seeing anything at all.

    If this bump matures into a sharp peak during the second run of the LHC, it could indicate the existence of a new heavy particle with 2000 times the mass of a proton. The discovery of a new and unpredicted particle would revolutionize our understanding of the laws of nature. But first, scientists have to rule out false leads.

    “It’s like trying to pick up a radio station,” says theoretical physicist Bogdan Dobrescu of Fermi National Accelerator Laboratory who co-authored a paper on the bump in CMS and ATLAS data. “As you tune the dial, you think you’re beginning to hear voices through the static, but you can’t understand what they’re saying, so you keep tuning until you hear a clear voice.”

    On the heels of the Higgs boson discovery in the first run of the LHC, scientists must navigate a tricky environment where people are hungry for new results while relying on data that is slow to gather and laborious to interpret.

    The data physicists are analyzing are particle decay patterns around 2 TeV, or 2000 GeV.

    “We can’t see short-lived particles directly, but we can reconstruct their mass based on what they transform into during their decay,” says Jim Olsen, a professor of physics at Princeton University. “For instance, we found the Higgs boson because we saw more pairs of W bosons, Z bosons and photons at 125 GeV than our background models predicted.”

    Considering that the heaviest particle of the Standard Model, the top quark, has a mass of 173 GeV, if this bump is real and not a fluctuation, it indicates a significantly heavier particle than those covered in 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.

    While the theories being batted around at this early stage disagree on the particulars, most agree that, so far, this data bump best fits the properties of an extended Standard Model gauge boson.

    The gauge bosons are the force-carrying particles that enable matter particles to interact with each other. The heaviest bosons are the W and Z bosons, which carry the weak force. An extended Standard Model predicts comparable particles at higher energies, heavier versions known as W prime and Z prime (or W’ and Z’). Several theorists suggest the bump at 2 TeV could be a type of W prime.

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    ATLAS data shows an increased number of W and Z boson pairs at 2 TeV. Courtesy of: ATLAS collaboration

    But LHC physicists aren’t practicing their Swedish for the Nobel ceremony yet. Unexpected bumps are common and almost always fizzle out with more data. For instance, in 2003 an international collaboration working on the Belle experiment at the KEK accelerator laboratory in Japan saw an apparent contradiction to the Standard Model’s predictions in the decay patterns of particles containing bottom quarks.

    “It was really striking,” says Olsen. “The probability that the signal was due to sheer statistical fluctuation was only about one in 10,000.”

    Seven years later, after inundating their analysis with heaps of fresh data, the original contradiction from the Belle experiment withered and died, and from its ashes arose a stronger result that perfectly matched the predictions of the Standard Model.

    But scientists also haven’t written off this new bump as a statistical fluctuation. In fact, the closer they look, the more exciting it becomes.

    With most anomalies in the data, one experiment will see it while the other one won’t—a clear indication of a statistical fluctuation. But in this case, both CMS and ATLAS independently reported the same observation. And not only do both experiments see it, they see it at roughly the same energy across several different types of analyses.

    “This is kind of like what we saw with the Higgs,” says JoAnne Hewett, a theoretical physicist at SLAC National Accelerator Laboratory who co-authored a paper theorizing the bump could be a type of W prime particle. “The Higgs just started showing up as 2- to 3-sigma bumps in a few different channels in the two different experiments. But there were also false leads with the Higgs.”

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    CMS data summarizing the search for new heavy particles decaying into several decay channels. The search reveals hints of a structure near 2000 GeV (2 TeV). Courtesy of: CMS collaboration

    Scientists are seeing more Z boson and W boson pairs popping up at 2 TeV than the Standard Model predicts. But besides this curious excess of events, they haven’t identified any sort of clear pattern.

    “Theorists come up with the models that predict the patterns we should see if there is some type of new physics influencing our experimental data,” Olsen says. “So if this bump is new physics, then our models should predict what else we should see.”

    Even though this bump is far too small to signify a discovery and presents no predictable pattern, its presence across multiple different analyses from both CMS and ATLAS is intriguing and suspicious. Scientists will have to patiently wait for more data before they can flesh out what it actually is.

    “We will soon have a lot more data from the second run of the LHC, and both experiments will be able to look more closely at this anomaly,” Arce says. “But I think it would almost be too lucky if we discovered a new particle this soon into the second run of the LHC.”

    The latest results from these two studies will be presented at the European Physical Society conference in Vienna at the end of the month.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • 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.

    See the full article here.

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    Fermilab Campus

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

     
  • richardmitnick 12:53 pm on March 27, 2015 Permalink | Reply
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    From CMS at CERN/LHC: “CMS is never idle” 

    CERN New Masthead

    2015-03-27
    André David and Dave Barney

    CERN CMS New II

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    Before proton collisions take place again at the LHC, the CMS detector has been looking at the result of collisions of cosmic particles high up in the atmosphere. This event display shows the track of a muon that reached the CMS detector 100 m underground and passed through the muon chambers (in red) and the silicon tracker (in yellow). Muons as this one are used to calibrate the detector in advance of proton collisions.

    CMS is eager to see the first collisions of the LHC Run2. The recent news that the LHC restart may be delayed because of a hardware issue gives us extra time to prepare for those collisions. Far from being idle waiting for collisions, CMS is busy taking advantage of other types of collision.

    CMS is never idle. Without beams, the data-taking does not stop: collisions of cosmic particles high up in the atmosphere produce showers of particles, including muons. Some of these muons have high enough energies to penetrate through the 100 m of ground over the CMS detector and traverse it, leaving behind a trail of dots in our detectors. By connecting the dots, we can learn where the different detector components are inside the huge volume (~3700m3) of CMS to better than a millimetre. This is very important because the whole detector was taken apart and put back together in preparation for Run2. With the cosmic ray muons, we can also synchronise the different detectors down to one hundred-millionth of a second, given that cosmic muons interact with many detectors as they cross the experiment. After a long shutdown, we are also coming back to operating the experiment 24 hours a day, 7 days a week. There is always a shift crew operating and monitoring the experiment, an larger crew of experts that stand ready to intervene in case issues arise, and an even larger community that checks the quality of the data collected. So we exploit this cosmic debris to understand out detectors to the needed precision to later find again the Higgs boson and possibly new, as-yet undiscovered, particles; the more cosmic muon signals we record and analyse, the better prepared we will be to tackle proton collisions at 13 TeV.

    See the full article here.

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    Meet CERN in a variety of places:

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    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE
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    CMS
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    LHCb
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  • richardmitnick 11:18 am on February 13, 2015 Permalink | Reply
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    From FNAL- “Frontier Science Result: CMS “ 

    FNAL Home


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

    Friday, Feb. 13, 2015
    FNAL Don Lincoln
    Don Lincoln

    1
    Scientists in the CMS collaboration look for many different possible signatures that would reveal new physical phenomena. One interesting idea is massive and long-lived particles that stop inside the detector and then decay. [This is the whole picture. Not well done by FNAL.]

    CERN CMS New
    CMS

    “We are all agreed that your theory is crazy. The question that divides us is whether it is crazy enough to have a chance of being correct.”

    This quote is attributed to Niels Bohr speaking to Wolfgang Pauli when the latter was presenting a new theory in a seminar, but it works equally well when modern scientists make presentations about new theories to try to push forward our understanding of the cosmos. While there is no question that the Standard Model has been an enormous success, there remain unsolved mysteries.

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    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 early successes of the LHC have stringently constrained theoretical ideas that have been put forward as possible advances in our understanding of the rules of the universe. This leads scientists to think more creatively.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    One such crazy idea (but is it crazy enough?) is that there exist very heavy and stable particles that can be created only in large accelerators like the LHC. Unlike most subatomic particles, which decay in less than the blink of an eye, these particles could persist for long times, ranging from microseconds to years.

    A number of theories make these predictions, and one originates in supersymmetry. All supersymmetric theories predict that there exists a set of particles that we’ve not yet discovered, although the different theories make quite different predictions as to the masses of these undiscovered particles.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    An example of a supersymmetric theory that predicts long-lived particles is one in which the bosons have a very high mass, while the fermions have a very low mass. One of these fermions is the gluino, which is the supersymmetric analog of the gluon, a boson in the Standard Model.

    There are some requirements on the decay product of the gluino. Since the gluino carries color (the charge of the strong force) it must decay into a particle that also carries color. In the Standard Model, this would be a quark. And since the gluino is a supersymmetric particle, it must also have a supersymmetric decay particle. But since its supersymmetric partner would be massive, as all supersymmetric bosons are, the gluino cannot easily decay. The net result is that, under these conditions, the gluino could live for quite a long time.

    If such a particle exists and can be produced at the LHC, some of them will be produced with such a low velocity that they will interact with the CMS detector and stop moving, much as a ball rolling over a beach eventually stops. And, once stopped, the particle will eventually decay inside the detector. To be able to better identify these decays, scientists looked inside the detector in periods when no beam passed through it. Using the data, they were able to search for and set limits on long-lived particles with lifetimes ranging from a millionth of a second to more than fifteen minutes.

    So we’re left with the question: The theory is crazy, but is it crazy enough? Hopefully with the resumption of LHC operations later this year, we’ll finally find out.

    See the full article here.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

     
  • richardmitnick 1:40 pm on February 6, 2015 Permalink | Reply
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    From CERN: “Everything is illuminated” 

    CERN New Masthead

    Feb 2, 2015
    Katarina Anthony

    On Monday, 26 January, CMS installed one of the final pieces in its complex puzzle: the new Pixel Luminosity Telescope. This latest addition will augment the experiment’s luminosity measurements, recording the bunch-by-bunch luminosity at the CMS collision point and delivering high-precision measurements of the integrated luminosity.

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    Installing the PLT in the heart of the CMS experiment.

    No matter the analysis, there’s one factor that every experimentalist needs to know perfectly: the luminosity. Its error bars can make or break a result, so its high precision measurement is vital for success. With this in mind, the CMS collaboration tasked the BRIL (Beam Radiation Instrumentation and Luminosity) project with developing a new detector to record luminosity for Run 2. Working with experimentalists from across the CMS collaboration and CERN, BRIL designed, created and installed the small – but mighty – Pixel Luminosity Telescope (PLT).

    “During Run 1, our primary online luminosity measurements came from the forward hadron calorimeter, which we compared to the offline luminosity measurement using the pixel detector,” says Anne Dabrowski, BRIL deputy project leader and technical coordinator (CERN). “But as we move to higher and higher luminosities and pile-ups in Run 2, extracting the luminosity gets harder to do.” That’s where the PLT comes in. Designed with the new LHC Run 2 in mind, the PLT uses radiation-hard CMS pixel sensors to provide near-instantaneous readings of the per-bunch luminosity – thus helping LHC operators provide the maximum useful luminosity to CMS. The PLT is unconnected to the CMS trigger and reads out at 40 MHz (every 25 ns) with no dead-time.

    The BRIL team includes collaborators from CERN, Germany, New Zealand, the USA, Italy and Russia.

    Research and development on the PLT began ten years ago, with diamonds first considered for the pixel telescope planes. A PLT prototype was even installed along the LHC beam line during Run 1. “Diamond sensors would have been an excellent choice, as they do not need to be run at low temperatures to have an acceptable radiation damage signal loss,” says David Stickland, BRIL project leader (Princeton University). However – while the potential for a diamond PLT remains – the prototype results led the team to use a more tested and reliable material for Run 2: silicon.

    However, this practical decision would create new issues for the BRIL team to resolve: “Suddenly, heat was a real concern,” explains Anne. “If we wanted to get a good signal out of silicon sensors, we had to bring the telescopes down in temperature.” With only 18 months to go until installation, the BRIL team had to go back to the drawing board to try and fit a cooling structure into an already-constrained space.

    The PLT is comprised of two arrays of eight small-angle telescopes situated on either side of the CMS interaction point. Each telescope hovers only 1 cm away from the CMS beam pipe, where it uses three planes of pixel sensors to take separate, unique measurements of luminosity. (Image: A. Rao)

    “We were successful thanks to the ingenuity of the CMS engineering integration office and PH-DT engineers, in particular Robert Loos,” says David. “Rob designed an extraordinary 3D-printed cooling structure using a titanium alloy, using the ‘selective laser melting (SLM)’ technique in order to ‘grow’ the cooling structure we needed.” Despite the internal diameter of the cooling channels being less than 3 mm, the cooling structure can make right-angle turns at the drop of a dime and withstand pressure up to 15 bar. “It’s tremendously strong, light and compact. I don’t know how it could have been made without this technique,” David adds.

    This is only the first example of the innovative design used by the BRIL group. So while the telescope’s installation may be complete, our coverage of their work is not yet over. Look out for an article in the next edition of the Bulletin to find out more…

    See the full article here.

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    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries

     
  • richardmitnick 11:53 am on January 27, 2015 Permalink | Reply
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    From CERN: “CMS pins down Higgs with first run data” 

    CERN New Masthead

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    New results from the CMS collaboration are pinning down the properties of the Higgs boson (Image: Maximilien Brice/CERN)

    27 Jan 2015
    André David

    With the Large Hadron Collider (LHC) preparing to restart in a few months, data from its first run has already been bearing fruit.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    A recent publication by the CMS collaboration brings together the broadest set of results to date about the properties of the Higgs boson. The paper, submitted to The European Physical Journal C (and available at arXiv:1412.8662) showcases what CMS physicists have learnt about the particle using data taken between 2011 and 2012 Together with another paper on the spin and parity of the boson, [arXiv:1411.3441] the results draw a picture of a particle that – for the moment – cannot be distinguished from the Standard Model predictions for the Higgs boson.

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    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 particle physics is a theoretical framework that explains how the basic building blocks of matter interact, governed by four fundamental forces. Developed in the early 1970s, it has successfully explained almost all experimental results and precisely predicted a wide variety of phenomena – including the mass of the Higgs boson.

    The CMS experiment recently combined measurements from different decays of the Higgs to extract the most precise measurement of its mass to date: 125.02±0.30 GeV, with a relative uncertainty of 0.2%. This uncertainty can be split into a systematic component (±0.15 GeV) and a statistical component (±0.26 GeV), which provides excellent prospects for Run 2 to yield an even more precise mass measurement, as more data will reduce the statistical component.

    The Higgs boson is the final piece of the Standard Model – when it was discovered by the CMS and ATLAS experiments in 2012, it was the last particle predicted by the Model to be verified experimentally.

    CERN ATLAS New
    ATLAS

    But with all parameters now experimentally constrained, physicists can use the Model to make even more specific predictions. For example, having measured the mass of the Higgs boson, the Standard Model makes unambiguous predictions as to what the Higgs boson’s other properties should be. Some, such as the boson’s spin (zero), parity (positive), and electric charge (neutral) stem directly from the symmetries of the Standard Model. But others, such as the strength with which the Higgs boson interacts (or couples) with other Standard Model particles are harder to check.

    The Higgs boson decays to many different particles, including photons, Z bosons, W bosons, tau leptons, b quarks and muons. Checking how the Higgs decays into these particles, and with what probabilities, will allow physicists to complete the picture and gain a better understanding of the Higgs.

    Finding no significant deviations with the Standard Model has set the bar high for the LHC’s Run 2. Theorists and experimentalists will continue working together to find a small wrinkle in the so far smooth Higgs boson picture. That small wrinkle that may point the way out of the Standard Model oasis, across the desert, and the as-yet unknown physics beyond. It’s going to be an exciting Run 2.

    See the full article here.

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  • richardmitnick 10:20 am on November 14, 2014 Permalink | Reply
    Tags: , , CERN CMS, , , ,   

    From FNAL- “Frontier Science Result: CMS Origin of the smallest masses” 


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

    Friday, Nov. 14, 2014
    Jim Pivarski

    Since the discovery of the Higgs boson two years ago, about 80 analyses have helped to pin down its properties. Today, we know that it does not spin, that it is mirror-symmetric, and that it decays into pairs of W bosons, pairs of Z bosons, pairs of tau leptons, and pairs of photons (through a pair of short-lived top quarks). There are even weak hints at a fifth decay mode: decays into pairs of b quarks. All of these results are in agreement with expectations for a Standard Model Higgs boson, but they are still coarse measurements with significant uncertainties.

    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.

    To say that this boson is a Standard Model Higgs is to say that it is exactly the particle that was predicted in 1964. That leaves a lot of room for surprises. Without interference from new phenomena, the rate that this boson decays into particle-antiparticle pairs would be proportional to the square of the mass of the particle-antiparticle pairs. The best way to check the proportionality of something is to look at it on an extreme range. Since the Higgs is believed to give mass to everything from 0.0005-GeV electrons to 173-GeV top quarks, there’s plenty of room to check.

    dots
    Muons (red) are 18 times lighter than tau leptons (blue), so we expect Higgs decays to muon pairs to be about 300 times less common than Higgs decays to tau pairs.

    The highest decay rates are easiest to detect, so only the heaviest particle-antiparticle pairs have been tested so far. The lightest particle-antiparticle decay that has been observed is Higgs to pairs of tau leptons, which are 1.8 GeV each. The next-lighter final state that could be observed is Higgs to pairs of muons, which are 0.1 GeV each. By the expected scaling, Higgs to muon pairs should be 300 times less common. However, muons are easy to detect and clearly identify, so they make a good target.

    Even if you combine all the LHC data collected so far, it would not be enough to see evidence of this decay mode. However, the LHC is scheduled to restart next spring at almost twice its former energy. Higher energy and more intense beams would produce more Higgs bosons, making a future detection of Higgs to muon pairs possible.

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

    To prepare for such a discovery and find potential problems early, CMS scientists searched for Higgs to muon pairs in the current data set. They didn’t find any, but they did establish that no more than 0.16 percent of Higgs bosons decay into muons, only a factor of 7 from the expected number, and then they used these results to project sensitivity in future LHC data. Incidentally, the Higgs boson is the first particle known to decay into tau lepton pairs much more (6.3 percent) than muon pairs (0.023 percent). All other particles decay into taus and muons almost equally.

    CERN CMS New
    CMS in the LHC at CERN

    They also searched for Higgs decays into electrons, the lighter cousin of muons and tau leptons. Since electrons are 200 times lighter than muons, Higgs to electron pairs is expected only 0.00000051 percent of the time. None were found, though an observation would been an exciting surprise!

    See the full article here.

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  • richardmitnick 10:31 am on October 31, 2014 Permalink | Reply
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    From FNAL- “Frontier Science Result: CMS Boosted W’s” 


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

    Friday, Oct. 31, 2014

    FNAL Don Lincoln
    Don Lincoln

    Today’s article covers an interesting topic. It’s interesting not because it explores new physics, but because of how it reveals some of the mundane aspects of research at the LHC. It also shows how the high energy of the LHC makes certain topics harder to study than they were during the good old days at lower-energy accelerators.

    At the LHC, quarks or gluons are scattered out of the collision. It’s the most common thing that happens at the LHC. Regular readers of this column know that it is impossible to see isolated quarks and gluons and that these particles convert into jets as they exit the collision. Jets are collimated streams of particles that have more or less the same energy as the parent quark or gluon. Interactions that produce jets are governed by the strong force.

    map
    In the green region, we show what a W boson looks like before it decays. Moving left to right, the boson is created with more and more momentum. In the yellow region, we repeat the exercise, this time looking at the same W boson after it decays into quarks, which have then turned into jets. Finally in the pink region, we look at a jet originating from a quark or gluon. This looks much like a high-momentum W boson decaying into quarks. Because ordinary jets are so much more common, this highlights the difficulty inherent in finding high-momentum W bosons that decay into jets.
    No image credit

    Things get more interesting when a W boson is produced. One reason for this is that making a W boson requires the involvement of the electroweak force, which is needed for the decay of heavy quarks. Thus studies of W bosons are important for subjects such as the production of the top quark, which is the heaviest quark. W bosons are also found in some decays of the Higgs boson.

    A W boson most often decays into two light quarks, and when it decays, it flings the light quarks into two different directions, which can be seen as two jets.

    But there’s a complication in this scenario at the LHC, where the W bosons are produced with so much momentum that it affects the spatial distribution of particles in those two jets. As the momentum of the W boson increases, the two jets get closer together and eventually merge into a single jet.

    As mentioned earlier, individual jets are much more commonly made using the strong force. So when one sees a jet, it is very hard to identify it as coming from a W boson, which involves the electroweak force. Since identifying the existence of W bosons is very important for certain discoveries, CMS scientists needed to figure out how to tell quark- or gluon-initiated jets from the W-boson-initiated jets. So they devised algorithms that could identify when a jet contained two lumps of energy rather than one. If there were two lumps, the jet was more likely to come from the decay of a W boson.

    CERN CMS New
    CMS

    In today’s paper, CMS scientists explored algorithms and studied variables one can extract from the data to identify single jets that originated from the decay of W bosons. The data agreed reasonably well with calculations, and the techniques they devised will be very helpful for future analyses involving W bosons. In addition, the same basic technique can be extended to other interesting signatures, such as the decay of Z and Higgs bosons.

    See the full article here.

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