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  • richardmitnick 7:20 am on August 10, 2013 Permalink | Reply
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    From CERN: “The amazing world of smashed protons and lead ions” 

    CERN New Masthead

    In the CERN Bulletin
    Issue No. 33-35/2013 – Monday 12 August 2013
    Antonella Del Rosso

    alice

    “When a single proton (p) is smashed against a lead ion (Pb), unexpected events may occur: in the most violent p-Pb collisions, correlations of particles exhibit similar features as in lead-lead collisions where quark-gluon plasma is formed. This and other amazing results were presented by the ALICE experiment at the SQM2013 conference held in Birmingham from 21 to 27 July.

    event
    Event display from the proton-lead run, in January 2013. This event was generated by the High Level Trigger (HLT) of the ALICE experiment.

    Jet quenching is one of the most powerful signatures of quark-gluon plasma (QGP) formed in high-energy lead-lead collisions. QGP is expected to exist only in specific conditions involving extremely hot temperatures and a very high particle concentration. These conditions are not expected to apply in the case of less ‘dense’ particle collisions such as proton-lead collisions. ‘When we observe the results of these collisions in ALICE, we do not see a strong particle-jet suppression; however, when studying the most violent p-Pb collisions we observe signatures in particle production characteristic of a hydrodynamic nature,’ explains Mateusz Ploskon from the ALICE collaboration. ‘Indeed, some of the properties of the correlations of particles produced in proton-lead collisions resemble those associated with the formation of QGP in lead-lead collisions.’

    More data is needed to resolve the conundrum but in the meantime the physics community is excited as the phenomena observed in proton-lead collisions could have strong implications for our understanding of the QCD – the theory that describes the interactions of strongly interacting subatomic particles. ‘The p-lead data already provide an extremely useful baseline for the collisions of heavy ions; however, we need more time and more data to understand the intriguing observations from proton-lead collisions – it remains to be seen whether we learn something new about hadronic and nuclear collisions at high energies, and whether these observations have any unexpected implications for our understanding of QGP based on lead-lead collisions,’ says Mateusz.”

    See the full article here.

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  • richardmitnick 10:29 am on July 31, 2013 Permalink | Reply
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    From CERN: “ALICE through a gamma-ray looking glass” 

    CERN New Masthead

    31 July 2013
    Christine Sutton

    “The ALICE experiment at CERN specializes in heavy-ion collisions at the LHC, which can produce thousands of particles. In analysing this maelstrom, the researchers need to know exactly how material is distributed in the detector – and it turns out that the LHC’s simpler proton–proton collisions can help.

    layers
    A gamma-ray view of the layers of the ALICE detector. (Image: ALICE)

    Gamma-rays produced in the proton–proton collisions, mainly from the decays of neutral pions, convert into pairs of electrons and positrons as they fly through matter in the detector. The origin of these pairs can be accurately detected, providing a precise 3D image that includes even the inaccessible innermost parts of the experiment. The process is almost exactly the same as in 1895 when Wilhelm Röntgen produced an X-ray image of his wife’s hand – the inner parts of the body could be seen for the first time without surgery. The main difference lies in the energy of the radiation – ten times greater for the gamma rays in ALICE than for Röntgen’s X-rays. Importantly for the ALICE experiment, it allows the team to check crucial simulations.”

    See the full article here.

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  • richardmitnick 2:04 pm on March 21, 2013 Permalink | Reply
    Tags: ALICE, , , , , , ,   

    From ALICE at CERN: “ALICE 20th Anniversary” 

    CERN New Masthead

    THERE IS A TON OF UNEXPLAINED JARGON IN THIS ARTICLE. IT IS REALLY WRITTEN EXPECTING SPECIALISTS TO BE THE READERS. BUT I OFFER IT FOR ANYONE WHO MIGHT KNOW WHAT IS GOING ON OR WHO MIGHT WISH A STARTING POINT TO DIG IN AND FIND OUT.

    21 March 2013
    Panos Charitos

    20 years ago ALICE started its amazing adventure in the wonderland of strong interactions and the study of extraordinary forms of matter like the Quark Gluon Plasma.

    CERN’s ion programme has a long history and was initiated in 1986 with the acceleration of oxygen ions at 60 and 200 GeV/nucleon, and continued with sulphur ions at 200 GeV/nucleon up to 1993. The first Lead-ion beams at 160 GeV/nucleon became available in 1994. The accelerating chain for 16O and 32S consisted of an ion source of the electron–cyclotron resonance (ECR) type, a radio-frequency quadrupole (RFQ) pre-accelerator, the linear accelerator injector (LINAC I), the PSBooster , the PSand the SPS. For the acceleration of lead ions, a new ECR source, a new RFQ and a new LINAC had to be constructed. The results of the light-ion programme strongly supported its continuation with heavier-ion beams. In particular, the energy densities reached during the collisions appeared to be high enough to be interesting, and many of the suggested signatures for the onset of a quark–gluon plasma phase turned out to be experimentally accessible. The experience gained was instrumental in assessing the feasibility of experiments with lead ions and for indicating the necessary detector modifications. Seven experiments participated in the lead-age adventure.

    Following the previous successes of the heavy-ion physics programme at CERN the idea of a heavy-ion dedicated experiment that would study lead-lead collisions at the new energy scale of the LHC was discussed. During the previous years, the experience gained was instrumental in assessing the feasibility of experiments with lead ions and for indicating the necessary detector modifications that were needed to move with the lead-age adventure at the new scale of the LHC.

    The first appearance of ALICE was in the Evian meeting back in 1992. Jurgen Schukraft recalls that: “We had to do enormous extrapolations because the LHC was a factor of 300 higher in centre-of-mass energy and a factor of 7 in beam mass compared with the light-ion programme, which started in 1986 at both the CERN SPS and the Brookhaven AGS.” A Letter of Intent for a new experiment at the LHC was submitted on 1 March 1993 to the LHC Committee that was formed shortly after the Evian meeting. It marks the first official use of the name ALICE and it was signed by 230 people coming from 42 institutes around the world. It was clearly describing the proposal of the ALICE Collaboration for building a dedicated heavy-ion detector to exploit the unique physics potential of nucleus-nucleus interaction at LHC energies and where the formation of a new phase of matter, the quark gluon plasma is expected. The submission of the letter of intent was followed by a detailed technical proposal that was submitted two years later in 1995 and shortly endorsed by the LHCC and the CERN management.

    early

    mega

    ALICE studies strong interactions by using particles – created inside the hot volume of the Quark Gluon Plasma as it expands and cools down – that live long enough to reach the sensitive detector layers located around the interaction region. The physics programme at ALICE relies on being able to identify all of them – i.e. to determine if they are electrons, photons, pions, etc – and to determine their charge. This involves making the most of the different ways that particles interact with matter. Over twenty years, ALICE has developed a wide range of R&D activities, confronted many challenges in designing and building new detectors that could cope with the physical challenges at the new energy scales. One should also refer to the big data challenge as heavy-ion collisions produce petabytes of data that need to be stored and later analysed in order to get new physics results.

    event

    Following the first run, ALICE successfully reported on the formation of QGP and offered a new insight on the nature of strong interacting matter at extreme densities. The existence of such a phase and its properties are a key issue in QCD for the understanding of confinement and of chiral-symmetry restoration. Wherever you look, from the energy loss of fast quarks to quarkonia, from the details of the dynamical evolution of the system to the very first study of charmed hadrons and the loss of energy, the interplay between , to name just a few, the ALICE results stand out for their quality and relevance. Following the recent proton-lead run that opens new horizons for the heavy-ion community at CERN, ALICE is now looking forward to a series of upgrades during the LS1.

    Paolo Giubellino notes: ‘This has been the result of many years of work and dedication of all of us, and we can all be proud of now sharing this remarkable harvest. It has been an enormous effort, but we can now say it was really worth it, and all share the happiness for this wealth of results. We all contributed to this accomplishment, and we should all draw from it even more motivation to go forward for the next many years to come!'”

    See the full article here.

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  • richardmitnick 8:46 am on March 20, 2013 Permalink | Reply
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    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 3:00 pm on December 17, 2012 Permalink | Reply
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    From Symmetry: “Scientists already planning for LHC long shutdown” 

    September 10, 2012 Re-posted 12.17.12 by Symmetry
    Signe Brewster

    Next year, scientific collaborations will take full advantage of the Large Hadron Collider’s time without beam.

    “The Large Hadron Collider will go into a long shutdown early next year to allow scientists and technicians to prepare it for higher collision energy in 2015. It has been running at 7 TeV; scientists plan for it to reemerge at upward of 13 TeV. Beginning in February of 2013, highly coordinated teams will spend 20 months preparing its equipment for the change. Higher luminosity means more particle collisions, and the experiments will need more advanced equipment to keep up. With the detectors the most accessible they have been since their original construction, the four big LHC experiments will take the opportunity to perform upgrades and routine repairs. The collaborations already have plans for the new year.

    man at cern

    ALICE
    Alice Icon New
    The ALICE experiment focuses on collisions of heavy ions to study the conditions present just after the big bang. The collisions produce a quark-gluon plasma, a hot soup in which quarks travel freely instead of being bound into particles. They also produce high-energy quarks and gluons that interact with the plasma and then fragment into jets of particles and gamma rays.

    ALICE will install a new part to a system that records the energy of particles. The new Di-Jet Calorimeter will broaden the experiment’s ability to measure the energy of individual gamma rays. Scientists can study an individual gamma ray to infer the energy of the quark from which it was emitted. That way, they can study how the quark-gluon plasma affects the energy of the quark and resulting jet of particles.

    ATLAS
    AtlasExperiment

    ATLAS will add a fourth layer of pixels, known as the Insertable B-Layer, to its pixel detector. The increased number of pixels will enable measurements at a location closer to where particle collisions occur and allow scientists more accurately to identify jets of particles produced from bottom quarks.

    Identifying these particles is important in the search for the Higgs boson, which, according to the Standard Model, frequently decays into bottom quarks. The ATLAS and CMS experiments discovered a Higgs-like particle this summer.

    CMS

    CMS Logo

    The LHC experiments cannot record data from every single collision that occurs, so they select or discard this information at a split second’s notice using automatic triggers. At higher luminosity, the experiments will deal with more collisions and therefore will need better trigger systems.

    During the long shutdown, the CMS experiment plans to add a new layer to their muon detector, which will help them to decide which collisions are worth studying.

    LHCb

    LHCB Icon

    LHCb’s most important project during the shutdown will be to replace a segment of beam pipe and its support structures. The new pipe will be able to withstand temperature changes and radiation better, and the lighter support structure will reduce background in the detector.

    LHCb will also begin to prepare for the next planned shutdown, in 2018, when they will install an upgrade to their detector.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.

     
  • richardmitnick 1:01 pm on November 29, 2012 Permalink | Reply
    Tags: ALICE, , , , , , , , ,   

    From ALICE at CERN via Quantum Diaries: “The coolest and hottest fluid” 


    Pauline Gagnon

    “The ALICE experiment is dedicated to the study of the quark-gluon plasma. Each year, the LHC operates for a few weeks with lead ions instead of protons. ALICE collects data both during proton-proton collisions and heavy ions collisions. Even when only protons collide, the projectiles are not solid balls like on a billiard table but composite objects. By comparing what can is obtained from heavy ion collisions with proton collisions, the ALICE physicists must first disentangle what comes from having protons in a bound state inside the nucleus as opposed to “free protons”.

    qgp

    So far, it appears that the quark-gluon plasma only formed during heavy-ion collisions since they provide the necessary energy density over a substantial volume (namely, the size of a nucleus). Some of the effects observed, such as the number of particles coming out of the collisions at different angles or momenta, depend in part on the final state created. When the plasma is formed, it reabsorbs many of the particles created, such that fewer particles emerged from the collision.

    By colliding protons and heavy ions, scientists hope to discern what comes from the initial state of the projectile (bound or free protons) and what is caused by the final state (like the suppression of particles emitted when a quark-gluon plasma forms).

    ppg
    A “snapshot” of the debris coming out of a proton-lead ion collision captured by the ALICE detector showing a large number of various particles created from the energy released by the collision.

    The ultimate goal is to study the so-called ‘structure function’, which describes how quarks and gluons are distributed inside protons, when they are free or embedded inside the nucleus.

    More will be studied during the two-month running period with protons colliding on heavy ions planned for the beginning of 2013.”

    See the full article here.

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  • richardmitnick 5:12 pm on March 16, 2012 Permalink | Reply
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    From CERN: “The LHC and its successors” 

    Anaïs Schaeffer
    2012-03-12

    “In one year, the LHC will begin to change. During the first long shutdown, from December 2012 to late 2014, the machine will go through a first phase of major upgrades, with the objective of running at 7 TeV per beam at the beginning of 2015.

    With this long technical stop and the two others that will follow (in 2018 and 2022), a new project will see the light of day. Current plans include the study of something that looks more like a new machine rather than a simple upgrade: the High Luminosity LHC (HL-LHC). Much more powerful than the current machine, the HL-LHC will aim for a very high production rate of events for the ALICE, ATLAS, LHCb and CMS detectors. ‘On the machine side, the HL-LHC project has been approved and should be co-funded as a study by the EU,’ says Oliver Bruning, Leader of the Accelerators and Beam Physics Group (ABP) of BE Department HL-LHC Deputy Project Leader and Accelerator Study Leader of LHeC. ‘On the experiments’ side, teams are now working on the technical design reports. This part has not been approved yet, and the funds are still to be found.’ If everything goes well, the HL-LHC could be ready to start running in around 2020.

    In the meantime, engineers and physicists have begun to work on another project, which could be built in parallel to the HL-LHC. Called LHeC, it will be designed for collisions between electrons and protons. ‘The LHeC could be implemented in two different ways,’ explains Frank Zimmermann, member of the BE/ABP Group and Deputy EuCARD Coordinator. ‘The first one would be to build an electron ring in the LHC tunnel, on the top of the current one – leading to what physicists call a ring-ring machine. The second solution would be to build a separate tunnel of about 9 km that would host two superconducting LINACs in a racetrack Energy Recovery LINAC (ERL) configuration where the two LINACs are connected via return arc. The electron beam would be accelerated in three passages through each LINAC, before electron-proton collisions would occur at the highest energy in the LHC.’ In both cases, the electron and proton beams would cross at a unique point, where a new experiment would need to be installed.”

    Excited? See the full article here.

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  • richardmitnick 1:52 pm on February 4, 2012 Permalink | Reply
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    From ALICEMatters: “EMCal Teams Finish Installation Of Their ‘Particle Thermometer’ “ 

    Amy Dusto
    03 February 2012

    “Scientists on the ALICE experiment just completed the installation of a crucial component for tracking high-energy particle jets. Without it, physicists would be lacking critical tools to select which events out of billions to store and analyse.

    Engineers and physicists around the world worked intensively over five years to complete the electromagnetic calorimeter, or EMCal. The United States, supported by the Department of Energy’s Nuclear Physics Office, contributed 70% of the project costs. Scientists installed the last two pieces of the 80-ton device on January 18th.


    [A correction to the factual content: Although Peter Jacobs explains that the EMCal modules being were made in the USA, there is also a side project to make additional modules in Chin,a for an upgrade during the long LHC shutdown. This will be carried out by Chinese colleagues.]

    The EMCal’s heft comes from its many sheets of lead absorbers, which it needs to stop particles coming from collisions in the detector in order to measure their energy. “The calorimeter measures the energy of individual photons and electrons,” said ALICE physicist Peter Jacobs. “It’s a sort of particle thermometer.”

    The ALICE detector’s calorimeter was specifically designed to study the most complex collisions at the Large Hadron Collider (LHC), those created using beams of heavy ions. These collisions recreate Big-Bang-like conditions and produce events with many more particles than the LHC’s usual collisions using beams of protons.

    CERN typically smashes lead ions together each November. These collisions produce a gloopy mixture, known as the quark-gluon plasma (QGP), in the centre of ALICE. Occasionally, a very energetic quark or gluon, called a jet, will also be created in the collision. When this happens, the QGP gets in its way, and that interaction is important for researchers seeking to understand material which first existed in the earliest moments of the universe. The EMCal allows ALICE to select and record the rare events containing such jets, and to measure their properties precisely.

    ae

    A second arm of the EMCal will be added to ALICE during the long LHC shutdown in 2013.

    The two pieces of the EMCal scientists installed this year were small; they add only about 10 percent to the calorimeter’s overall coverage, Jacobs said. However, all the small parts do add up — every new measurement gets us a little closer to the heart of the matter.”

    See the full article here.

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  • richardmitnick 10:35 am on January 24, 2012 Permalink | Reply
    Tags: ALICE, , , , , , ,   

    From ALICE at CERN via Symmetry/Breaking: “Scientists finish installation of 80-ton ‘particle thermometer’ at ALICE detector” 

    “Scientists on the ALICE experiment at the Large Hadron Collider just completed the installation of a crucial component for tracking high-energy particle jets. Without it, physicists would be lacking crucial tools to select which events out of billions to store and analyze.

    Engineers and physicists around the world worked intensively over five years to complete the electromagnetic calorimeter, or EMCal. The United States, supported by the Department of Energy’s Nuclear Physics Office, contributed 70 percent of the project costs. Scientists installed the last two pieces of the 80-ton device on Jan. 18.

    The EMCal’s heft comes from its many sheets of lead absorbers, which it needs to stop particles coming from collisions in the detector in order to measure their energy. “The calorimeter measures the energy of individual photons and electrons,” said ALICE physicist Peter Jacobs. “It’s a sort of particle thermometer.”

    EMCal

    i3
    Scientists install the electromagnetic calorimeter at the ALICE detector. Image: CERN

    See the full post here.

     
  • richardmitnick 2:22 pm on October 3, 2011 Permalink | Reply
    Tags: ALICE, , , , , ,   

    From Quantum Diaries: Paul Gagnon on Why the LHC? 

    “There are bosos and bosons, and if the Large Hadron Collider (LHC) were built only to find the Higgs boson, you would be absolutely right to think all physicists belong to the first category. But the fact is, the LHC does much more than search for Higgs bosons.

    Despite the media focusing mainly on the Higgs boson, this search only represents one of the many aspects we hope to cover with the LHC. Granted, the Higgs boson brings such an elegant solution to the problem of the origin of mass that its high popularity among physicists has reached even the general public.

    But the LHC could be opening the door to parallel worlds, extra dimensions or the discovery of as many new particles as the ones we already know. These are but some of the exciting questions we are trying to address.”

    Paul is a good writer. Please visit his post.
    He points to dark matter, asymmetry, the various experiments at CERN, ATLAS, ALICE, CMS, LHCb. He points to galaxy movement. This is a nice overview piece.Check it out.

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