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Figure 3.1: A “Livingston plot” illustrating the development of accelerator technology[9].17
8.3 T. Such high fields were not achievable in the previous generation of acceleratormagnets primarily due to the critical current density at their operating temperatureof 4.8 K. An improvement is effected in the LHC dipoles by using superfluid heliumat a temperature of 1.9 K for cooling.3.1.1 Layout and ParametersThe general geometry of the LHC lattice is imposed by the characteristics of the preexistingLEP tunnel that houses it. The total layout is split into eight arcs interrupted byso called “long straight sections” (LSS). Each of these LSS is located at an access pointto the tunnel. While there is only a single accelerator ring, the two beams are kept inseparate vacuum pipes, with crossings occurring at four insertion regions (IR) wherethe experiments are located: ATLAS at IR1, ALICE at IR2, CMS at IR5 and LHCbat IR8. IR4 houses the RF acceleration and feedback systems for the beams. IR3houses the momentum cleaning assembly, which strips off leading or trailing particlesthat do not fit the acceleration envelope provided by the RF system. IR7 contains thebetatron cleaning system, which removes particles with large transverse oscillationsfrom the beam [11].Injector ChainThe LHC is only the final stage of a chain of proton accelerators at CERN. Initially,hydrogen gas is ionized and the protons are accelerated to about 75 keV in a duoplasmatronion source. A linear RFQ accelerator, LINAC2, then accelerates them to about50 MeV. Further acceleration stages proceed through three synchrotrons, the ProtonSynchrotron Booster (PSB, up to 1.4 GeV), the Proton Synchrotron (PS, 25 GeV) andthe Super Proton Synchrotron (SPS, 450 GeV).Lead ions for heavy ion operation are produced in the Electron Cyclotron Resonance(ECR) ion source, where they are stripped down to a Pb 27+ state on average. Then,a separate linear accelerator (LINAC3) accelerates them up to an energy of about4.2 MeV per nucleon before they pass through a carbon foil stripper that increasestheir ionization state to Pb 54+ into LEIR, the Low Energy Ion Ring. Because thenumber of ions produced per source pulse is low, multiple pulses are stacked andconditioned in LEIR. After acceleration up to 72 MeV/n, they pass into the PS andare accelerated to an energy of 1.4 GeV/n. They pass afterwards to the SPS througha second-stage stripper that produces a fully ionized Pb 82+ state and are acceleratedup to 177 GeV/n before passing into the LHC proper.Due to the needs of RF acceleration and experiment timing, the particles in theLHC travel in bunches. The fundamental LHC clock has a rate of 40 MHz, whichprovides a natural value for the bunch separation time of 25 ns. This creates spacefor 3564 bunches on each beam, but practically envisioned operation schemes needto respect further operational constraints such as the switching times of the variousinjection kicker magnets along the way. The expected bunch dispositions for nominaloperation with protons and heavy ions are depicted in Fig. 3.2 and Fig. 3.3, yielding18
Page 5 and 6: 3.2.10 CMS Online Software . . . .
Page 7 and 8: factor. The selected events are the
Page 9: Figure 2.1: Expected dijet mass spe
Page 12 and 13: Figure 2.3: Left: Dilepton mass dis
Page 14 and 15: W −Z, γZ, γZ, γW +Z, γFigure
Page 16 and 17: ggHVHg(a)g(b)q¯q¯qHHV ∗q(c)qq(d
Page 18: Events per 4 GeV bin450400350300250
Page 21: 3 Experimental Setup3.1 Large Hadro
Page 26 and 27: luminosity) and limited storage ban
Page 28 and 29: Figure 3.4: Layout of the CMS pixel
Page 30 and 31: Figure 3.6: Transverse section illu
Page 32 and 33: Figure 3.8: HCAL jet energy resolut
Page 34 and 35: staggered by a half-cell each. A dr
Page 36 and 37: acceptance signal is distributed to
Page 38 and 39: Figure 3.11: Generic state machine
Page 40 and 41: Figure 3.12: Components of a CMSSW
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Page 44 and 45: In addition, the GCT calculates a n
Page 46 and 47: Figure 4.4: η boundary between the
Page 48 and 49: Figure 4.5: Organization of the DTT
Page 50 and 51: Condition Type Subtype Parametersmu
Page 52 and 53: oards making up the GT and sends th
Page 54 and 55: • ESProducers: components that re
Page 56 and 57: 5 Pattern Testing for the Level-1 G
Page 58 and 59: the required processing is mostly c
Page 60 and 61: RAW DIGIL1GctJetCandCollection (for
Page 62 and 63: information about an event that is
Page 64 and 65: muons 2 or two PSB channels (named
Page 66 and 67: 5.3 Software ImplementationThe exec
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Test Execution PanelThe test execut
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Figure 5.10: The pattern test resul
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FEDRawDataCollectionL1GlobalTrigger
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Figure 6.3: Result of a Function Te
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Figure 6.6: Disagreements in e/γ a
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Figure 6.9: TestCell output from an
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Bibliography[1] Abraham Pais. Inwar
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