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  • richardmitnick 4:49 pm on December 3, 2013 Permalink | Reply
    Tags: , , CMS, , ,   

    From CERN: “CMS presents evidence for Higgs decays to fermions” 

    CERN New Masthead

    Achintya Rao
    3 Dec 2013

    At a seminar at CERN this morning, the CMS collaboration presented several measurements of the properties of the Higgs boson. CMS showed strong evidence for the decay of Higgs bosons into fermions, corroborating CMS results shown earlier this year. CMS physicists have now measured the decay of the Higgs to pairs of bottom (b) quarks and pairs of tau leptons, with a combined significance of 4 sigma on the 5-point scale that particle physicists use to measure the certainty of a result. This significance means that the probability of a false positive is estimated to be only about one in 16,000.

    The decay to fermions is an important confirmation that the particle discovered in July 2012, with a mass of around 125 GeV, behaves like the Standard Model Higgs boson. The Higgs decays into pairs of lighter particles almost immediately after it is produced in proton collisions in the LHC. In general, particles can decay into various combinations of daughter particles. The Standard Model gives precise predictions for what the decay products are and how often they should occur.

    sm
    Standard Model of Particle Physics

    So far, the Higgs boson has been observed decaying into three types of gauge bosons: the Z, the W and the photon. The Standard Model also predicts decays to fermions – namely quarks and leptons, the fundamental particles of matter. The fermionic decays into b quarks and tau leptons are particularly strong: they are the heaviest fermions that a Higgs with a mass of around 125 GeV would decay into and are consequently the most likely fermionic decays to occur.

    Using data collected at a collision energy of 7 TeV in 2011 and at 8 TeV in 2012, CMS has now completed refined searches for tau decays with several improvements over previous analyses and found an excess in this channel corresponding to significance of 3.4 sigma. Together with earlier CMS searches for b decays that revealed a 2.1 sigma excess, excesses in the two channels have a combined significance of 4 sigma, indicating strong evidence for the Higgs decaying to fermions.

    See the full article here.

    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


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  • richardmitnick 9:23 am on October 9, 2013 Permalink | Reply
    Tags: , , , CMS, ,   

    From Livermore Lab: “U.S. scientists celebrate Nobel Prize for Higgs discovery” 


    Lawrence Livermore National Laboratory

    10/08/2013
    Donald B Johnston, LLNL, (925) 423-4902, johnston19@llnl.gov

    The Royal Swedish Academy of Sciences awarded the Nobel Prize in physics today to theorists Peter Higgs and Francois Englert to recognize their work developing the theory of what is now known as the Higgs field, which gives elementary particles mass.

    U.S. scientists, including researchers at Lawrence Livermore National Laboratory (LLNL), played a significant role in advancing the theory and in discovering the particle that proves the existence of the Higgs field, the Higgs boson.

    Nearly 2,000 physicists from U.S. institutions — including 89 U.S. universities and seven U.S. Department of Energy laboratories — participate in the ATLAS and CMS experiments, making up about 23 percent of the ATLAS collaboration and 33 percent of CMS at the time of the Higgs discovery. Brookhaven National Laboratory serves as the U.S. hub for the ATLAS experiment, and Fermi National Accelerator Laboratory serves as the U.S. hub for the CMS experiment. U.S. scientists provided a significant portion of the intellectual leadership on Higgs analysis teams for both experiments.

    Lawrence Livermore joined the Compact Muon Solenoid (CMS) experiment in 2005. LLNL contributions include: assisted in development of the trigger system that captures Higgs and other phenomena for the CMS experiment; and a leadership role in developing the software that reconstructs raw data into the physics objects that form the basis of all analyses. Lab researchers are now working on a novel physics analysis and leading a detector upgrade that can discover new particles and reveal information about the Higgs.

    cms
    Lowering of the final element (YE-1) of the Compact Muon Solenoid (CMS) detector into its underground experimental cavern.

    The LLNL team on CMS is Doug Wright, David Lange, Jeff Gronberg and postdoc Finn Rebassoo. Former LLNL postdocs currently on CMS are Jonathan Hollar (now at University of Louvain, Belgium) and Bryan Dahmes (now at University of Minnesota).

    Support for the U.S. effort comes from the U.S. Department of Energy Office of Science and the National Science Foundation.

    See the full article here.

    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security
    Administration
    DOE Seal
    NNSA

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  • richardmitnick 1:14 pm on September 6, 2013 Permalink | Reply
    Tags: , CMS, , , , ,   

    From Fermilab- “Frontier Science Result: CMS The biggest microscope” 


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

    Friday, Sept. 6, 2013
    Don Lincoln

    Fermilab Don Lincoln
    Dr. Don Lincoln

    Fermions and bosons. Mesons and baryons. Electrons and protons. Researchers of the subatomic world must know the identity and understand the behavior of dozens of different kinds of particles. However, not all particles are equal. While all are interesting in their own ways, certain ones have a more widespread utility. One such particle is the muon.

    The muon is a cousin of the electron. Like the electron, it has a negative charge and an antimatter partner with positive charge. However the muon is much heavier than the electron—more than 200 times heavier than its svelte cousin. Also, the muon is less stable, living for two millionths of a second before decaying into an electron and two neutrinos. That lifetime seems very short, but for muons traveling near the speed of light, this is long enough for them to travel hundreds of feet or even more. This means that they live long enough to hit a detector.

    While many types of post-collision particles hit a detector, interact with the atoms inside it and are absorbed, muons have a special property. Because they do not experience the strong nuclear force, muons slip by most atomic nuclei unimpeded. And because they are very heavy, they don’t easily emit photons. Thus muons can pass through a great deal of matter without stopping.

    Scientists exploit this behavior of muons to their advantage. Essentially, it makes them easy to identify. Because muons are often created in interesting collisions, they are one of the ideal particles to isolate to study all sorts of fascinating bits of physics, including, for example, the discovery of the Higgs boson. The importance of the muon is made even more evident when you recall what the CMS acronym stands for: Compact Muon Solenoid.

    cms
    Understanding the performance of your detector is critical in making important physics measurements. The muon detection system (shown in yellow and red) has been studied in great detail, resulting in a paper of more than 100 pages in length.

    CERN CMS New
    CERN’s current depiction of the CMS detector

    See the full article about muons and CMS here.

    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.


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  • richardmitnick 11:45 am on August 14, 2013 Permalink | Reply
    Tags: , CMS, , , , ,   

    From Fermilab- “From the CMS Center Work on three fronts: analysis, upgrades and simulations” 


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

    Wednesday, Aug. 14, 2013
    Kevin Burkett, deputy head of the CMS Center, wrote this column.

    “With the LHC at CERN now in the middle of a shutdown that will last until 2015, members of the CMS collaboration are hard at work on many different fronts: analyzing 2012 data, working on detector components for this shutdown and writing up the Snowmass study on the physics of the high-luminosity LHC. The rapid pace of our work means working simultaneously on the past, present and future.

    CERN LHC particles

    CMS scientists continue to harvest physics results from the LHC Run I data. One example is the recently discovered rare particle decay Bs→μμ. This result, which the CMS collaboration published simultaneously with the scientists working on the LHCb experiment, marks the culmination of more than two decades’ work from multiple collaborations in pursuit of this extremely rare process.

    Looking toward the future, two phases of upgrades are planned for the CMS detector. Fermilab personnel are key members of the teams that will implement the first phase of upgrades to the hadron calorimeter, forward pixel tracker and the trigger system after LHC Run II. The implementation of these upgrades should be completed by 2018.

    R&D is in progress for a second phase of upgrades to operate in the high-luminosity LHC (HL-LHC). We expect to complete those upgrades around 2023. With improved detectors and accelerators, the HL-LHC aims to deliver data samples over 100 times larger than what was recorded during the past run, colliding protons at the LHC design energy of 14 TeV.

    See the full article here.

    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.


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  • richardmitnick 5:24 am on July 19, 2013 Permalink | Reply
    Tags: , , CMS, , , ,   

    From CERN: “CMS and LHCb to present rare B-sub-s particle decay” 

    CERN New Masthead

    19 July 2013
    Cian O’Luanaigh

    “New results to be presented today at the European Physical Society’s High Energy Physics conference (EPS-HEP 2013) in Stockholm, Sweden, have put the Standard Model of particle physics to one of its most stringent tests to date. The CMS and LHCb experiments at CERN’s Large Hadron Collider (LHC) will present measurements of one of the rarest measureable processes in physics: the decay of a Bs (pronounced B-sub-s) particle into two muons.

    Standard model with Higgs New
    Standard Model

    The new measurements show that only a handful of Bs particles per billion decay into pairs of muons. Because the process is so rare, it is an extremely sensitive probe for new physics beyond the Standard Model. Any divergence from the Standard Model prediction would be a clear sign of something new.

    sm
    Protons collide in the CMS detector, producing a Bs particle that decays into two muons (red lines) in this event display from 2012 (Image: CMS)

    Both experiments will present results to a very high level of statistical significance (over 4 sigma for each experiment). These results are in good agreement with the Standard Model.

    ‘This is a great result for LHCb,’ says LHCb spokesperson Pierluigi Campana. ‘It’s precisely for measurements like this that LHCb was built. This result shows that we’re really putting the Standard Model to the most stringent test yet at LHC energies, and so far it’s coming through with flying colours.’

    ‘This is a process that particle physicists have been trying to find for 25 years,’ says CMS spokesperson Joe Incandela. ‘It demonstrates the incredible capability of the LHC and experiments like CMS that are able to detect such a rare process involving a particle with a mass that is roughly 1000 times smaller than the masses of the heaviest particles we are searching for now.’”

    See the full article, with links, here.

    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


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  • richardmitnick 2:22 pm on May 9, 2013 Permalink | Reply
    Tags: , , CMS,   

    From Symmetry: “Smallest lab-made drop of liquid might cause strange particle behavior” 

    A new result from the CMS collaboration takes a step toward revealing the origin of the mysterious ridge effect.

    May 07, 2013
    Kelly Izlar

    “The Large Hadron Collider is known for a list of impressive facts—it’s the world’s largest and most powerful particle collider; it accelerates particles to nearly the speed of light; its cryogenic system keeps it colder than outer space.

    Now it’s under consideration for a new superlative: Scientists there might have created the most minuscule drop of liquid ever formed in a laboratory.

    drop
    Photo: Michael Hoch / CERN

    Last year physicists collided protons with heavier lead ions in the LHC. They found a small but noticeable correspondence between the trajectories of charged particles that sped away from collisions. Newly produced particles appeared to be synced, like a school of fish moving in unison. They dubbed this phenomenon the ‘ridge effect.’

    The CMS experiment (pictured above) studied more proton–lead collisions early this year, and the result, made public this week, suggests that the particles are behaving the way they do in lead–lead collisions, where they are swept along by a drop of plasma. If this is true, the drop formed in proton–lead collisions would be the smallest drop of liquid ever formed in a laboratory.”

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.

     
  • richardmitnick 7:15 pm on April 23, 2013 Permalink | Reply
    Tags: , , CMS, , ,   

    From CERN: Fabulous Photo and “CMS prepares for the future” 

    CERN New Masthead

    23 Apr 2013
    Austin Ball, Achintya Rao

    “While the Large Hadron Collider (LHC) takes a break for its first long shutdown, the CMS collaboration are busy maintaining and consolidating the detector to be sure to handle the collider’s improved performance from 2015 onwards.

    disc 3

    The biggest priority for CMS is the tracker performance. The CMS tracking system forms the innermost subdetector and fits snugly round the LHC beampipe. It must withstand an onslaught of some 1010 particles a second and the aggressive field of mixed radiation that this produces.

    Another major element is to improve the muon detectors with a fourth endcap layer to help discriminate between interesting muons and fake signatures or background. New shielding discs, 10 centimetres deep, are to be installed on either end of the detector. Each shielding disc is made of 12 iron sector-casings filled with a special concrete. The concrete, developed for this specific application by CERN’s civil engineers, is almost 50% denser than normal concrete – it is made using haematite (or ferric oxide) instead of the usual sand – and it is loaded with boron to absorb low-energy neutrons that would otherwise give rise to unwanted hits in the detector.”

    See the full article here.

    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


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  • richardmitnick 9:25 am on April 5, 2013 Permalink | Reply
    Tags: , CMS, , , , , ,   

    From Fermilab- “Frontier Science Result: CMS CMS observes particle X” 


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

    Friday, April 5, 2013
    Jim Pivarski

    “When the discovery of a new Higgs-like particle was announced last summer, it received a lot of well-deserved media attention. It is less widely known, however, that about a dozen new particles have been discovered in the past 10 years. Why all this lack of excitement? Unlike the Higgs boson, these other new particles are bound states of quarks: the same old particles in new combinations.

    But they should not be so quickly dismissed. These new particles may be made of quarks, but most of them defy conventional explanations of how quarks fit together.

    In the standard theory of quark interactions, quarks come in three types and can only bind together in ways that would result in an equal balance of these types. By analogy with the color wheel, they are called red, green and blue, and a particle like a proton is made of one red, one green and one blue quark, which mix to form white. Antiquarks are yellow, cyan and magenta. You can form a bound state from a yellow antiquark and a blue quark, for instance, since these colors are on opposite sides of the color wheel. See this Physics in a Nutshell for more.

    proton
    A proton, composed of two up quarks and one down quark. (The color assignment of individual quarks is not important, only that all three colors be present.) (Wikipedia)

    white
    This is a nice demonstration of how you get white if you combine red, blue and green. You can try this yourself at home, or watch it demonstrated in a video online.

    Up to 2003, the only combinations of quarks and antiquarks that had ever been seen were red-green-blue particles, yellow-cyan-magenta antiparticles, and quark-antiquark pairs. Since then, a growing number of bound states have been discovered that do not fit this scheme. The first of these, discovered by the Belle experiment in Japan, was the X(3872), named “X” because we do not know what it is, and “3872″ for its mass, measured in units of MeV.

    The X(3872) and its companions might be the first examples of four-quark combinations, such as red-cyan-yellow-blue. These combinations are theoretically possible since they mix to form white, but they were not expected to be stable enough to be observed. The X(3872) in particular has a mass that is very close to the sum of two well-known bound states, D0 and D*0, so it might be a bound state of bound states. It has also been suggested that these new states are part-glueball hybrids.

    In a recent experiment, CMS scientists observed the X(3872) with a strong signal and measured several of its properties with higher precision than ever before. Far from the glare of the spotlight, these scientists are working to solve one of nature’s underappreciated mysteries.”

    cms
    In a large sample of proton-proton collisions resulting in muons and pions, a few thousand of them accumulate above the backgrounds with a mass of 3,872 MeV. This is the X(3872).

    See the original article here.

    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.


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  • richardmitnick 8:50 am on March 27, 2013 Permalink | Reply
    Tags: , , , CMS, , , ,   

    From CERN: “CMS open for business” 

    CERN New Masthead

    March 27, 2013
    Cian O’Luanaigh

    As CERN goes into its first long shutdown, it’s time open up the CMS detector and get inside for maintenance and repairs. Engineers and technicians started opening the CMS detector on 7 March, but moving the parts of this 14,000-tonne behemoth is no easy feat.

    cms
    The open side of the CMS detector, looking upwards from the cavern floor (Image: Michael Hoch/CMS)

    CMS has a barrel section made of five rings, with two endcaps each comprising three discs and, outside those discs, two 250-tonne forward hadron calorimeters (HF) [see diagram]. To open CMS, the HFs, which surround the beam pipe, are opened and lowered to the cavern floor, where they are floated on air pads into storage alcoves. Then the endcap discs are moved away from the barrel, starting with one end and then going to the other.

    ‘It took a couple of weeks of work to move the forward calorimeters and the first three discs apart,’ says detector physicist David Barney of CMS. ‘Then we went to the other end and started to move the other three discs.’

    Barney has worked on one part of CMS, the electromagnetic calorimeter (ECAL) for nearly 20 years. The ECAL is mainly made of lead tungstate crystals that detect photons and electrons. But in the endcaps, an extra detector called the preshower sits in front of the crystals. The preshower is an array of silicon sensors that measure precisely the positions of incident high-energy electrons and photons.”

    See the full article here.

    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


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  • richardmitnick 1:28 pm on March 24, 2013 Permalink | Reply
    Tags: , , , CMS, ,   

    From US/LHC Blog at Quantum Diaries: “Shutdown? What shutdown?” 

    kb
    Ken Bloom

    “The LHC has been shut down for about two months now, but that really hasn’t made anyone less busy. It is true that we don’t have to run the detector now, but the CMS operations crew is now busy taking it apart for various refurbishing and maintenance tasks. There is a detailed schedule for what needs to be done in the next two years, and it has to be observed pretty carefully; there is a lot of coordination required to make sure that the necessary parts of the detector are accessible as needed, and of course to make sure that everyone is working in a safe environment (always our top priority).

    A lot of my effort on CMS goes into computing, and over in that sector things in many ways aren’t all that different from how they were during the run. We still have to keep the computing facilities operating all the time. Data analysis continues, and we continue to set records for the level of activity from physicists who are preparing measurements and searches for new phenomena. We are also in the midst of a major reprocessing of all the data that we recorded during 2012, making use of our best knowledge of the detector and how it responds to particle collisions. This started shortly after the LHC run finished, and will probably take another couple of months.

    There is also some data that we are processing for the very first time. Knowing that we had a two-year shutdown ahead of us, we recorded extra events last year that we didn’t have the computing capacity to process in real time, but could save for later analysis during the shutdown. This ended up essentially doubling the number of events we recorded during the last few months of 2012, which gives us a lot to do. Fortunately, we caught a break on this — our friends at the San Diego Supercomputer Center offered us some time on their facility. We had to scramble a bit to figure out how to include it into the CMS computing system, but now things are happily churning away with 5000 processors in use.”

    See Ken’s complete post here.

    Participants in Quantum Diaries:

    Fermilab

    Triumf

    US/LHC Blog

    CERN

    Brookhaven Lab

    KEK


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