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  • richardmitnick 9:25 pm on August 30, 2013 Permalink | Reply
    Tags: , ATLAS, , , , , ,   

    From CERN: “A 3D photograph with 92 million pixels for tagging particles” 

    CERN New Masthead

    Mon 02 Sep 2013
    Antonella Del Rosso

    “Where was a given particle born? How can we tag it precisely enough to be able to then follow it along its track and through its decays? This is the job of the pixel detector installed at the heart of the ATLAS detector, only centimeters away from the LHC collisions. In order to improve its identification and tagging capabilities, the ATLAS collaboration has recently taken a big step towards the completion of the upgrade of its Pixel detector, which will include the insertion of a brand-new layer of 12 million pixels.

    pipe
    The 7 metre long beryllium beam pipe inserted in the carbon-fibre positioning tool is being prepared ready for the new innermost layer of the Pixel detector to be mounted. (Photo courtesy ATLAS Collaboration)

    With its three layers and 80 million channels concentrated in 2.2 square metres, the ATLAS pixel detector was already the world’s largest pixel-based system used in particle physics. Its excellent performance was instrumental in the discovery of the Higgs boson in July 2012. However, already at the time of its design, the collaboration had decided to add a fourth layer at a later stage. With the LHC running at full steam, the ATLAS collaboration very quickly decided to go for a tighter schedule and have the new detector installed by the restart of the LHC in 2014. “The tight schedule was a challenge for all the teams involved in the project,” says Beniamino Di Girolamo, ATLAS Technical Coordinator. “About 40 members of the ATLAS collaboration from several institutes worked – and are still working – very hard to meet the deadlines but nothing would have been possible without the help of CERN’s vacuum experts.”

    Indeed, in order for the beam pipe to be inserted into the experiment’s structure, it had to be made smaller. The cylindrical tube used up to that point was too large and the new Pixel detector component would not fit inside the existing structure. This was a job for the Vacuum group in the Technology Department (TE-VSC). “In order to redesign the beam pipe for the ATLAS collision point we first had to consult several other groups, including collimation, machine protection and impedance experts,” explains Mark Gallilee, project leader for the TE VSC group responsible for beam pipes for the experiments. “The requirements of the ATLAS beam pipe were very specific. Because of the limited space we had to reduce the thickness of the aerogel layer, which thermally insulates the tube. We also had to develop a new type of removable vacuum flange so that the vacuum chamber could be removed from the new smaller space if necessary.”

    At the beginning of August an important part of the job was completed with the insertion of the new beam pipe into the Pixel detector support structure. ‘During this operation, we had very little clearance and the different parts had to slide and move within a few millimetres. In some cases, we only had a 2 mm clearance and we had to align all the components with a precision of 10 microns,’ says Didier Ferrère, deputy project leader for the new Pixel detector. In addition to the mechanical issues, the ATLAS experts also had to resolve some critical thermal issues. ‘230 degrees are needed to activate the NEG that ensures the correct level of vacuum in the beam pipe, while our Pixel detector operates at a temperature of around -20 degrees,’ says Didier Ferrère. ‘We have run tests and simulations and are confident that the two environments – the new module and the new beam pipe – are compatible.’

    The result is worth the effort. The new ATLAS pixel system will be able to provide physicists with 40 million ‘3D snapshots’ every second, with an accuracy of 92 million pixels. ‘It will be an amazing tool for us,’ says Didier Ferrère.”

    pd
    Pixel Detector
    The ATLAS Pixel Detector provides a very high granularity, high precision set of measurements as close to the interaction point as possible. The system provides three precision measurements over the full acceptance, and mostly determines the impact parameter resolution and the ability of the Inner Detector to find short lived particles such as B-Hadrons. The system consists of three barrels at average radii of ~ 5 cm, 9 cm, and 12 cm (1456 modules), and three disks on each side, between radii of 9 and 15 cm (288 modules). Each module is 62.4 mm long and 21.4 mm wide, with 46080 pixel elements read out by 16 chips, each serving an array of 18 by 160 pixels. The 80 million pixels cover an area of 1.7 m^2. The readout chips must withstand over 300 kGy of ionising radiation and over 5×10^14 neutrons per cm^2 over ten years of operation. The modules are overlapped on the support structure to give hermetic coverage. The thickness of each layer is expected to be about 2.5% of a radiation length at normal incidence. Typically three pixel layers are crossed by each track. The pixel detector can be installed independently of the other components of the ID. In the starting phase, only two of the three layers planned for will be installed. Copyright CERN 2009 — ATLAS Experiment

    See the full article here.

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  • richardmitnick 3:43 pm on March 12, 2013 Permalink | Reply
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    From CERN: “ATLAS releases animated particle plots” 

    CERN New Masthead

    No Date
    No Writer credit

    This set of animated plots show data from the ATLAS detector as used in searching for a Higgs boson.

    In making these plots, the ATLAS physicists start with the hypothesis that proton-proton collisions in the LHC can produce Higgs bosons, which in turn decay to other particles. For the plot at the far right, they searched through the data they collected, focusing on proton-proton collisions that yielded pairs of high-energy photons, whose energies they measured with calorimeters in the ATLAS detector.

    If the two photons were produced by the transformation of a single particle, the mass of that particle can be calculated from the energy of the photons and the angle between their two directions. In most cases, the photons came from other sources, so the mass value forms a smooth “background” – the number of photon pairs expected for a given number of proton-proton collisions at a given energy. The expected background level is shown as the blue line on the plot.

    If there is a new particle, more photon pairs than expected appear above the background at a mass corresponding to the particle’s mass. Watch the animation of the plot on the far right here to see a bump eventually emerge out of the background data – the “signal” from a Higgs-like particle in the mass region around 126 GeV. The black dots show the data and reveal how a small but significant effect can emerge as more and more data are analysed.

    See the full article here.

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  • richardmitnick 10:03 am on March 12, 2013 Permalink | Reply
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    From Brookhaven Lab via Quantum Diaries: “Polarized Proton Data Flowing With RHIC Running” 

    This post was written by Brookhaven Lab scientists Shigeki Misawa and Ofer Rind.

    “Run 13 at the Relativistic Heavy Ion Collider (RHIC) began one month ago today, and the first particles collided in the STAR and PHENIX detectors nearly two weeks ago. As of late this past Saturday evening, preparations are complete and polarized protons are colliding with the machine and detectors operating in physics mode,’ which means gigabytes of data are pouring into the RHIC & ATLAS Computing Facility (RACF) every few seconds.

    Brookhaven RHIC
    RHIC at Brookhaven

    CERN ATLAS New
    CERN ATLAS at the LHC

    Today, we store data and provide the computing power for about 2,500 RHIC scientists here at Brookhaven Lab and institutions around the world. Approximately 30 people work at the RACF, which is located about one mile south of RHIC and connected to both the Physics and Information Technology Division buildings on site. There are four main parts to the RACF: computers that crunch the data, online storage containing data ready for further analysis, tape storage containing archived data from collisions past, and the network glue that holds it all together. Computing resources at the RACF are split about equally between the RHIC collaborations and the ATLAS experiment running at the Large Hadron Collider in Europe.”

    two men
    Shigeki Misawa (left) and Ofer Rind at the RHIC & ATLAS Computing Facility (RACF) at Brookhaven Lab

    There is a lot going on here. See the full article here.

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  • richardmitnick 8:13 am on February 20, 2013 Permalink | Reply
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    From CERN: “ATLAS in 2012: Building on success” 

    CERN New Masthead

    atlas
    A view of the ATLAS detector taken during the 2012 end-of-year technical stop (Image: ATLAS/CERN)

    20 Feb 2013
    Christine Sutton

    “Last year was both exciting and highly productive for the physicists working on the ATLAS experiment at the Large Hadron Collider (LHC). They not only discovered a particle that could be the long-sought Higgs boson – as did their colleagues on the CMS experiment – but also announced many results based on searches for signs of new physics and on refined precision measurements.

    Highlights included new limits on possible dark-matter particles and on the new particles predicted by theories that go beyond the Standard Model by including supersymmetry. Precision measurements on Standard Model processes also yielded interesting results in their own right, in addition to providing important information to aid the hunt for the Higgs boson. They allowed detailed studies of the production of top quarks and antiquarks, and of the phenomenon of CP-violation in Bs mesons.

    Standard Model Large
    Standard Model with “Higgs”

    Meanwhile, more detailed knowledge of the new boson awaits the analysis of all of the data from 2012, which continues apace.

    Read more: “ATLAS in 2012: Building on success” – CERN Courier

    See the full article here.

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  • richardmitnick 8:59 pm on January 16, 2013 Permalink | Reply
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    From BBC: “The Hunt for the Higgs: A Horizon Special” 

    I was hunting around the BBC looking for something else when I came upon an excellent video originally broadcast in January 2012. While it is one year old, and while the question of the Higgs boson is probably very close to being answered*, still this video presents a valuable lesson.

    Our host is Prof JIM AL-KHALILI, OBE, Professor of Theoretical Physics and Chair in the Public Engagement in Science at the University of Surrey.

    JA
    Prof Jim Al-Khalili

    The video is especially valuable because it ventures into the LHCb Collaboration at CERN’s incredible LHC.

    lhcb

    In this section on the LHCb experiment, the subjects of Broken Symmetry and the theory, to date untested, of Supersymmetry are explored. These subjects were not at all present in the PBS Frontline piece The Atom Smashers (2008), nor the BBC video The Big Bang Machine(2008).

    If you use either the Opera browser or Firefox, there are excellent video download utilities for saving an .mp4 in at least 720p HD.

    I hope that you will enjoy the video and might add it to your collection.

    The BBC page for the video is here.

    *On July 4, 2012 The General Director of CERN, Rolf-Dieter Heuer, announced that both the ATLAS and CMS collaborations had discovered a new particle with a degree of certainty [beyond five Σ (sigma)] which placed the find beyond doubt. The particle was a boson. But, there was not then and there is still not now certainty that the find was the Higgs boson. That has yet to be confirmed. This confirmation might wait until the completion of the International Linear Collider.

     
  • 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 11:34 am on July 20, 2012 Permalink | Reply
    Tags: ATLAS, , , , , , , , , , ,   

    From Fermilab Today: “CMS Result – Would the real Higgs boson please stand up?” 


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

    Friday, July 20, 2012
    Jim Pivarski

    After decades of speculation, the Higgs boson was finally discovered on the fourth of July, 2012 – or was it? Despite the headlines, scientists claimed to have seen not a Higgs boson, but “a new particle” or “a new boson.” As it often happens in science, the eureka moment is an explosion of more questions than answers.

    image
    Higgs image from ATLAS

    image2
    Higgs image from CMS

    What the experiments actually revealed was an excess of certain types of events. More collisions produced pairs of photons, pairs of Z bosons or pairs of W bosons than would be expected in a world without a Higgs. The photon and the Z boson measurements were precise enough to show that they came from decays of a single particle with a mass of approximately 125 GeV (heavier than all known particles except the top quark). The photon, Z and W are all bosons, which are particles of force, as contrasted with fermions, which are particles of matter. Fermions attract or repel each other by tossing and catching bosons.”

    See the full and well articulated article here.

    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.

     
  • 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 1:45 pm on February 21, 2012 Permalink | Reply
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    From Ken Bloom of USLHC via Quantum Diaries: “Chamonix 2012″ High Hopes 

    kb
    Ken Bloom

    “At the start of each calendar year, the CERN management holds a workshop in Chamonix to discuss the LHC run plan for the coming year and beyond. This year’s meeting was held two weeks ago, and this past week CERN announced the outcomes. Now, after last year’s Chamonix, the plan came out differently than many of us had been expecting. But this year’s workshop results were consistent with this year’s rumors.

    There is a clear physics goal for this year: both CMS and ATLAS should each individually be in a position to discover the standard-model Higgs boson, if it exists. There are two ways that the LHC will try to make this possible. The first is to deliver as many collisions (i.e. as much integrated luminosity) as the LHC can manage. The integrated luminosity target for this year is fifteen inverse femtobarns for each experiment, three times as much as was delivered last year. It will still be a challenge to discover the Higgs with that much data; the experiments will have to run efficiently and the experiments will have to be as clever as ever. But it is possible. CERN is also prepared to extend the LHC run if necessary to meet this luminosity target. This is important, as the LHC will enter a long shutdown after 2012, so this year is our last shot for a while at making a discovery, of a Higgs or anything else. We should remember that last year’s target was a mere one inverse femtobarn, yet we got five times that. Can we hope that the LHC will outperform expectations again this year?”

    higgs
    One possible signature of a Higgs boson from a simulated proton-proton collision. It decays almost immediately into two jets of hadrons and two electrons, visible as lines. (Wikipedia)

    See Ken’s full post here.

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  • richardmitnick 6:45 am on February 17, 2012 Permalink | Reply
    Tags: ATLAS, ATLAS Blog, , , , , ,   

    From the ATLAS Blog – Vivek Jain “From 0-60 in 10 million seconds! – Part 1″ 


    ATLAS

    Read Vivek Jain on “…how the data that we collect gets turned into a published result….”

    vj
    Vivek Jain

    i1
    Signals left behind by different particle species

    See the blog post here.

     
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