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  • richardmitnick 9:49 am on January 20, 2013 Permalink | Reply
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    From CMS at CERN: “Colliding different particle species: the LHC’s proton-lead run” 

    CMS Logo

    2013-01-18
    Achintya Rao

    “The new year brings a new type of collision at the LHC: the accelerator will smash protons and lead nuclei together, allowing CMS and the other LHC experiments to study the cold nuclear matter we expect these collisions to produce. Although we caught a glimpse of these asymmetric proton-lead (pPb) collisions during a pilot run last September, the next four weeks will bring the first sustained pPb run and provide valuable data. Indeed the small data sample from 2012 already revealed interesting phenomena, and raised interest in this study.

    ppb1
    A proton-lead collision at a centre-of-mass energy of 5 TeV per nucleon. In this side-on view, the proton beam enters from the right side of the image and leaves on the left; the lead beam travels in the opposite direction. The event was selected requiring a muon trigger, and the muon (red line) was reconstructed in the CSC detectors.

    For this run, CMS will combine forces with TOTEM so as to cover a greater range of collision data. The two are essentially separate entities — independent experiments that use different analysis software — and they are fully complementary. CMS measures in the central region and TOTEM exclusively measures in the very forward region.

    totem
    One arm of a TOTEM T2 detector during the installation in the interaction point

    Julia Velkovska, … a co-convener of the HI [Heavy Ions] group , explains the motivations behind colliding these different particle species together: ‘Not only does it act as a straight reference for lead collisions, but it is an interesting physics system in its own right. In addition, there are a lot of things that we think we can address now that weren’t on the cards a few months ago: the ridge we observed in the pilot run raised a lot of new questions and new approaches on how to analyse the data have been proposed.’”

    See the full article here.

    And, now “And we have Stable Beams for the pPb run!” says CMS.

    sb

    event
    Provided by Symmetry Magazine

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  • richardmitnick 12:34 pm on January 16, 2013 Permalink | Reply
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    From CERN: “Preparing the LHC for the lead-proton run” 

    16 Jan 2013
    Stephanie Hills

    For its last run before a two-year shut down, the Large Hadron Collider (LHC) is going to go beyond its design specification and collide protons with lead ions, as it did in a trial run last September.

    pb
    This small bottle contains the lead source for Linac 3, which provides lead ions for collisions in the LHC (Image: CERN)

    The LHC accelerates two counter-rotating beams of particles and brings them into collision inside detectors. The two beam pipes are contained within a single magnetic structure, where both beams experience the same strength of magnetic field. But lead ions are 208 times as heavy and have 82 times more positive charge than protons, so they respond differently to the effects of the magnets. These effects are particularly pronounced at the injection energy of 450 GeV, where in one minute protons lap the 27-kilometre LHC some 674,729 times – about eight times more often than the heavier lead nuclei.

    ‘Fortunately, the LHC has two radiofrequency systems and this means that we can tune the two beams separately,’ says accelerator physicist John Jowett. At higher energies the beams are closer in speed and the LHC team can move the proton-beam orbit about a millimetre towards the outside of the beam pipe, giving it a longer path to travel around the accelerator. The team also moves the lead beam towards the centre of the beam pipe to shorten its path. These adjustments ensure that the revolution frequencies of the separate beams become equal, so the beams collide properly in the experiments. The accelerator team is currently preparing the beams and testing the accelerator before the lead-proton run planned for later this week.

    ‘No-one has ever collided protons and lead ions successfully before, and we have just one month to do it. We have to implement a new set of operational procedures very quickly and then explore how much we can increase the beam intensities,’ says Jowett. ‘It’s going to be a challenging experimental run for the accelerator.’”

    See the original article with further links here.

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  • richardmitnick 2:11 pm on September 14, 2012 Permalink | Reply
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    From Symmetry Magazine: “First proton-lead collision test at the LHC successful” 

    For the first time, scientists at the Large Hadron Collider have collided protons with lead ions, a feat that will give them insight into the quark-gluon plasma.
    image

    September 14, 2012
    Signe Brewster

    “For most of the year, two beams of protons run the collision course around the Large Hadron Collider. Scientists take a short break from protons in winter to collide much heavier lead ions.

    In a test on Thursday, scientists collided the two types of particles together for the first time. The feat will allow physicists to better understand the conditions of the universe just after the big bang.

    LHC scientists collide lead ions to create quark-gluon plasma [qgp], a hot, dense soup of quarks that are free-floating instead of being bound into particles. They study the plasma’s properties by examining the high-energy particles that emerge from collisions that produce it.

    Early next year scientists will smash protons with lead ions to better understand results obtained from the lead-lead collisions. Proton-lead collisions are similar to lead-lead collisions, but they have lower energy and therefore do not produce quark-gluon plasma. Colliding protons with lead ions will help scientists determine which effects of the collisions come from the presence of lead ions and which ones come from the presence of the plasma.

    ‘We are all very excited that it worked so quickly,’ accelerator physicist John Jowett said. ‘This is something very new for the LHC.’

    Colliding protons with lead ions was a new challenge for the CERN teams. The two LHC beam pipes are usually filled with beams composed of identical types of particles, which are accelerated to an identical energy before colliding. Colliding lead ions with protons is unusual because lead ions have very different mass and charge than protons. Both are subject to the forces of the same magnets that surround the LHC beam pipes, so their energies and frequencies of revolution around the ring are unequal. To correct the differences, the radiofrequency cavities the beams pass through are tuned to different frequencies for each of the beams.”

    See the full article here. And, we look forward to more and greater results.


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  • richardmitnick 3:32 pm on November 15, 2011 Permalink | Reply
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    More on Heavy Ion Physics from Symmetry/Beaking 

    The making and tending of heavy ion beams for the LHC

    November 15, 2011
    Amy Dusto

    “This week the Large Hadron Collider began heavy ion physics, the process of colliding lead ions to learn about conditions in the primordial universe.

    The accelerator is expected to perform five to 10 times better than it did in its first run of these collisions last November. Although the heavy ion program will last only from now until CERN’s annual winter shutdown just after the first week of December, operators started preparations months in advance. Here symmetry breaking examines what it really takes to put lead beams in the LHC.

    The source

    Making heavy ions is more complicated than preparing the protons used in regular LHC collisions, which come from hydrogen gas. Since hydrogen atoms have only one proton and one electron each, applying a voltage to them is sufficient to rip off their electrons, leaving a load of beam-ready, positively charged protons. But the source for heavy ions, enriched lead, starts with 82 electrons. Physicists do not have miracle flypaper to grab that many subatomic particles at once, so the process takes a few steps.

    Meet Detlef Kuchler, a heavy-ion expert who tends the lead source, the first part of the heavy-ion acceleration process, by hand. He helped develop the method of extracting lead ions decades ago and can explain from memory its hundreds of associated, unlabeled diagrams. Although several people work on the source, a flowchart of what to do when things go wrong at this stage dead-ends everywhere with, ‘Call the expert.’ It may as well say, ‘Call Detlef.’ He spends a lot of nights and weekends at CERN during heavy ion season.”

    i1
    Heavy-ion expert Detlef Kuchler holds a container of lead. Image: CERN

    i2
    Kuchler prepares the oven. Image: Amy Dusto

    i3
    Operators test beams of lead ions in this linear accelerator. Image: CERN

    i4
    Operators declared “stable beams” today, which means the LHC is ready for heavy ion physics. Image: John Jowett

    See the full article here.

     
  • 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.

    i1
    CERN physicist Detlef Kuchler holds a purified sample of lead used to create heavy ions for the LHC. Photo by M. Brice / CERN

    i2
    Snapshot of two lead nuclei just after impact. Image by Henning Weber / CERN

    i3
    The CERN accelerator complex. Image: CERN

    See the full article here.

    A joint Fermilab/SLAC publication. PO Box 500 MS206, Batavia, IL 60510, USA
    i1

     
  • richardmitnick 6:44 am on June 21, 2011 Permalink | Reply
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    From CMS Times: “CMS luminosity exceeds all expectations” 

    CMS is one of four main experiments on the LHC at CERN

    “Submitted by:
    Lothar Bauerdick

    This year’s LHC physics run started in March. Since then the machine has broken many records, bringing its luminosity — the number of proton-proton collisions per second — to much higher levels than expected for this year. CMS now can take as much collision data in a single day as it accumulated during all of 2010. While taking massive amounts of new data, the CMS collaboration continues to publish new results from last year’s data set.

    i1
    The total integrated luminosity delivered to and collected by CMS until 17th June, 2011.

    The LHC team has found ways of continuously increasing the luminosity level. Because of this, we will exceed in the next few days our original luminosity goal of 1 inverse femtobarn of collision data for this run, which ends in October. We expect to get multiples of that data by the end of this run.

    The LHC now is running with over 1,000 proton bunches in each beam, and the number of protons per bunch already is approaching the machine design value. Running at such high intensities increases our productivity and scientific output, but it also brings new challenges to the experiment, such as selecting the collision events that need to be recorded and dealing with multiple collisions taking place almost simultaneously in our detector. Typical collision events not only contain overlays of interactions from several proton-proton collisions within two bunches, but also from neighbouring bunches. Despite the challenge of reconstructing these very complex events, the software and computing performance continues to be excellent and the data quality remains very high.

    Entering a new energy and luminosity regime has been very exciting. Large amounts of new data arrive every week and we analyse and scrutinise them for hints of signals beyond the expected Standard Model of physics. CMS will show its first results with this year’s data at the summer conferences, and we expect a rich harvest of exciting physics.”

    Visit CMS Times here.

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

    i1
    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.

    i1
    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.

    i1
    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

    i2
    ALICE event display

    i3
    ALICE event display at an angle

    i4
    ALICE event display with muon detector

    See the full article here.

    See the original article in SymmetryBreaking here.

     
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