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  • richardmitnick 12:56 pm on October 3, 2014 Permalink | Reply
    Tags: , , , , Heavy Ion Physics, , , ,   

    From FNAL- “Frontier Science Result: CMS Subatomic hydrodynamics” 


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

    Friday, Oct. 3, 2014
    This column was written by Don Lincoln
    FNAL Don Lincoln
    Dr. Don Lincoln

    It’s hard for most people to imagine what it’s like at the heart of a particle collision. Two particles speed toward one another from opposite directions and their force fields intertwine, causing some of the particles’ constituents to be ejected. Or possibly the energy embodied in the interaction might be high enough to actually create matter and antimatter. It’s no wonder the whole process seems confusing.

    crash
    The same basic equations that govern the flow of water are important for describing the collisions of lead nuclei. In today’s article, we’ll get a glimpse of how this works.

    Things get a little easier to imagine when the particles are the nuclei of atoms (note that I said easier, not easy). For collisions between two nuclei of lead, one can imagine two small spheres, each containing 208 protons and neutrons, coming together to collide. Depending on the violence of the collision, some or many of the protons and neutrons might figuratively melt, releasing their constituent quarks so they can scurry around willy-nilly. Physicists call this form of matter a quark-gluon plasma, and it acts much like a liquid.

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

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

    Part of this liquid-like behavior is due to the fact that so many particles are involved. An LHC collision between two lead nuclei might involve thousands or tens of thousands of particles. Because these particles are quarks and gluons, they experience the strong nuclear force. So as long as they are close enough to each other, the particles interact strongly enough that they clump a bit together. The net outcome is that the flow of particles from collision between lead nuclei looks vaguely like splashes of water. In these cases, the equations of hydrodynamics apply. Mathematical descriptions like these have been used to make sense of other features we see in LHC collisions between lead nuclei.

    glu
    In Feynman diagrams, emitted gluons are represented as helices. This diagram depicts the annihilation of an electron and positron.

    However, there is more to understand. We can imagine collisions between the collective 416 protons and neutrons of lead nuclei as splashes of water, but when a pair of protons collide, the collision doesn’t yield enough particles to exhibit hydrodynamic behavior. So as the number of particles involved goes down, the “splash” behavior must slowly go away. In addition, in the first studies of lead nuclei collisions, only the grossest features of the collision were studied. This is because it is impossible to identify individual quarks and gluons.

    There are ways to dig into these sorts of questions. One way is to look at collisions in which one beam is a proton and the other is a lead nucleus. This is a halfway point between the usual LHC proton-proton collisions and the lead-lead ones. In addition, we can turn our attention to quarks that we can unambiguously identify, such as bottom, charm and strange quarks, to better understand the hydrodynamic behavior.

    In this study, physicists looked at particles containing strange quarks. Since strange quarks don’t exist in the beam protons, studying them gives a unique window into the dynamics of lead-lead collisions. By combining studies of particles with strange quarks in lead-lead and lead-proton collisions, scientists hope to better understand the complicated and liquid-like behavior that is just beginning to reveal its secrets.

    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 8:46 am on March 20, 2013 Permalink | Reply
    Tags: , , , , Heavy Ion Physics,   

    From CERN ALICE: "How ALICE was born’" 

    CERN New Masthead

    20 March 2013
    Hans H.Gutbrod

    Alice Icon New

    “In 1982 a MoU was signed by GSI, Darmstadt, CERN and LBL Berkeley to get heavy ions to CERN: GSI promised to bring an ECR-ion source and LBL a RFQ Linac to the CERN site. Rudolf Bock(GSI), Herrmann Grunder (LBL) and Reinhard Stock (Uni Marburg) and others proposed to have heavy ions in the CERN PS. Robert Klapisch, then research director of CERN, found SPS more adequate and this lead to heavy ion physic[s] with Oxygen beams in 1986, sulphur beams in 1987 and lead beams in 1994.
    sps
    The Super Proton Synchrotron

    In 1983 at the relativistic heavy ion meeting at Brookhaven, I discussed with Carlo Rubbia topics of the future heavy ion collider at BNL, later called RHIC, when he told me: ‘You will get your collider at CERN, with enough energy for your physics case’

    A few years later, a proposal for a heavy-ion programme was submitted in the LHC project . Rubia, kept his promise and among many things he insisted on a two-in-one magnet solution for the LHC instead of a pp_bar mode with only one vacuum chamber (what’s the benefits of this architecture? One vacuum chamber and one magnet is only good for ppbar, an option several persons preferred since it was also cheaper ).

    From 1991 on, a group of about 20 persons met at CERN regularly to work on a proposal for a dedicated heavy ion experiment at the LHC. In parallel we had to build and run our lead beam experiments at the SPS. “

    And, so it goes in HEP. Read the full article here.

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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 1:42 pm on December 20, 2012 Permalink | Reply
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    From CMS at CERN: “CMS observes melting of Upsilon particles in heavy-ion collisions” 

    CMS Logo

    “In 2011, CMS presented early evidence that Upsilon (Υ) particles produced in lead-lead collisions ‘melt’ as a consequence of interacting with the hot nuclear matter created in these heavy-ion interactions. CMS has since updated and extended this result using additional data collected in the 2011 heavy-ion run, and the observation now has a significance of greater than 5σ (or 5 standard deviations), the gold standard for claiming a discovery in high-energy physics.”

    event

    image

    Candidate Υ decay to two muons observed in a lead-lead collision at the LHC. The two red lines (tracks) are the two muons, the mass of orange lines are tracks from other particles produced in the collision, whose energy is measured in the electromagnetic calorimeter (red cuboids) and the hadron calorimeter (blue cuboids)

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  • richardmitnick 9:32 am on September 12, 2012 Permalink | Reply
    Tags: , , Heavy Ion Physics   

    From ALICE Matters: “ALICE experiment sets record for the hottest spot in the Universe” 

    icon

    qm12

    11 September 2012
    Panos Charitos

    “In the recent Quark Matter 2012 conference, the ALICE collaboration announced the production of the highest human-made temperature in the universe. The highest temperature of approximately 5.5 trillion Kelvin was produced at the Large Hadron Collider at CERN by smashing heavy ions after accelerating them to 99% of the speed of light. Although more data processing is needed to convert the measured energy to an exact temperature it is believed that this would be more than 5 trillion Kelvins. Paolo Giubellino said: ‘«It’s a very delicate measurement. Give us a few weeks and it’ll be out’. That’s about 38% hotter than the old record, set by the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, New York, by smashing gold ions together.”

    See the full article here.

    “The ALICE Collaboration has built a dedicated heavy-ion detector to exploit the unique physics potential of nucleus-nucleus interactions at LHC energies. Our aim is to study the physics of strongly interacting matter at extreme energy densities, where the formation of a new phase of matter, the quark-gluon plasma, is expected. The existence of such a phase and its properties are key issues in QCD for the understanding of confinement and of chiral-symmetry restoration. For this purpose, we are carrying out a comprehensive study of the hadrons, electrons, muons and photons produced in the collision of heavy nuclei. Alice is also studying proton-proton collisions both as a comparison with lead-lead collisions and in physics areas where Alice is competitive with other LHC experiments.”

    alice

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  • richardmitnick 7:38 pm on July 19, 2012 Permalink | Reply
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    From Brookhaven Lab: “Hot Nuclear Matter Featured in Science” 

    Brookhaven Lab

    Prelude to new RHIC/LHC findings to be presented at Quark Matter 2012

    July 19, 2012
    Karen McNulty Walsh

    A review article appearing in the July 20, 2012, issue of the journal Science describes groundbreaking discoveries that have emerged from the Relativistic Heavy Ion Collider (RHIC) at the U.S. Department of Energy’s Brookhaven National Laboratory, synergies with the heavy-ion program at the Large Hadron Collider (LHC) in Europe, and the compelling questions that will drive this research forward on both sides of the Atlantic. With details that help enlighten our understanding of the hot nuclear matter that permeated the early universe, the article is a prelude to the latest findings scientists from both facilities will present at the next gathering of physicists dedicated to this research — Quark Matter 2012, August 12-18 in Washington, D.C.

    rh
    RHIC’s two large experiments, STAR and PHENIX, have multiple detector components and complex electronics for tracking and identifying the particles that fly out after ions collide at nearly the speed of light.

    This Brookhaven article then proceeds to provide us with what looks to be the article from The Journal Science.

    See the full Brookhaven article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

    i1

     
  • richardmitnick 6:49 pm on March 20, 2012 Permalink | Reply
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    From Princeton Plasma Physics Lab: “PPPL delivers a plasma source that will enable high-power beam pulses in a new Berkeley Lab accelerator” 

    i1

    Princeton Plasma Physics Lab

    March 19, 2012
    John Greenwald

    “Scientists at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have designed and delivered a crucial component for a device that can heat a spot of foil to 30,000 degrees Centigrade in less than a billionth of a second. The part will complete a linear accelerator that researchers at the E.O. Lawrence Berkeley National Laboratory are using to create a superheated state called “warm dense matter.

    For PPPL physicist Erik Gilson, the plasma source he designed for the accelerator marks the third generation of components that he has created for Berkeley Lab projects that are part of the Heavy Ion Fusion Science Virtual National Laboratory, a joint venture of PPPL, Berkeley Lab, and Lawrence Livermore National Laboratory.

    i3
    Erik Gilson with a copper-clad module and chamber for testing the units.
    (Photo credit: Elle Starkman, PPPL Office of Communications)

    See the full very interesting article here.


     
  • 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 2:16 pm on November 11, 2011 Permalink | Reply
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    From ALICE Matters: Heavy Ion Beams 

    Amy Dusto
    11 November 2011

    On Monday November 14th the LHC begins heavy ion physics, the process of colliding lead ions, to learn about conditions in the primordial universe. The accelerator is expected to perform 5 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 on December 8th, preparations began months in advance. Amy Dusto, from the blog symmetry breaking, reports for ALICE Matters on 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 208 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.”

    ii
    From 2010 Heavy Ion season

    i2
    Event display from a lead-lead collision recorded by ALICE (6.11.2011)

    Read the full post here.

     
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