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  • richardmitnick 8:08 pm on October 20, 2011 Permalink | Reply
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    From Symmetry Magazine via SymmetryBreaking: “Accelerator soup: Scientists to mix elements in LHC to study recipe for heavy-ion collisions” 

    Instead of colliding two beams of protons or two beams of much heavier lead ions, as the LHC usually does, operators will try to collide one of each in the coming weeks. On October 31, they will test the process for 16 hours, and two weeks later they’ll get another 24. That’s all the time they decided they could take from the precious month of data-collecting they will give the experiments during the upcoming lead-lead run. If it works, a proton-lead ion research program could be in place for November 2012.

    The scientists undertaking the task of colliding protons and lead want to collect benchmark information about single beams of lead ions to get a better picture of what’s going on in lead-lead collisions. For that, the tiny proton acts as a probe of the more massive lead ion.

    Theorist Urs Wiedemann explained that it’s a bit like making soup. A meticulous chef wants to know exactly what happens at each step of a recipe. This includes both the initial state of the individual ingredients – onions sautéed or raw? – as well as the final outcome inside the pot. Otherwise the chef can’t make informed changes. Similarly a physicist needs to know the individual properties of both of the elements he or she wants to collide, as well as what their smashing produces, in order to get the full picture for analysis.

    CERN physicist Detlef Kuchler holds a purified sample of lead used to create heavy ions for the LHC. Photo by M. Brice / CERN

    Snapshot of two lead nuclei just after impact. Image by Henning Weber / CERN

    The CERN accelerator complex. Image: CERN

    See the full article here.

    A joint Fermilab/SLAC publication. PO Box 500 MS206, Batavia, IL 60510, USA

  • richardmitnick 11:31 am on May 27, 2011 Permalink | Reply
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    From Fermilab Today: “Tempest in a pinpoint” 

    A proton contains two up quarks, a down quark and a soup of quark-antiquark pairs, seething below the surface.

    A CMS Result

    “It is often said that a proton is made of three quarks: two of the same type, called up quarks, and one of a different type called a down quark. But that’s not the whole story. In the space between these three stable quarks there is a boiling soup of quark–antiquark pairs. That is, a quark and an antimatter quark spontaneously come into existence, drift a while, and then recombine, destroying one another. This happens all the time— in every proton in every atom of every cell of our bodies, and in all of the matter in the universe.

    When two protons collide in the LHC, most of the individual quarks miss each other. Often only one quark or antiquark from each proton collides directly. When an up quark collides with an anti-down quark, the two can combine to form a W+ boson; similarly, a down quark and an anti-up quark can combine to form a W¯ boson. In both cases, an antiquark is involved. Thus, each of the millions of W bosons produced at the LHC must come from at least one of these transient particles, caught before it had a chance to sink back into the soup.”

    Fermilab is one of several remote location centers for the CMS Collaboration.

    See the full article here.

  • richardmitnick 2:53 pm on May 23, 2011 Permalink | Reply
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    From The CMS Collaboration at CERN: “CMS presents results from LHC heavy-ion collisions” 

    23rd May, 2011

    “The CMS collaboration is presenting its latest results this week at the annual Quark Matter conference, held this year in Annecy, France. The results are based on analyses of data collected during the LHC’s heavy-ion run in the last two weeks of 2010 and early proton runs in 2011, both of which were conducted at an energy of 2.76 TeV per nucleon pair.

    A striking result from CMS concerns the propagation of particles known as Upsilons through the soup-like Quark-Gluon Plasma, thought to have existed during the first microseconds of the Universe.

    See the full article here for a full explanation.

  • richardmitnick 2:11 pm on May 23, 2011 Permalink | Reply
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    From CERN: “LHC experiments present new results at Quark Matter 2011 Conference” 

    “The three LHC experiments that study lead ion collisions all presented their latest results today at the annual Quark Matter conference, held this year in Annecy, France. The results are based on analysis of data collected during the last two weeks of the 2010 LHC run, when the LHC switched from protons to lead-ions. All experiments report highly subtle measurements, bringing heavy-ion physics into a new era of high precision studies.

    Events recorded by the ALICE experiment from the first lead ion collisions (Nov-Dec 2010).

    ‘ These results from the LHC lead ion programme are already starting bring new understanding of the primordial universe,’ said CERN Director General Rolf Heuer. ‘ The subtleties they are already seeing are very impressive.’

    In its infancy, just microseconds after the Big Bang, the universe consisted of a plasma of quarks and gluons (QGP), the fundamental building blocks of matter. By colliding heavy ions, physicists can turn back time and recreate the conditions that existed back then, allowing us to understand the evolution of the early universe.”

    See the full article from CERN here.

    The LHC heavy-ion programme builds on experiments conducted over a decade ago at CERN’s Super Proton Synchrotron (SPS) accelerator, which saw hints that the plasma could be created and studied in the laboratory. Then, in 1999, the baton passed to the Relativistic Heavy-Ion Collider (RHIC) at the US Brookhaven National laboratory, which firmly established that QGP could be created on a miniscule scale. This year’s Quark Matter conference is the first in the series to feature results from the LHC.

  • richardmitnick 2:07 pm on May 12, 2011 Permalink | Reply
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    From US/LHC: “ALICE Event Display – Decoded” 

    Want to understand the ALICE event display better? Look at http://www.uslhc.us/LHC_Decoded/ALICE_Event_Display_-_Decoded.

    Kathryn Grim

    Most of the time, the Large Hadron Collider accelerates protons, particles so tiny they fit inside of atoms. But for about a month each year, the scientists load the LHC with something a bit heartier: lead ions.

    Of the four detectors at the LHC, only ALICE was designed specifically to study these types of collisions. Scientists rely on the different parts of the ALICE detector to study how matter formed after the big bang.

    Heavy-ion collisions in the LHC can create quark-gluon plasma, a phase of matter scientists think occurred in nature only during the first millionths of a second of the universe’s birth. In this state, protons and neutrons melt into a hot soup of their constituent pieces, quarks and gluons.

    Members of the ALICE collaboration want to study the quark-gluon plasma to learn more about the first few moments that shaped our universe. The many components of the ALICE detector give them the information they need.

    Read about:

    1: Silicon tracker
    2: Time projection chamber
    3: Electromagnetic calorimeter
    4: Transition radiation detector
    5: Photon spectrometer
    6: Muon detector

    ALICE event display

    ALICE event display at an angle

    ALICE event display with muon detector

    See the full article here.

    See the original article in SymmetryBreaking here.

  • richardmitnick 2:35 pm on March 23, 2011 Permalink | Reply
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    From The US/LHC Blog: “Why run at lower energy?” 

    Posted by Christine Nattrass on 23 Mar 2011

    “Right now the LHC is about to start a short run with proton-proton collisions at a center of mass energy 2.76 TeV. This is lower than what we ran last year and is a special request from the heavy ion physicists. So you’ve heard a lot about why the particle physicists want to go to higher energy. But why do we heavy ion physicists want to go to lower energy?
    We want a reference for our lead-lead collisions. If nucleus-nucleus collisions were nothing but a bunch of proton-proton collisions, what we measure in lead-lead collisions should be just some constant times what we measure in proton-proton collisions. This is a bit simplistic, but it’s a pretty good start.

    Read Christine’s full post here.

  • richardmitnick 9:40 pm on March 22, 2011 Permalink | Reply
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    From The US/LHC Blog: “LHC FTW !!!” 

    At The US/LHC Blog

    Check it out at the above link.

  • richardmitnick 12:12 pm on January 25, 2011 Permalink | Reply
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    From CERN Courier: “ATLAS observes striking imbalance of jet energies in heavy ion collisions” 

    “The ATLAS experiment has made the first observation of an unexpectedly large imbalance of energy in pairs of jets created in lead-ion collisions at the LHC (G Aad et al. 2010). This striking effect, which is not seen in proton–proton collisions, may be a sign of strong interactions between jets and a hot, dense medium (quark-gluon plasma) formed by the colliding ions.

    “Concentrated jets of particles are formed in the head-on (central) collisions of lead ions at the LHC. The jets materialize from the hadronization of quarks and gluons scattered from the protons and neutrons in the colliding ions. If a quark-gluon plasma is formed in the collisions of the high-energy ions, then as the jets materialize they will traverse this hot, dense medium. In so doing they should lose energy to the medium through multiple interactions, in a process called jet quenching (CERN Courier September 2003 p17).

    The jets are most often produced in pairs (dijets) travelling in opposite directions with equal transverse energies, but if the jets travel different distances before escaping the medium, then their energies will no longer be equal. Experiments at the Relativistic Heavy Ion Collider at Brookhaven observed signs of this effect in single-particle distributions; however, the result from ATLAS represents the first direct observation of energy loss by jets, and the first in which the effect is visible on an event-by-event basis.

    Read the full article here.

  • richardmitnick 12:15 pm on December 17, 2010 Permalink | Reply
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    From The CMS Collaboration at CERN’s LHC:”CMS sees Z’s in collisions of Pb” 

    Slow news day, so, how about a neat graphic from CERN’s CMS Collaboration at the LHC?

    Taken 41 minutes ago, “CMS has an important first: detection and measurement of decays that appear to be from Z bosons inside the primordial fireballs that result from lead ion collisions. Here, two electrons emerge from the quark-gluon plasma and deposit their energy in the electromagnetic calorimeter. The tall red tower in the lower left of the image and the shorter red double tower on the upper right indicate an electron-positron pair that can be reconstructed to have come from a single Z-boson candidate.” (Credit: Copyright CERN on behalf of the CMS Collaboration.)


    CMS detector

    * Size: 21 m long, 15 m wide and 15 m high.
    * Weight: 12 500 tonnes
    * Design: barrel plus end caps
    * Location: Cessy, France

    “The CMS experiment uses a general-purpose detector to investigate a wide range of physics, including the search for the Higgs boson, extra dimensions, and particles that could make up dark matter. Although it has the same scientific goals as the ATLAS experiment, it uses different technical solutions and design of its detector magnet system to achieve these.

    The CMS detector is built around a huge solenoid magnet. This takes the form of a cylindrical coil of superconducting cable that generates a magnetic field of 4 teslas, about 100 000 times that of the Earth. The magnetic field is confined by a steel ‘yoke’ that forms the bulk of the detector’s weight of 12 500 tonnes. An unusual feature of the CMS detector is that instead of being built in-situ underground, like the other giant detectors of the LHC experiments, it was constructed on the surface, before being lowered underground in 15 sections and reassembled.

    More than 2000 scientists collaborate in CMS, coming from 155 institutes in 37 countries (October 2006).”

  • richardmitnick 2:44 pm on December 16, 2010 Permalink | Reply
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    Duke Physics and the LHC 

    Duke Theorists Begin Analyzing Exciting New Data from LHC

    Yet another great US institution contributing to the work of analyzing data from the LHC at CERN.

    Professors Steffen Bass and Berndt Mueller rejoiced this month at the news that the Large Hadron Collider started its program of collisions of lead nuclei at unprecedented energies, almost 15 times higher than those previously explored at Brookhaven National Lab’s Relativistic Heavy Ion Collider (RHIC). The Large Hadron Collider (LHC) is at the European Organization for Nuclear Research (CERN) near Geneva, Switzerland.

    The lead nuclei are being collided as part of three large international experiments at the LHC called ALICE, ATLAS and CMS which seek to create a quark-gluon plasma, a state of matter that is believed to have existed microseconds after the birth of our universe.




    Read the full article here. Way to go Blue Devils!

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