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A comprehensive study of perturbative and non-perturbative quantum chromodynamics in measurements of the underlying even...

Permanent Link: http://ufdc.ufl.edu/UFE0041617/00001

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Title: A comprehensive study of perturbative and non-perturbative quantum chromodynamics in measurements of the underlying event and the transverse momentum of the Z boson with the CMS detector at the LHC
Physical Description: 1 online resource (130 p.)
Language: english
Creator: Kotov, Khristian
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: cms, compact, hep, high, large, lhc, qcd, quantum
Physics -- Dissertations, Academic -- UF
Genre: Physics thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: We explore the potential for an early measurement of the Z boson transverse momentum distribution in the muon decay channel for the first 10-100 1/pb of the LHC data at 10 TeV collision energy. In this simulation study, we exercise data driven techniques and study efficiency of the event selection and the muon pT resolution as it can be done for the first data. The theory and experimental uncertainties are estimated < 10% in the low-qT region and a few % for the high-qT region. Also we present a first measurement of the multiplicity and transverse momentum flow in the first LHC collision data at 900 GeV center-of-mass energy recorded in December 2009. The systematic bias to the measurement due to the event selection and track reconstruction are estimated using the full CMS simulation. The results are compared to the predictions of one of the soft QCD models, previously studied by CDF collaboration at the Tevatron.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Khristian Kotov.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Acosta, Darin E.
Local: Co-adviser: Mitselmakher, Gena.

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Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041617:00001

Permanent Link: http://ufdc.ufl.edu/UFE0041617/00001

Material Information

Title: A comprehensive study of perturbative and non-perturbative quantum chromodynamics in measurements of the underlying event and the transverse momentum of the Z boson with the CMS detector at the LHC
Physical Description: 1 online resource (130 p.)
Language: english
Creator: Kotov, Khristian
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: cms, compact, hep, high, large, lhc, qcd, quantum
Physics -- Dissertations, Academic -- UF
Genre: Physics thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: We explore the potential for an early measurement of the Z boson transverse momentum distribution in the muon decay channel for the first 10-100 1/pb of the LHC data at 10 TeV collision energy. In this simulation study, we exercise data driven techniques and study efficiency of the event selection and the muon pT resolution as it can be done for the first data. The theory and experimental uncertainties are estimated < 10% in the low-qT region and a few % for the high-qT region. Also we present a first measurement of the multiplicity and transverse momentum flow in the first LHC collision data at 900 GeV center-of-mass energy recorded in December 2009. The systematic bias to the measurement due to the event selection and track reconstruction are estimated using the full CMS simulation. The results are compared to the predictions of one of the soft QCD models, previously studied by CDF collaboration at the Tevatron.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Khristian Kotov.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Acosta, Darin E.
Local: Co-adviser: Mitselmakher, Gena.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041617:00001


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ThisrstchapterofthedissertationIwritethelast.ItistheonlychapterwhereIfeelfreetostepasideoftheformalrulesofwritingascienticdocumentanduseaneverydaylanguagetoacknowledgeallthepeople,whostayunidentiedbehindtheimpersonalweintherestofthisdocument.Ialsowanttorememberandthankmanyotherswhoinuencedmyprofessionalandpersonallifeintimeperiodofthegraduateschool,whichIamnowcompletingwiththisdocument.IconsidermyselfluckytoworkwithprofessorDarinAcosta,myscienticadviserintheUFgraduateschool.HishardworkandgreattalentmadehimoneofthetoprankingguresintheCMScollaboration.Andyet,despitethebusynesshendstimeforaregularstudentlikeme.Heservedmeanexampleofhowtobeaneffectivepartofabigcollaboration.IwanttothankprofessorGuenakhMitselmakherfortheinspiration,whichhealwaysgivesme.Hisoutstandingcharisma,greattalenttondtherightwords,andpositiveattitudeservedmeabrilliantexampleofqualitiesneededtobuildastrongteam.IamverythankfultoprofessorAndreyKorytov,whobroughtmetoCSCDataQualityMonitoringprojectandintroducedmetotheCMSmuonendcapcommunity.Hisremarkablepatienceandwillingnesstoexplaindifferentmattersinparticlephysicsmadehimagreatsourceofknowledgeformanystudentsinourgroup.IamgratefultoprofessorKonstantinMatchev,whocanseeandexplainthesimplephysicsbehindthecomplicatedequationsofthequantumeldtheory.Ivalueeveryminuteofthetime,thatIspentinhisofce.IamreallygladthatImetprofessorIvanFuric,whogavemenumerousvaluablepiecesofadvice,concerningmyanalyses.Iamgratefulformanyusefuldiscussions,whichhappenedinhisgroupamongme,MingshuiChen,JonatanPiedra,andNickKypreos. 3

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page ACKNOWLEDGMENTS .................................. 3 LISTOFTABLES ...................................... 8 LISTOFFIGURES ..................................... 10 ABSTRACT ......................................... 16 CHAPTER 1INTRODUCTION ................................... 17 2THESTANDARDMODEL .............................. 20 2.1FormalismoftheModel ............................ 20 2.2AsymptoticFreedomandColorConnementofStrongInteractions .... 23 2.3ElectroweakVectorBosonProduction .................... 24 2.4BeyondtheStandardModel .......................... 25 3THEACCELERATORCOMPLEXANDCOLLIDERPHENOMENOLOGY ... 27 3.1TheLHCAcceleratorComplex ........................ 27 3.2PhenomenologyoftheProton-ProtonColliders ............... 30 4THECOMPACTMUONSOLENOIDDETECTOREXPERIMENT ........ 33 4.1MuonSystem .................................. 34 4.2Magnet ..................................... 37 4.3HadronCalorimeter .............................. 38 4.4ElectromagneticCalorimeter ......................... 38 4.5InnerTrackingSystem ............................. 41 4.6TriggerSystem ................................. 41 5THECSCLEVEL-1TRIGGER ........................... 44 5.1CSCTriggerElectronics ............................ 44 5.2CSCTrack-FindingLogic ........................... 46 5.3HardwareTestsandCommissioningoftheCSCTrack-Finder ....... 48 5.3.1BasicBenchTests ........................... 48 5.3.2HardwareTestsusingCosmicRayMuons .............. 49 5.3.3BeamTestsof2003 .......................... 49 5.3.4BeamTestsof2004 .......................... 52 5.3.5SliceTestsof2005 ........................... 53 5.3.6MagnetTestandCosmicChallengeof2006 ............. 54 5.3.7Commissioningin2007 ..................... 56 5.3.8CosmicRunAtFourTeslaof2008 .................. 58 5

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................. 58 5.4.1EfciencyoftheLevel-1CSCTrigger ................. 59 5.4.2EfciencyoftheTrack-FindinginLevel-1CSCTrigger ....... 62 6SIMULATION ..................................... 65 6.1EventGeneration ................................ 65 6.2DetectorSimulationandReconstruction ................... 66 7THESHAPEOFTHEZBOSONTRANSVERSEMOMENTUMDISTRIBUTIONINMUONDECAYCHANNEL ............................ 67 7.1Theory ...................................... 67 7.2TheqTSpectrumShape ............................ 70 7.2.1SoftPartoftheqTSpectrum ..................... 71 7.2.2HardPartoftheqTSpectrum ..................... 72 7.3Analysis ..................................... 72 7.3.1EventSelectionandBackgrounds ................... 73 7.3.1.1Trigger ............................ 74 7.3.1.2Ofineeventselection .................... 74 7.3.2Efciencies ............................... 77 7.3.2.1Matchingalgorithm ..................... 78 7.3.2.2Sidebandsubtraction .................... 78 7.3.2.3Triggerefciency ....................... 80 7.3.2.4Muonreconstructionefciency ............... 81 7.3.2.52-dimensionalefciency ................... 83 7.3.2.6Di-muonefciency ...................... 84 7.3.2.7Efciencyoftheisolationcut ................ 85 7.3.3FiniteResolution ............................ 90 7.3.3.1MeasuringthemuonpTresolutionfromdata ....... 91 7.3.3.2ImpactoftheresolutiononthemeasuredqTmethod .. 95 7.3.4Uncertainties .............................. 96 7.3.4.1Theory ............................ 96 7.3.4.2Experiment .......................... 98 7.4Summary .................................... 101 8AMEASUREMENTOFTHEMULTIPLICITYANDTRANSVERSEMOMENTUMSPECTRAOFCHARGEDTRACKSUSINGTHEFIRSTLHCCOLLISIONDATA ......................................... 103 8.1PhenomenologyofHadronCollisions .................... 103 8.2MethodsforStudyingtheSoftQCDPhysics ................. 105 8.2.1Data ................................... 105 8.2.2Observables ............................... 106 8.3Analysis ..................................... 107 8.3.1DataSelection ............................. 108 8.3.2Trigger-basedeventselection ..................... 109 6

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............... 110 8.3.3TrackSelection ............................. 111 8.3.4DetectorPerformance ......................... 113 8.3.4.1Trigger ............................ 114 8.3.4.2Tracker ............................ 116 8.3.5FinalResults .............................. 116 8.4Summary .................................... 120 APPENDIX APERFORMANCEOFTHEDRELL-YANEVENTSELECTIONAT14TEVLHCCOLLISIONENERGY ................................ 121 BEFFICIENCYOFTHEKINEMATICSCUTSTOTHEDRELL-YANEVENTS .. 123 CPERFORMANCEOFTHEDRELL-YANINVARIANTMASSFITS ........ 125 REFERENCES ....................................... 127 BIOGRAPHICALSKETCH ................................ 130 7

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Table page 2-1StandardModelfermions. .............................. 21 2-2StandardModelbosons. ............................... 23 3-1SomeoftheLHCcharacteristics. .......................... 29 3-2Theobservables,whicharecommonlyusedinthehadroncolliderphysics. .. 32 7-1BinningoftheqTspectrum.LastcolumnestimatesnumberofDrell-YaneventsfromZpeakwithbothmuonswithinthesinglemuontriggeracceptance(jj<2.1)for10pb1atp ... 73 7-2Triggerpathsusedforthe10TeVscenario(L=1031cm2s1).Neitherpathisprescaled. ....................................... 74 7-3Thenumberofeventsaftereachselectionstep.TheLOcrosssectionoftheW+jetsandttprocessesscalesdownto70%at10TeVcollisionenergycomparedto14TeV.FortheZ!backgroundprocess(lastrow)thegeneratorlevelcutontheinvariantmassofwassetat40GeV/c2for14TeVscenarioandat20GeV/c2for10TeV(thesetwocutschangethecrosssectionroughlybyafactorof2atthesameenergy).TheQCDbackgroundishigherforthe10TeVscenariobecauseHigh-Leveltriggersapplylooserimpactparametercut(dxy<2cmasopposedtodxy<0.02cmfor14TeV). ........... 75 7-4Theperformanceofthecutontheinvariantmassandthetracker-basedmuonisolation. ....................................... 76 7-5Thewidthofasinglegaussian,ttingthepTptrueT .. 90 7-6Theresolutionparametersofthedoublegaussiant. .............. 91 7-7Theresolutionparameter,,extractedfromthetoftheZresonanceinseveralranges.Theuncertaintyforthestart-upscenario(only10pb1ofdata)istakendirectlyfromthet.Forthegenerator-leveldataandfortheidealalignmentscenarioweestimatetheuncertaintyasthestandarddeviationofthe,evaluatedonseveralsubsetsoftheinitialdatasample. ................... 93 8-1Datafortheanalysis ................................. 108 8-2Totalnumberofeventsafterapplyingvarioustrigger-basedselectioncriteria. 110 8-3Averagez-coordinateofthevertex. ......................... 111 8

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..................................... 121 A-2Numberofeventsaftereachselectionstep.Lastcolumnrepresentsthenumberofevents,weightedfor10pb1ofdata. ...................... 121 A-3Performanceoflast2selectionsteps:cutontheinvariantmassandthemuonisolation. ....................................... 122 9

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Figure page 3-1TheLargeHadronCollider. ............................. 28 3-2AsinglecelloftheLargeHadronCollider. ..................... 28 3-3ExperimentsontheLargeHadronCollider. .................... 30 3-4TheCTEQ[ 51 ]partondistributionfunctionsatQ=2and100GeV/c. ..... 31 4-1GeneralviewoftheCMSdetector. ......................... 33 4-2MuonsystemoftheCMS. .............................. 35 4-3Twelvesectorsofbarrelmuonsystem. ....................... 35 4-4Adrifttubechamber(left)andasingledrifttubecell(right). ........... 36 4-5Endcapmuonchambersmountedontheirondisks. ............... 36 4-6Sketch(left)andmechanicaldesign(right)ofacathodestripchamber. ..... 37 4-7QuarterviewoftheHCALdetectors. ........................ 39 4-8Thejettransverseenergyresolutionasafunctionofthesimulatedjettransverseenergyforbarreljets(jj<1.4),endcapjets(1.4
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................. 54 5-8Timeofreceivingtriggerprimitives(LCTsandDTstubs)fromtriggersector#4intheCSCTrack-FindercraterelatedtothetimeofLCTs,receivedfromasinglereferencechamberinthissector. ...................... 56 5-9TheCSCTrack-FindercrateintheUSCundergroundcavern. .......... 57 5-10Thetimedifference(inbunchcrossings)betweenLCTsinthetoppartofoneendcapandthebottompartofanotherendcap.Effectively,thisisthetime-of-ightbetweenthetwoendcapsasseenbytheCSCTrack-Finder. .......... 60 5-11Theoftrackertrack(ontheleft)andtriggerprimitive(ontheright). ...... 62 5-12Differencebetween(ontheleft)and(ontheright)coordinatesofthetriggerprimitiveandtrackertrack. .............................. 63 5-13EfciencyofCSCLevel-1triggerasafunctionofofinereconstructedpTinthetracker.Ontheleft:efciencyforbottomCSCsectors,ontheright:topCSCsectors. ..................................... 63 5-14EfciencyofCSCTFtobuildamuoncandidatefromseveraltracksegmentsseparatedinbinsofaqualitytagassignedbytheCSCTFalgorithms. ..... 64 7-1Feynmandiagramsforzerothorder(left),next-to-leadingorder(middle),andsomediagramsfornext-to-next-to-leadingorder(right)Drell-Yanproduction. 68 7-2qTspectrumofDrell-Yanprocess(blacksolidline)andsuperimposedqTspectraofZ0(reddashedline)andW0(bluedottedline)decaysofmassof1000GeV/c2each.ThesespectraserveonlyfordemonstrationpurposesandneitherZ0orW0massnorcrosssectionoftheirproductionhaverelationtoanyspecictheorymodel. ..................................... 69 7-3ShapeoftransversemomentumdistributionofZbosongeneratedbyPythiainproton-protoncollisionsatp ....... 70 7-4RatioofqTspectrafor4standardPythia'sUnderlyingEventtunes. ....... 71 7-5Hardpart(qT>30GeV/c)ofthenormalizedqTspectruminlinearscale(left)andinlogscale(right).GreendotsPythiaresults,redtop-pointingtrianglesNNLOFEWZzresults(CTEQ6.6),bluebottom-pointingtrianglesNLOFEWZzresults(CTEQ6.6),cyanstarsMC@NLOresults. .......... 72 7-6TheqTdistributionforthesignalandtheleadingbackgrounds(stacked)in10TeVsampleafterapplyingtheselectioncuts. ................. 77 11

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....................... 79 7-8EfciencyofthesinglemuontriggersasfunctionsofpT(leftplots)and(rightplots).TherstrowcorrespondstoLevel-1trigger,secondLevel-2,andthirdLevel-3.MonteCarlobluedots,tag-and-probewithsidebandsub-tractionredtriangles.Theresultsareobtainedon25pb1ofDrell-Yanproduction. ...................................... 82 7-9EfciencyofmuonreconstructionasafunctionofpT(leftplots)and(rightplots).Therstrowcorrespondstostandalonemuonreconstruction.Secondefciencyofsilicontrackertoreconstructmuontrack.MonteCarloisinblue,tag-and-probewithsidebandsubtractionred. .............. 83 7-10MonteCarloefciencytotriggerthedi-muonevent,whichpassesthekinematiccutsusingthesinglemuontrigger. ......................... 86 7-11TheMonteCarloefciencytoreconstruct2trackermuons,whichpassthekinematiccutandtriggerthesinglemuontrigger. ................. 86 7-12Thedata-drivenefciencymeasurementofthestandardtracker-basedisolationcutonasinglesignalmuon. ............................. 88 7-13DensityofchargedparticlesasafunctionofthepTofthemuonpair. ...... 88 7-14Ontheleft:MonteCarloisolationefciencyforthehighest(redtop-pointingtriangles)andthelow(bluebottom-pointingtriangles)pTmuonsfromthepair.Greendotsthedata-drivenmeasurement.Ontheright:proleofangleinXYplanebetween~pTofZand~pTvectorsofthemuons(highestpTred,lowpTblue)fromthepair.Horizontalline=separatesforwardandbackwardhemispheresalongthedirectionof~pTofZ. ............ 89 7-15Redtop-pointingtrianglesefciencyofanymuonfromthedi-muoneventtopasstheisolationcut.Bluebottom-pointingtrianglesefciencyofbothmuonsfromthepairtopasstheisolationcut. ................... 89 7-16DistributionofpTptrueT ........................... 91 12

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........................ 92 7-18FitoftheZresonance.250pb1areusedinthedistributionsforthegeneratorandforthefullsimulationwiththeidealalignment.Forthestart-upscenarioweuse10pb1ofDrell-Yanproduction. ..................... 93 7-19RatiooftheqTspectrumshapeonthelevelofgeneratortotheqTspectrumshapeafterfullCMSsimulation.Theplotisproducedon1fb1ofdata(100pb1misalignmentscenario). ............................... 95 7-20Theunfoldingcorrectionsforthestart-upalignmentscenario(left)andfortheidealalignmentscenario(right).ToprowqT<30GeV/c,bottomrowqT<200GeV/c.Thesystematicuncertainty(shadedarea)forthecorrectionfactorsisdiscussedindetailinsection 7.3.4.2 ontheexperimentalsystematicuncertainties. .................................... 97 7-21Ontheleft:normalizeddifferentiald=dqTNLOcrosssectionwitherrorsduetofactorizationandrenormalization.Ontheright:absolutescaleoftheuncertaintyonthedifferentialNLOcrosssectionasafunctionofqT 98 7-22PDFuncertaintiesinthecrosssection.CTEQ6.1bluetop-pointingtriangles,MRST2006nnloredbottom-pointingtriangles.Ontheleft:differentialcrosssectionuncertaintiesinseveralqTbins.Ontheright:uncertaintyonratioofdifferentialcrosssectionineachqTbintototalcrosssectionoftheprocess. .. 99 7-23Bluebottom-pointingtrianglestagandprobewithoutthesidebandsubtraction,redtop-pointingtrianglesstandardtagandprobewiththesidebandsubtractiontechnique. ...................................... 100 7-24Bin-by-bincorrectionfactorsforthestart-upalignmentscenario(leftplot)andfortheidealalignmentscenario(rightplot).Forthestart-upalignmentthetrianglepointersofthegrapharetheaveragebetweenmaximumandminimumcorrections,calculatedwiththetwomodelsofsmearingthemuonpT(theverticalerrorbarsconnecttheresultsofthetwomodels).TrianglepointersontherightplotcorrespondtothemuonpTresolutioninidealalignmentscenario.ThetwoothermodelsofsmearingthemuonpTareconnectedbytheverticalbars. .. 101 13

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...................... 102 8-1Regionsforthedataselection. ........................... 106 8-2Thedensityofchargedparticles(left)andtransversemomentumow(right)observablesformin-biasevents.TheplotsaregeneratedwiththeD6Ttune[ 39 ]forPythia. .................................... 107 8-3Distributionofthez-coordinateforthevertexinrun#124230. .......... 111 8-4Distributionofthetransversemomentumbefore(left)andafter(right)thecutontheuncertaintyofthetransversemomentummeasurement.ThecuthelpstocleanthesamplefromtrackwithunreliablepTmeasurement(especiallyinthehigh-pTtail)andachievebetteragreementbetweenthedataandD6TPythiasimulation. .................................. 113 8-5MonteCarloefciencyofthetrackselectioncutstoprimaryparticles(left)andsecondaryparticles(right).TheplotiskindlyofferedbyGiuseppeCerati. 113 8-6EfciencyoftheBSCtriggerselectioninsimulation(threePythiatunesareshown)andindata. ................................. 114 8-7Topplots:dN dd(left)anddPsumT ..................................... 115 8-8Validationoftheinnertrackersimulation.Inpanels:Anumberofdegreesoffreedomofthetrackt;Bnormalizedtrackt2;C,D,Ftrack'spseudorapidity,azimuthalangle,andtransversemomentum,respectively;Epereventtrackmultiplicity.Linessimulation,dotsdata. ................... 117 8-9Chargedparticledensity(left)andtransversemomentumow(right).Datadots,MonteCarlocircles.Toprowtowardregion,middlerowtransverseregion,bottomrowawayregion.Intheplotsforthetransverseregionwealsoshowsystematicuncertainty(shadedarea). ................. 118 14

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........................ 123 B-2Topleft:scatterplotofpTofmuonversuspTofmuonpairforhigherpTmuonfromthepair.Topright:sameforlowpTmuonfromthepair.Bottom:efciencyofhigherpTmuon(redtop-pointingtriangles)andlowpTmuon(bluebottom-pointingtriangles)injj<2.1region,topasspT>20GeV/ccut(horizontallineontopplots).EfciencycurvetopassthecutbybothmuonssimultaneouslypreciselyfollowsthebluecurveforthelowpTmuonand,therefore,itisnotdisplayed. ....................................... 124 C-1TheresultsoftheZpeakt.Leftcolumncorrespondstothettingrangeminv2(76)GeV/c2,middlecolumnisfor(80)GeV/c2range,andrightcolumnisfor(84)GeV/c2.Firstrowshowsttingcurvesforthegenerator-leveldistributionoftheminv,secondrowisforminvsimulatedwiththeidealalignmentscenario,thirdrowisforthestartupscenario.Thethickredcurveisthevoigtiancontribution,thebluecurveisasumoftheinterferenceterm(greenthincurvebelowzero)andgammaterm(brownthinmonotonouscurveabovezero). .. 126 15

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1 ]atCERN(EuropeanOrganizationforNuclearResearch)isexpectedtodeliverproton-protoncollisionsupto14TeVcenter-of-massenergyandnuclei-nucleicollisionsuptoa2.76TeV/nucleonenergy,yieldingatotalcenterofmassenergyofupto1.15PeV.Ithosts2general-purposedetectors:AToroidalLhcApparatuS(ATLAS)andCompactMuonSolenoid(CMS),aswellasLargeHadronColliderbeauty(LHCb)b-physicsexperiment,ALargeIonColliderExperiment(ALICE),andtworelativelysmallspecial-purposedetectors:TotalCrossSection,ElasticScatteringandDiffractionDissociation(TOTEM)andLargeHadronColliderforward(LHCf).ThisthesissummarizesresearchperformedintheCMSdetectorcollaboration.Theauthorparticipatedinthestartofthisnewexperimentaninfrequenteventintheeld.Thetechnicalexperienceaccumulatedovertheyearsoftheassemblingandcommissioningofthedetectorlaysthegroundfortherstpartofthethesis.ItcoverscommissioningofthetriggersystemfortheCathodeStripChambersgaseousdetectorsintheCMSendcapdisks,whichregisterschargedparticleswithhighresolutioninspaceandtime.Thesecondpartofthethesiscontainstwophysicsanalyses.TherstanalysisexploresthepotentialfortheearlymeasurementoftheshapeoftheZbosontransversemomentumspectrum.Theshapeofthespectruminthelowtransversemomentumregion(.10GeV/c)canbeusedtovalidatethephenomenologicalmodelsofthenon-perturbativestronginteractions.Theshapeofthespectruminthehightransversemomentumregion(&30GeV/c)iswellpredicted 18

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2 ].By1968itwassuccessfullyextendedtoincludetheweakforce[ 3 5 ].Theelectroweakunicationtheorypredictedtheexistenceofnewheavybosons:W+,W,andZ.ThechargedWbosonperfectlytsthe-decayphenomenon(transitionofafreeneutronintoaprotonwiththeemittanceofanelectronandneutrino).TheZbosonwasrstdetectedastheneutralcurrentintheGargamellebubblechamberexperimentin1973[ 6 ].TenyearslatertheZbosonwasexplicitlyobservedintheUA1[ 7 ]andUA2[ 8 ]experimentsontheSuperProtonSynchrotroncolliderattheCERNlaboratory.Thetheoryofstrongforcesstartedwiththenumerousattemptstoclassifytheknownhadrons.Intheearly1960sasuccessfulclassicationassumingtheexistenceofthreeavoursofnewparticlesinsidethehadronswasproposed[ 9 ].Itwasalsorecognizedthatanadditionalnewquantumnumberneedstobeassignedtotheseparticlesinordertoexplainexperimentalobservation.Theseparticleswereobservedinaseriesofelectron-protonscatteringexperimentsperformedfrom1967through1973attheStanfordLinearAcceleratorCenter(SLAC)[ 10 ].Thenewparticles(knownasquarksandgluons)withthenewquantumnumber(knownascolor)setthegroundforthetheoryofstrongforces(QuantumchromodynamicsorQCD)[ 11 ].Thetheoryculminatedin1974inpredictingthepropertiesoftheboundstateofcquarks-antiquarkpair,whichwasdiscoveredthereafter[ 12 13 ].ThemixtureofelectroweaktheoryandQCDsetsthebasisoftheStandardModel,asweknowittoday. 20

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2-1 .Eachgenerationconsistsof2quarks,1chargedlepton,and1neutrino.Therstgenerationisthesetoflightestparticles,allofwhicharealsostable.Thesecondgenerationismadeoftheheavieranalogsofparticlesfromtherstgeneration.Themuonneutrino()istheonlystableparticleofthesecondgeneration.Thesamepatternrepeatsitselfinthethirdgeneration,whichconsistsoftheheaviestunstableparticles(exceptforthetauneutrino,whichisstable). Table2-1. StandardModelfermions. electriccharge 1stgeneration 2ndgeneration 3rdgeneration Quarks +2/3 -1/3 Leptons -1 0 TheStandardModelisformulatedintermsofthegaugeeldLagrangianbeinginvariantundertransformationoftheSU(3)CSU(2)LU(1)Ysymmetrygroup.Thechoiceofthesymmetrygroupisdictatedbyaseriesofexperimentalobservations,whichcantintothetheoryofthisminimalsymmetry. 21

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4GaGaHere,theqisanSU(3)Cquarkcoloreld.TheinteractionsaremediatedbythegluonvectoreldGaandtheGarepresentsthegaugeinvariantgluoneldstrengthtensor.Thesecondtermdescribestheelectroweakinteractions:Lelectroweak=Li@ig 4WW1 4BBThetheorypostulatestwodifferentformsofinteractionsforfermionswithpositiveandnegativehelicity.1Thisisaconsequenceofexperimentalobservations,whichshowthatallproducedandobservedneutrinoshavenegativehelicity.Negativeandpositivehelicityisalsoreferredtoasleft-andright-handedness.Theleft-handedfermions,L,arearrangedinSU(2)isospindoublets(e.g.left-handedelectronandelectronneutrino).Theright-handedfermions,R,areSU(2)singlets(e.g.right-handedmuon).TheWandBarethe3-vectormasslessgaugebosonswithtwodifferentcouplingstrengthsgandg0.ThelasttermintroducesoneextrascalargaugeeldtothetheorytheHiggseld:ItallowssomeofinitiallymasslessgaugebosonstoacquiretheirmassesthroughthecouplingtothevacuumexpectationfortheHiggseld.ThevacuumexpectationfortheHiggseldisintroducedbythechoiceofV()potential,whichgeneratesthespontaneouselectroweaksymmetrybreaking.Thedetailsofthismechanismcanbefoundelsewhere[ 14 ].AllthebosonsarecataloguedinTable 2-2 .TheHiggsboson 22

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Table2-2. StandardModelbosons. Boson charge mass spin 0 1 0 0 1 91.18760.0021GeV/c2 80.3980.025GeV/c2 unknown 0 10 ]. 23

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15 ].Possiblenewheavygaugebosons(e.g.Z0[ 16 ]orW0[ 17 ])canmanifestthemselvesinthedi-leptoninvariantmassandtransversemomentumdistributionsoftheZboson. 18 ])cannotbeexplained.Thisisrefereedtoasthehierarchyproblem. 19 ]),isbasedontheassumptionofasymmetrybetweenfermionsandbosons.Itcansolvethehierarchy 25

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20 ],assumesthatextradimensioniscurledupinacircleofverysmallradius.Asaresultofphasecontinuityrequirementthistheorygeneratesinnitelyrepeatingmassspectraofparticles(referredtoasKaluza-Kleintowers).Themodelsofnewphysicsalsoprovidenewstableheavyparticles.Thosecanbeusedascandidatesfordarkmattertheunobservablepartofouruniverse,requiredbycosmologicalmeasurements. 26

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1 ]beforetheyenterthemainLHCring:a26657meterscircumferencesynchrotron(seeFigure 3-1 ).Thecomplexcanoperatewitheitherprotonbeamsorleadionbeams.Theparticlesareextractedfromhydrogen(protons)andfromleadplasma(ions).Theyarefedintothelinearaccelerators(LINACs)wheretheyareacceleratedtotheenergyof50MeVforprotons(inLINAC2)and4.2MeVpernucleonforions(inLINAC3).InthenextstepprotonsentertheProtonSynchrotronBooster(PSB)wheretheyreachenergyof1.4GeV.IonsentertheLowEnergyIonRing(LEIR)wheretheyareacceleratedto72MeVenergypernucleon.BothtypesofacceleratingparticlescontinuetheirwayintotheProtonSynchrotron(PS)acceleratorwhereprotonsreachanenergyof26GeVandionsreachanenergyof5.9GeVpernucleon.FromthePSmachineparticlesmoveintotheSuperProtonSynchrotron(SPS)machine.Beingacceleratedto450GeV(protons)and177GeVpernucleon(ions)theyarenallyinjectedintothemainLHCring.ThemainLHCringrampstheprotonsuptoamaximumof7TeV(nominalenergyinthedesign).ThemainLHCringconsistsofmultipleLHCcells(110meach).OneLHCcellisasetoflongdipole8.33Tmagnets1alternatingwithsmalldecapoleandsextupolecorrectormagnets.Themultipole-correctormagnetsareusedtocompensatetheeldimperfectionsinthedipolemagnetsandstabilizetrajectoriesforparticlesatlargeramplitudes(seeFigure 3-2 ).Quadrupolefocusinganddefocusingmagnetsprovidethestrongoverallfocusingeffecttothebeam.Thetwomajorparameters,characterizingtheperformanceofthecollider,arethebeamenergy(E)andthecolliderluminosity(L).Thebeamenergyisanaverageenergy 27

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TheLargeHadronCollider. AsinglecelloftheLargeHadronCollider. ofprotonsineachbeam.TheLHCachieved1.18TeVbeamenergyatthestart-upin2009andhasreached3.5TeVbeamenergyinMarch2010.Theluminositymeasures 28

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3-1 showstheachievedandexpectedperformanceoftheLHCaccelerator. Table3-1. SomeoftheLHCcharacteristics. Parameter 2009 Plansfor2010 Design Injectionenergy 450GeV Collisionenergy 0.9.36TeV 7TeV 14TeV Numberofbunchesperbeam 1 43,156,144,288... 2808 Bunchstructure 24.95ns=40.08MHz Numberofprotonsperbunch 2109 3-3 .Thetwohighluminositycollisionpointshosttwogeneralpurposedetectors:CMSandATLAS.Twootherpointshostdetectorsfortheb-physics(LHCb)andfortheheavyionphysics(ALICE). 29

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ExperimentsontheLargeHadronCollider. 30

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3-4 showsanexampleofthePDFs. TheCTEQ[ 51 ]partondistributionfunctionsatQ=2and100GeV/c. Someoftheprotonremnants,whichdonotparticipateinthehardscattering,deectfromthebeamaxisatsmallangles.Movingalongtheirtrajectoriestheyenterthebeampipeandescapedetection,carryingawayanunknownfractionofmomentum.Therefore,theexactxaandxblongitudinalmomentumfractionsinagivenpartonscatteringareintrinsicallyunknown.Onecanfactorouttheunknownboostalongthebeamaxisbyusingtheso-calledtransverseobservables.SomeofthesephysicsquantitiesareshowninTable 3-2 .Pseudorapidity,denedas=lntan( 2lnE+pz 31

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Theobservables,whicharecommonlyusedinthehadroncolliderphysics. Observable Denition Comment momentumperpendicular tothebeamdirection runsoverenergydeposits, leftbytheparticle) transverseenergy(relatedto theneutrino-likeparticles escapingthedetection) andthebeamaxis,becauseforhadroncolliderstheparticleproductionisconstantasafunctionofrapidity.Thetotalproton-protoncrosssectionat10TeVcenter-of-massbeamenergyisaround100mb(or1027cm2).Mostoftheeventsinhadroncollisionsaretheelasticandinelasticscatteringswithlowtransversemomentumtransfer(thelow-pTorsoftQCDprocesses).Phenomenologically,thelow-pTscalecomesouttobeanumberoftheorderof1.5.5GeV/c[ 21 ].Thehardscatteringorhigh-pTQCDprocessesyieldjetsspraysofparticleswithapproximatelycollinearinitialmomentum.ThesoftandhardQCDprocessesarethedominantprocessesonhadroncolliders.Theyarebackgroundformostotherphysicssearches. 32

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22 ]needstomeetnumeroustechnicalrequirements,setbyboththeLHCmachineandthephysicssearches.AtthedesignluminosityCMSwillobserveonaverage20inelasticcollisionsandaround1000chargedparticles(every25ns).Thedetectorresponsetotheproductsofinteractionunderstudywillbesuperimposedontheresponsetotheproductsofotherinteractionsinthesameandnearbybunchcrossings.Resolvingsuchresponsesrequiresahighgranularitydetectorwithalargenumberofwell-synchronizeddetectorelectronicchannels.Manyoftheanticipatednewphysicsprocessesinvolvehighmomentumparticles.Thestudyofsuchprocessesrequiresufcientlygoodmomentumresolution(pT=pT<10%atpT1TeV/c).Thisrequirementtranslatesintothehighmagneticeldinthetrackingvolumeofthedetectorandlongleverarmofthetrajectoryinthetrackingsystem.TheCMSisillustratedinFigure 4-1 .Thedetectorhasthebarrelpart,whichisclosedbythetwoendcapsoneachofitssides.TheoveralldimensionsoftheCMSarealengthof21.6m,adiameterof14.6m,andatotalweightof12500tons. GeneralviewoftheCMSdetector. 33

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4-2 )consistsofdetectorsofthreetypes:DriftTubes(DTs),CathodeStripChambers(CSCs),andResistivePlateChambers(RPCs).BarrelDTscoverthecentralregionofjj<1.2.CSCendcapscover0.9
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MuonsystemoftheCMS. layersofdriftcellsineachchamberarearrangedin3groupsof4consecutivelayersasitisshowninFigure 4-4 .The2groupsmeasurercoordinateastheyareparalleltothebeamand1groupmeasuresthez-coordinate. Twelvesectorsofbarrelmuonsystem. ThetwoendcapsoftheyokehousetheCSCsystem.ThechambersaremountedontheendcapirondisksasitisshowninFigure 4-5 .ThechambersarelabeledasMEf+,-g/station/ring/phi,where f+,-greferstotheendcap 35

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Adrifttubechamber(left)andasingledrifttubecell(right). Endcapmuonchambersmountedontheirondisks. EachCSCistrapezoidalinshapeandconsistsof6gasgapswithradially(fromthebeamaxis)alignedcathodestrips,andwiresapproximatelyalignedintheorthogonaldirection(Figure 4-6 ).Theanodewiresprovideaprecisetimingmeasurementofahit 36

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Sketch(left)andmechanicaldesign(right)ofacathodestripchamber. TheRPCsystemisintegratedintothebarrel(6stations)andendcaps(3stations).Itisusedmainlytoprovidefasttriggersignalsandunambiguouslyidentifytherelevantbunchcrossingsofthemuontracks,eveninpresenceofhighrateandbackgrounds.Thedouble-gapchamberswith2mmgapsizeoperatewithaC2H2F4basedgasmixtureat9kVelectricalpotentialdifference. 37

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4-7 .ThejetenergyresolutionoftheHCAL[ 37 ]forseveralrangesisshowninFigure 4-8 4-9 ).Thematerialofchoiceallowedthedesignofacompactcalorimeterinsidethesolenoidthatisfast(80%oflightisemittedwithin25ns),hasnegranularity(Moliereradiusis2.2cm),andisradiationresistant(upto10Mrad).Siliconavalanchephotodiodes(APDs)areusedasphotodetectorsinthebarrelandvacuumphototriodes(VPTs)intheendcaps. 38

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QuarterviewoftheHCALdetectors. Thejettransverseenergyresolutionasafunctionofthesimulatedjettransverseenergyforbarreljets(jj<1.4),endcapjets(1.4
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CutawayviewshowingECAL. whereSisthestochasticterm,Nthenoise,andCtheconstantterm.TheECALenergyresolutionisshowninFigure 4-10 ECALenergyresolution,(E)=E,asafunctionofelectronenergyasmeasuredfromabeamtest.Theenergywasmeasuredinanarrayof33crystalswithelectronsimpactingthecentralcrystal. 40

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4-11 )consistsoflayersofhybridpixeldetectorsandlayersofsiliconmicrostripdetectors.Thepixeldetectorsareclosesttotheinteractionvertex.Theyarearrangedinto3barrellayersand2diskspereachendcap.Thepixeldetectorscontain65millionpixels,100m150meach.Thesiliconmicrostripdetectorssurroundthepixeldetectors.TheyarearrangedintotheTrackerInnerBarrel(TIB)andTrackerOuterBarrel(TOB)layersandTrackerEndcap(TEC)disks.Thereare3additionalTrackerInnerendcapDisks(TID)insidetheTrackerOuterBarreloneachsideoftheTrackerInnerBarrel.Thesiliconmicrostriptrackercontains9.3millionstripswithapitchbetween80and180m. Quarterviewoftrackingsystemlayout. Thepixeltrackerhasspatialresolutionof10minrcoordinatesand20mforthezmeasurement.Thesiliconmicrostriptrackerhassingle-pointresolutionofbetween23mintherdirectionand230minz. 23 25 ]reducestheeventrateof40MHzdowntotherateofO(100)Hz,whichcanbewrittentoarchivalmedia.Suchreductionisachievedwithhelpofadjustabletriggerthresholdswhichallowtolterorprescalemostofthe 41

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4-12 onecanseethesinglemuonrateisasteeplyfallingfunctionofmuonpTthreshold. IntegratedrateofsinglemuonsfromPYTHIAeventgenerator[ 21 ]asafunctionofthemuonpTthresholdandforluminosityL=1034cm2s1[ 24 ].Thebreakdownofthemuonsourcesisalsoshown. Thetriggersystemisorganizedinto2successivesteps.TherststepisreferredtoasLevel-1trigger.TheLevel-1Triggerconsistsofcustom-builthardwarecomponents.Itselectinterestingeventswithcertainsignatures(e.g.highETorEmissingT,jets,electrons,muons,taus)usingtheinformationfromthecalorimetersandfromthemuondetectors.Finally,within3.2sitprovidesadecisionandsendsittotheTriggerTimingandControl(TTC)system,whichinturnnotiesthedetectorfront-endelectronicstostartthefullread-outprocess.Thisrststepallowstoreducetherateof40MHzdownto100kHzorless.Thesecondstep(socalledHigh-LevelTriggerorHLT),isdoneonafarmofO(1000)conventionalPCs.TheHLTdoesregionalreconstructionintrackerusingLevel-1triggerseeds.Itisbasedonsoftwaresimilartotheofinereconstructionand 42

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43

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23 ].Thenetworkofcathodecomparatorsonthefront-endboardsndsthetrackhitpositionineachofthe6layersinsidethechamber.Itidentiesthestripwiththepeakchargeandlocalizesthehitpositiontoeitherleftorrighthalfofthestripbycomparingthepulsesontheneighboringstrips.Theanodesegmentationismuchcoarserandthecircuitryisoptimizedfortimingratherthanpulseheightmeasurement.Figure 5-1 showsblockdiagramoftheCSCtriggersystem.ThedigitalsignalsgeneratedbythecathodecomparatornetworkarebroughtintothecathodeLocalChargedTrack(LCT)processors.ThelogicpulsesfromtheanodediscriminatorsareusedbytheanodeLocalChargedTrack(LCT)processors.Theprocessorsndtrackroadsthroughthe6layersofcathodesandanodes.TheLCTlocation,itsangle,andbunchcrossingtimearereportedbytheprocessorstotheTriggerMotherBoard(TMB).IfthetimingbetweencathodeandanodeLCT'sisfoundtoagreewithinanadjustablewindowofupto2bunchcrossings,theTMBcombinesthecathodeandanodeLCTsintothe2dtracksegments,knownasCorrelatedLCTs.WhenmorethanoneCorrelatedLCTisfoundbytheTMB,onlythebesttwo,asdeterminedbyqualityfactors,areretained.Hence,everychambercanreportonlyuptotwoCorrelatedLCTs.Thetracksegmentsfoundineachstationaretransmittedovertheopticalcablestoaregionaltriggersystem,calledtheCSCTrack-Finder[ 26 27 ].ThepurposeoftheTrack-Finderistoconnecttracksegmentsdeliveredbythestationsintoafullmuontrackandassignitwithatransversemomentum,pseudo-rapidity,andazimuthalangle.Thetransversemomentumisassignedusingthedifferenceinthespatialcoordinateofthetracksegmentsinuptothreestations.ItallowstoachieveapTresolutionofabout25%.ThisissufcienttoachieveasuitablesinglemuonratewithareasonablepTthreshold. 44

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DesignoftheCSCMuonTrigger. TheCSCtriggersystemispartitionedintosix60azimuthsectorsineachendcap(Figure 5-2 ).TheCSCTrack-Finderconsistsof12SectorProcessor(SP)boards,theMuonSorter(MS)boardservingasaninterfacetotheGlobalMuonTrigger,theClockandControlBoard(CCB),whichsynchronizestheCSCTrack-Findercratewiththerestofthedetector,andthecratecontrollerconnectedtoadedicatedPC.TheCSCTrack-FinderalsosavesitsinputandoutputdatabymeansoftheDetectorDependentUnit(DDU)totheDataAcquisition(DAQ)stream.Additionally,asetofTransitionBoards(TB),connectedtothecommonelectronicbackplanefromtherearsideofthecrate,providesinterfaceforthecommunicationbetweentheDTandCSCTrack-Findersintheoverlapregion,0.9
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SchematicviewoftheCSCTriggerSectoracross4stations. 46

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47

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48

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SectorProcessorTransitionBoard SectorProcessorMuonSorter MuonPortCard!SectorProcessor SectorProcessor!DetectorDependentUnit 5-3 ).Thetriggerwasprovidedbyasetofscintillatorswhenmuoncausedcoincidentsignalsbetweenscintillatorlayers.Theteststandwasusedtodevelopcongurationandreadoutsoftware. 49

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PhotographoftheUFcosmicteststand. machineclock.Initialprotonsinthisbeamwereorderedinatrainof48consecutivebunches,andthetotalorbitlengthwas924bunches(Figure 5-4 ). Timestructureofthetestbeam. 50

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5-5 .ThetwoCSCswereconnectedtoonePeripheralCrate.TwoDAQMotherBoards(DMBs)inthecrateservedtheDAQreadoutdatatotheDDUboardintheseparatecrate.ThesedatawereeventuallyloggedonaharddriveofthePC,interfacedtotheDDUwith1Gbethernetopticallink.TwoTriggerMotherBoards(TMBs)inthePeripheralCrateservedtriggerprimitivestotheMuonPortCard(MPC)inthesamecrate.TheMPCsortedthe3besttriggerprimitivesandsendthemtotheTrack-Findercrate.ThePeripheralandTrack-FindercratesweresynchronizedbytheTriggerTimingandControl(TTC)moduleintheTTCcrate.TheTTCmodulewaslockedtothemachineClocksignalwith40.079MHzfrequency.Thetriggerwasprovidedbythelayersofscintillators. Schematicviewofthebeamtestsetupin2003. Thebeamtestof2003exposedaproblemoflinksynchronizationbetweentheMPCandSPboardsduetotheexcessiveLHCclockjitter.Asaresult,aphase-lockloop(PLL)wasaddedtotheTrack-Findertocleantheclocksignalfortheopticallinkreceivers.AdedicatedbeamtestinSeptember2003showedthatsynchronizationwasmaintainedwiththePLL. 51

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5-6 .OneResistivePlateChamber(RPC)withaseparateDAQsystemwasalsoaddedtotheconguration.TheRPCsignalswerebroughttotheCSCTriggerMotherboardbytheRPCAnodeLCTTransition(RAT)module.TheRATmoduleusedshowednoiseproblemsduringthetests.ForthersttimetheCSCTrack-Finderwasusedasasourceoftrigger,demonstratingtheselftriggeringcapabilityoftheCSCs. SchematicviewofthebeamtestsetupinJuneof2004. InOctoberof20044PeripheralCratesgathereddatafrom5chambersinasynchronousbeamintheH2northareaofCERN.Alsoexposedtothesamebeamwere3RPCsand1HCALmodule,eachwithitsownseparateDAQsystem. 52

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5-7 ).Themainpurposeofdatatakingin2005wassupportingthecommissioningoftheMuonEndcap(EMu)system.InordertofacilitatethistaskanautomatedanalysisprocessoftheDataQualityMonitoringsetupwasdeployedinUF.ItproducedasetofcomprehensivedistributionsandchecksfortheCSClocalDAQdataeverytimenewrunwasrecordedatCERN.Theresultswerepublishedonthewebprovidingavaluablepromptfeedbackforthecommissioningteam. 53

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ChambersparticipatingintheSliceTestof2005. Unlikeparticlesoriginatingfromthecollisionvertex,cosmicparticlescrossthesystemunderallpossibleinclinationsandmaynotgenerateatriggerastheCSCtrackndinglogicsearchesforcollisionpointingtracks.Inordertorelaxthisconditionaspecialmodeoftriggering,onanysingletriggerprimitivearrivingattheCSCTrack-Findercrate,wasaddedthermware.Thismodewasusedasadefaulttriggeringmodethereafter. 54

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5-8 belowshowsthearrivaltime(x-axis)oftriggerprimitivesfromallthechambers(y-axis)withrespecttoasinglechamber.Inaperfectlytimedsystem,themajorityoftriggerprimitivesfallintothecentral'zero'binandsmallsymmetrictailsof1bunchcrossing.Basedontheseplotslocaladjustmentsweremadetotheindividualtriggerpathlatenciesandanaccuracyof1bunchcrossinghadbeenachievedbytheendoftherunperiod.TheDQMprocesswascontinuouslyrunningthroughallthelocalCSCdataeversince. 55

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Timeofreceivingtriggerprimitives(LCTsandDTstubs)fromtriggersector#4intheCSCTrack-FindercraterelatedtothetimeofLCTs,receivedfromasinglereferencechamberinthissector. 5-9 ).TheME+endcapwasloweredattheendof2006.ItwasusedfortheundergroundSliceTestwithcosmicrays.TheME-endcapwasundergoingcommissioningaboveground,beforeitwasloweredinJanuaryof2008.ThemainpurposeofthecontinuingSliceTestdatatakingwasthecommissioningoftheCSCsystem.CommissioningoftheCSCTrack-Finderatthattimefocusedondevelopmentofthermwareandsoftwareaswellasontheoptimizationofthetrack-ndingalgorithms.Someofthesuccessofthisworkinclude: 28 ]. 56

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TheCSCTrack-FindercrateintheUSCundergroundcavern. 29 ]. 57

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30 ].Sizablesamplesof300millioncosmiceventswereaccumulatedandusedforawiderangeofanalysesoftheCMSdetectorperformance,includingameasurementofthemagnitudeofthemagneticeldinthereturnyoke[ 31 ],track-basedalignmentstudies[ 32 ],andmeasurementoftheatmosphericmuonchargeratio[ 33 ].TheLevel-1CSCTrack-Finderperformanceanalysesinclude: 29 ].InthenextsectionofthisdocumentwefocusontheanalysisoftheCSCTrack-Findertriggeringandtrack-ndingefciencies. 58

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5-10 theshiftalsocompensatefor 59

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Thetimedifference(inbunchcrossings)betweenLCTsinthetoppartofoneendcapandthebottompartofanotherendcap.Effectively,thisisthetime-of-ightbetweenthetwoendcapsasseenbytheCSCTrack-Finder. Figure 5-10 showsthatthetoppartoftheendcapmuonsubsystemislikelytogenerateanLCTearlierintime.Thatallowstomeasuretriggerefciencyinthebottompartoftheendcapmuonsubsystem.OnecouldmeasuretriggerefciencyinthetoppartofthedetectorusingeventswithtriggeringLCTinbottompartatthesametimeorearlier.Anincreaseinthetimedelaybetweenthetopandthebottomcouldgiveusmoreeventsofthiskind.Unfortunately,suchtimedelayswerenotexercisedandweareunabletoreproducetheefciencymeasurementinthetoppartofthedetectorwiththeprecision,similartotheprecisioninthebottompart. 60

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5-11 ),whichstemsforthefactthattheatmosphericmuonsarrivefromthetop.Therefore,propagationtothetoppartofthedetectorreceivesanextra:propagated=track+8><>:0propagationtothebottompropagationtothetopThechoiceofsignintheequationdependsonthemuoncharge.Anadditionalspacialcutof1.1
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Theoftrackertrack(ontheleft)andtriggerprimitive(ontheright). theconsequenceofloosecutonthelongitudinalimpactparameterofthetrack(i.e.DOZ<50cm).3ThedistributionsuggeststhatifLCTexists,itislikelytobefoundwithin0.3windowaroundthepropagatedtrack's.Figure 5-13 showstheefciencytogenerateanLCT(andeventuallytoreatrigger)forthetopandbottomsectorsofthebothendcaps.4Inthebottomsectorstheefciencywasfoundtobegreaterthan99%on2KeventswithI.P.pointingtracksofpTabove20GeV/c.Thetopsectorssufferfrominsufcientstatistics(only300events).Theaverageefciencythereisgreaterthan98%. 62

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Differencebetween(ontheleft)and(ontheright)coordinatesofthetriggerprimitiveandtrackertrack. EfciencyofCSCLevel-1triggerasafunctionofofinereconstructedpTinthetracker.Ontheleft:efciencyforbottomCSCsectors,ontheright:topCSCsectors. relativetothesinglesmode,wasmeasuredbyconsideringallCSCTFcandidates(singlesandcoincidence),andcheckingforavailablesegmentsinthesametimebin,whicharespatiallyclosetotheCSCTFcandidate.Ifsegmentswhichcouldforma 63

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5-14 EfciencyofCSCTFtobuildamuoncandidatefromseveraltracksegmentsseparatedinbinsofaqualitytagassignedbytheCSCTFalgorithms. 64

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21 ]iswidelyusedformanyphysicsstudiesincludingtheonepursuedinthisdocument.Theprogramcontainstheoreticalcalculationsandmodelsforanumberofaspectsofthecolliderphysics.Theprobabilityofacertainsoftorhardinteractionbetweentwopartonsismodeledaccordingtothepartondistributionsfunctions.Thepartonscanscatterorannihilateandproduce,forexample,aheavyresonance(e.g.Z,W,exoticparticle)asrequestedinthecongurationfortheprogram.Theresonancethendecaysasparametrizedbythematrixelementandphasespacecalculation.Theinitialpartonsmayradiateacolor-chargedparticle,whichseedstheevent'sinitialstatepartonshower.Thehardinteractionbetweenthetwopartonsimpactstheotherpartonsthatareleftintheprotons.Thenon-perturbativesoftQCDinteractionsbetweentheremainingpartonsaredescribedbyaphenomenologicalmodeloftheunderlyingevent,andtheproductsoftheunderlying 65

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34 ]wasusedtomodelvariousbackgroundsfortheDrell-Yanproduction,whichweusetostudyspectrumofthetransversemomentumofZ. 35 ].ThepackageisincludedintotheCMSofinesoftwareframework(CMSSW),whichholdsthedescriptionofthedetector'sgeometry,material,andmagneticeld.Theenergydeposits,leftbytheparticle,arethenconvertedintotheelectronicreadoutsignals.ThisisaccomplishedbyasetofCMSSWsimulationsoftwarepackages,whichmodeltheelectronicsofeverysubdetector.Theseelectronicsignalsarestoredinthedatacollections,whicharereferredtoasdigicollections.Thedetectorreconstructionstartsfromthedigidata.Thispartoftheofinedetectorsoftwaredoesnotdiscriminatebetweensimulateddataandrealdatafromthedetector.Itappliesthedetectorcalibrationandalignmentconstants(trivialinthecaseofsimulation).Itbuildstracksfromhitsinthetrackersystemandclustersenergydepositsinthecalorimeters.Intheenditreconstructsthecompletephysicsanalysisobjects(muons,photons,jets,etc). 66

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17 ],Z0[ 16 17 ],orsomeSUSYparticles[ 19 ])decayingtotheZmayproduceanexcessofeventsinhighpTrangeoverthestandardDrell-Yancontinuum.ThelatestmeasurementsofpTspectrumoftheZwasperformedbyCDF[ 44 ]andD0[ 45 ]collaborationsattheTevatrononppcollisions.RecentresultsfromD0collaborationuse0.98fb1ofdata,takenat1.96TeVcenter-of-massenergy.PreviouslypublishedresultsfromCDFandD0collaborationsusedanintegratedluminosityof110pb1at1.8TeVcenter-of-massenergy.TheLargeHadronCollider(LHC)center-of-massppcollisionenergyof7TeVprovidesroughly3timesgreatercrosssectionfortheprocess.WiththerstperiodofrunningattheLHCin2010weexpecttocollectupto100pb1[ 46 ].TheanalysisoftheZbosontransversemomentumdistributionwasperformedontheMonteCarlosimulationdata,generatedat10TeVcenter-of-masscollisionenergy,availableatthetime.Comparingittothepreviousstudywith14TeVcollisionenergy(summarizedinappendixA)weconcludethattheeventselectionefcienciesbehavesmoothlyasfunctionsthecollisionenergy.SameappliestothecrosssectionsoftheZbosonproductionandleadingbackgrounds.Therefore,wedonotexpectdramaticallydifferentresultsforthe7TeVLHCcollisionenergyscenario.InthispaperwefollowconventionsofD0publication[ 45 ],andrefertothepTofZ=asqT. 67

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47 ].Figure 7-1 showssomeofcorrespondingFeynmandiagrams. Feynmandiagramsforzerothorder(left),next-to-leadingorder(middle),andsomediagramsfornext-to-next-to-leadingorder(right)Drell-Yanproduction. Pythia[ 21 ]andMC@NLO[ 49 ]eventgeneratorswereusedforDrell-Yanproductionsimulation.TheFEWZzprogram[ 15 ],capableofcalculatingcrosssectionoftheprocessinzerothorder,NLO,andNNLOforvariousexperimentalcutswasalsousedinthisstudy.WiththehelpofthisprogramweestimateuncertaintiesinpTspectrumofZpredictedbytheory.Applyingconstraintsonthemassoftheintermediateboson66GeV/c2
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16 17 ],supersymmetricparticles[ 19 ],orhighmassexcitationsofstandardmodelparticlesinthetheoryofextradimensions[ 20 ].Figure 7-2 isanexampleoftheqTspectrumfortheZ!processwithsuperimposedmuondecaysofZ0andW0inPythia'smodelofnewgaugebosonswheremassesforbothbosonsweresetto1000GeV/c2. TheanalysisoftheqTspectrumisamodelindependentanalysis.Therefore,inthisstudywedonotpreferanyparticularmodeloverothermodels. 69

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7-3 .ThecrosssectionforthehighqTtail(qT>30GeV/c,23%ofeventsatp 45 ].HardgluonemissioniswellmodeledbyperturbativeQCDcalculations,whichareimplementedinvariouseventgeneratorsandprogramsevaluatingthecrosssectionoftheprocess(e.g.Pythia,MC@NLO,FEWZz).Variouseventgenerators(e.g.Pythia)alsoreproducethesoftpartoftheqTspectrum.Thenon-perturbativenatureofQCDinteractionsinthisregionisusuallyparametrizedinseveralcoefcients,whicharetunedtomatchthedata.Intheend,theperturbativeandnon-perturbativepartsoftheqTspectrumshouldmatchintheintermediateregion(qT30GeV/c). ShapeoftransversemomentumdistributionofZbosongeneratedbyPythiainproton-protoncollisionsatp Sincetheaccumulatedrealdataof2009areinsufcientforthisstudy,weonlycomparetheshapeoftheqTdistributionsgeneratedwithseveralbasicPythiatunesaswellasMC@NLOandFEWZzprograms. 70

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7-4 showstheratiosoftheqTspectra,producedwithPythia6.416tunesDW,DWT,Atlas,andA[ 39 ].Asonecanseefromtheplot,tuneAisverysimilartotuneAtlasandtuneDWisclosetotuneDWT.ThesetwogroupsoftunesproduceverydifferentqTplots.ThemostsignicantdifferencebetweenthetwogroupscomesdowntotheinitialstateradiationandprimordialkTparameters.Asitwasshownin[ 50 ],primordialkThasverylittleeffectontheqTspectrum.AmongPythia'sremainingunderlyingeventparameters,onlyonesingleparameter,theprefactorofthemomentumscaleforrunningsinspace-likeparton-showerevolution,affectstheqTspectrum. RatioofqTspectrafor4standardPythia'sUnderlyingEventtunes. PublicMonteCarlosamples,usedfortherestofthisanalysis,areproducedwiththedefaultPythiatuneDW. 71

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7-5 onecancompareNLOandNNLOpredictionsoftheqTspectrum,generatedbyFEWZzprogramwithCTEQ6.6functions[ 51 ].TheFEWZzcalculationssuggestfactorof1.4.9excessofNNLOoverNLOinthehardpartoftheqTspectrum. Hardpart(qT>30GeV/c)ofthenormalizedqTspectruminlinearscale(left)andinlogscale(right).GreendotsPythiaresults,redtop-pointingtrianglesNNLOFEWZzresults(CTEQ6.6),bluebottom-pointingtrianglesNLOFEWZzresults(CTEQ6.6),cyanstarsMC@NLOresults. 7-1 ).TheabsolutenumberofeventsineachoftheqTbinsisproportionaltotheintegratedluminosity.WenormalizetheqTspectrumto1tocancelerrorsinknowingthe 72

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BinningoftheqTspectrum.LastcolumnestimatesnumberofDrell-YaneventsfromZpeakwithbothmuonswithinthesinglemuontriggeracceptance(jj<2.1)for10pb1atp centerof acceptance #events Range centerof acceptance #events (GeV/c) mass per10pb1 mass per10pb1 0.672 0.349 60 16 16.5 0.396 119 1.5 1.26 0.349 73 17 17.5 0.397 111 1.5 1.76 0.350 96 18 18.5 0.399 104 2.5 2.26 0.351 113 19 19.5 0.401 97 2.5 2.75 0.352 125 20 21. 0.404 178 3.5 3.25 0.354 133 22 23. 0.407 156 3.5 3.75 0.355 138 24 25. 0.412 139 4.5 4.25 0.357 138 26 27. 0.415 124 4.5 4.75 0.359 136 28 29. 0.419 111 5 5.5 0.362 263 30 32. 0.425 192 6 6.5 0.366 246 34 36. 0.432 158 7 7.5 0.370 229 38 40. 0.441 131 8 8.5 0.374 212 42 44. 0.449 110 9 9.5 0.377 196 46 48. 0.456 93 10 10.5 0.380 182 50 54.6 0.470 178 11 11.5 0.383 168 60 64.6 0.490 121 12 12.5 0.385 158 70 74.6 0.510 83 13 13.5 0.388 147 80 88.8 0.536 102 14 14.5 0.390 136 100 118. 0.588 93 15 15.5 0.392 127 150 170. 0.671 23 73

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7.3.2 describeshowthisefciencycanbemeasuredfromthedatausingthetag-and-probemethod.Thedoublemuontrigger,asitwillbeshowninthefollowingsection,doesbetterbackgroundsuppression,butisslightlylessefcienttosignalevents.Thus,fortheveryrstLHCdatawechoosetousethesinglemuontrigger.Table 7-2 denestheselectioncriteriaofthesepaths,usedforL=1031cm2s1,10TeVscenario. Table7-2. Triggerpathsusedforthe10TeVscenario(L=1031cm2s1).Neitherpathisprescaled. HLTpath Triggername L1seed HLTpT threshold parameter Single Mu9 L1 SingleMu7 9GeV/c dxy<2cm Double DoubleMu3 L1 DoubleMu3 (3,3)GeV/c dxy<2cm 74

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DoubleMu3yieldsapproximatelya1:8ratioofsignaltobackground(whichismostlyQCD).TherelaxedsinglemuonHLTpath(HLT Mu9)contains99%ofbackgroundafterskimmingprocedureisapplied.TheseresultsaresummarizedinTable 7-3 Table7-3. Thenumberofeventsaftereachselectionstep.TheLOcrosssectionoftheW+jetsandttprocessesscalesdownto70%at10TeVcollisionenergycomparedto14TeV.FortheZ!backgroundprocess(lastrow)thegeneratorlevelcutontheinvariantmassofwassetat40GeV/c2for14TeVscenarioandat20GeV/c2for10TeV(thesetwocutschangethecrosssectionroughlybyafactorof2atthesameenergy).TheQCDbackgroundishigherforthe10TeVscenariobecauseHigh-Leveltriggersapplylooserimpactparametercut(dxy<2cmasopposedtodxy<0.02cmfor14TeV). #ofevents Global,jj<2.1 HLT Mu9 Weighted Compared inSummer08 DoubleMu3 to10pb1 918K 788K 769K 5.3K 72% 4.6K 75% Inclusive 5.3M 3.2K 1.96K 439K 118% 37K 319% 9.8M 1.6M 1.4M 58K 79% 6K 250 83% 225K 197K 624 48% 58K 184 69% 56K 49K 799 133% 5.5K 90 150% 45 ]).Thesecondselectioncriterionmakeuseoftracker-basedmuonisolation.Tracker-basedmuonisolationisdenedasacutonasumoftransversemomentaoftrackertrackswithpT>1GeV/cspatiallyclosetotheglobalmuon.Suchtracksarelookedforinthe 75

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7-4 showstheefciencyofthisselectiononsignalandbackgrounds.Onecanseethatrequiringanymuontobeisolatedsuppressesallthebackgroundstothelevelof102orbetterwithrespecttothesignal. Table7-4. Theperformanceofthecutontheinvariantmassandthetracker-basedmuonisolation. #ofevents Second,jj<2.1, Invariant Eitherof isisolated 5.3K 4.1K 3.9K 3.9K 3.7K 3.5K 3.5K Inclusive 439K 7.3K 730 0 3K 487 0 58K 36 12 12 0.25K 11 5 5 66 22 20 184 54 19 17 18 3 3 90 15 3 3 7-6 showstheqTdistributionfortheDrell-Yanprocessandtheleadingbackgroundsafterapplyingallthecuts. 76

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TheqTdistributionforthesignalandtheleadingbackgrounds(stacked)in10TeVsampleafterapplyingtheselectioncuts. 77

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7-7 showssuchinvariantmassdistributionsfortracksfromdifferentpTregions.Variousmethodsaccountingforthisbackgroundcanbeappliedtocalculatetheefciency.Oneofthemisthesidebandsubtractionmethod.ThemethodinstructsonetochooseleftandrightsidebandssothatthenumberofeventstherewillmatchtheexpectedcontributionsfromtheDrell-YancontinuumandotherbackgroundsinsidetheZ-masswindow(assumingthatbothcontributionsaresmoothfunctionsofinvariantmass).Thenitcorrectsthenumberoftriggersunderthepeak(thenumeratorinthetriggerefciencycalculation)bythenumberoftriggersintheleftandrightsidebands.Itdoesthesametothetotalnumberofdi-muoncandidates(denominator),correctingitbythenumberofcandidatesinthesidebands.Todemonstratehowthemethodworks,letusdenotewithN(trig,Z;L=R=C)thenumberofeventsfromtheZresonancewhichhaveaprobetrackringthetrigger. 78

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Distributionofinvariantmassoftagmuonandtrack.Bluemuonwithanytrack.Greenmuonwithtrack,matchingstandalonemuon.LeftplotpToftrack<5GeV/c,middlepToftrackisin[15]GeV/cregion,rightpToftrackisin[40]GeV/cregion. 79

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80

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7-8 showstheefcienciesofLevel-1,Level-2,andLevel-3muontriggeralgorithmsasfunctionsofthepTofthemuonforthedetectoralignmentlevelthatisexpectedtobereachedafterprocessing10pb1ofdata(referredtoasthe10pb1misalignmentscenario).Themuontriggerefciency,extractedwiththetag-and-probemethod,showsgoodagreementwiththeefciency,measuredusingtrueMonteCarloinformation,formuonswithpTabove20GeV/c.Intheregionbelow20GeV/c,thetag-and-probemethodgivesbigsystematicaluncertaintiesduetoahighbackgroundlevel.ThisfeaturedoesnotaffecttheanalysisaspT>20GeV/cistheofineselectioncut. 81

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EfciencyofthesinglemuontriggersasfunctionsofpT(leftplots)and(rightplots).TherstrowcorrespondstoLevel-1trigger,secondLevel-2,andthirdLevel-3.MonteCarlobluedots,tag-and-probewithsidebandsubtractionredtriangles.Theresultsareobtainedon25pb1ofDrell-Yanproduction. therstdataduetotheunknownmisalignmentandresultingpotentiallyhighinefciencyofthet.Therefore,resultingglobalmuonreconstructionefciencywillbeaproduct 82

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7-9 EfciencyofmuonreconstructionasafunctionofpT(leftplots)and(rightplots).Therstrowcorrespondstostandalonemuonreconstruction.Secondefciencyofsilicontrackertoreconstructmuontrack.MonteCarloisinblue,tag-and-probewithsidebandsubtractionred. 83

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84

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7-10 representstheMonteCarloefciencytotriggeronadi-muoneventwithbothmuonspassingthekinematiccutsofjj<2.1,pT>20GeV/c,and66GeV/c2
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MonteCarloefciencytotriggerthedi-muonevent,whichpassesthekinematiccutsusingthesinglemuontrigger. TheMonteCarloefciencytoreconstruct2trackermuons,whichpassthekinematiccutandtriggerthesinglemuontrigger. Letusdeneeasaratioofthenumberofeventswithtwoisolatedmuons(N)tothenumberofdi-muoneventswithatleastoneisolatedmuon(N).Letusalsodenotetheunknownefciencyoftheisolationcut,appliedtoasinglemuonfromsignalsample,as.Muonsfromthesignalsamplearemostlyisolatedand=1,whereisasmallnumber,representingtheinefciencyofthecut.Assumingnocorrelationbetweenthe 86

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2(1+e).TherealdataalsoincludenonDrell-Yanmuonpairs.Thesecondmuoninthepairfrombackgrounddoesnothavetobeisolated.Therefore,sucheventsintroducebiastothemethod.Asitwasshowninsection 7.3.1 ,requiringasingleisolatedmuoninthedi-muoneventssuppressesbackgroundstothelevel102.Wetakethisvalueasthelevelofthesystematicuncertaintyrelatedtothemethod.Figure 7-12 showstheefciencyofthecutonthestandardtracker-basedisolationparameter.OnecanseetheefciencydropsrapidlyasthetransversemomentumofthemuonpairapproachesroughlyhalfoftheZmass.ThisisaconsequenceoftheunderlyingeventrecoilingagainsttheZandproducingmorechargedparticles,ascanbeseeninFigure 7-13 .ThedropoftheisolationcutefciencyisattributedmostlytothelowpTmuonofthedi-muonpair.IthappensbecausethehighestpTmuonislikelytotravelalongthedirectionofZ,receivingapositiveLorentzboost,whilethelowpTmuontendstotravelinoppositedirection,alongwiththerecoilingunderlyingeventparticles.Thesameeffectexplainstheriseoftheisolationcutefciencyabove40GeV/c.Ifboostedhardenough,moremuonsyintheforwardhemisphereofthedirectionofboost,awayofmostoftherecoilingunderlyingevent.InFigure 7-14 wecomparetheMonteCarloisolationcutefciency(ratioofeventspassingthecuttototalnumberofevents)forthehighestandthelowestpTmuonsfromthepair,superimposedonthedata-drivenefciencymeasurement.ItalsoshowsaproleplotoftheangleintheXYplanebetweenthe~pTofZandthe~pTvectorsofthemuonsfromthepair. 87

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Thedata-drivenefciencymeasurementofthestandardtracker-basedisolationcutonasinglesignalmuon. DensityofchargedparticlesasafunctionofthepTofthemuonpair. Figure 7-15 showsboththeefciencytoacceptadi-muoneventifanymuonfromthepairpassestheisolationcutandtheefciencywhenbothmuonsfromthepairpassit.Asonecansee,requiringonlyonemuonfromthepairtobeisolatedleavesmuchlessspaceforthevariationoftheefciencycurveandmakesmuchlessbiasonthe 88

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Ontheleft:MonteCarloisolationefciencyforthehighest(redtop-pointingtriangles)andthelow(bluebottom-pointingtriangles)pTmuonsfromthepair.Greendotsthedata-drivenmeasurement.Ontheright:proleofangleinXYplanebetween~pTofZand~pTvectorsofthemuons(highestpTred,lowpTblue)fromthepair.Horizontalline=separatesforwardandbackwardhemispheresalongthedirectionof~pTofZ. measuredqTshape.Ifbothmuonsarerequiredtobeisolated,themeasuredqTshapeneedstobecorrectedbythevariationoftheefciencycurveofabout2%. Redtop-pointingtrianglesefciencyofanymuonfromthedi-muoneventtopasstheisolationcut.Bluebottom-pointingtrianglesefciencyofbothmuonsfromthepairtopasstheisolationcut. 89

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7-16 showsdistributionofpTptrueT 7-5 presentstheresolutionaswidthofthesinglegaussiantintworangesandTable 7-6 showsthetworesolutionparametersofthedoublegaussiant.Theinitialdataaresplitintoseveralsubsamplesandthetsareperformedindependentlyoneachofthem.Theresultingparametersareaveragedandthestandarddeviationistakenasanuncertainty. Table7-5. Thewidthofasinglegaussian,ttingthepTptrueT 2.400.15 2.580.08 7-17 demonstratesresolutionofmuontransversemomentummeasurementandwidthofZpeakforthetwomisalignmentscenarios. 32 ]. 90

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DistributionofpTptrueT Table7-6. Theresolutionparametersofthedoublegaussiant. Ideal(%) Start-up(%) 2.180.27 4.350.72 53 ]package.Thisfunctionisaconvolutionofasimplenon-relativisticBreit-Wignerwithgaussian:V(m,M,,)=1 (mM)2+1 4)]TJ/F8 7.97 Tf 6.77 3.45 TD[(2exp1 2m

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Muontransversemomentumresolution(left)andinvariantmassofthemuonpair(right)fortwomisalignmentscenarios:idealalignmentredbottom-pointingtrianglesandstart-upalignmentbluetop-pointingtriangles.GraphsontheleftplotrepresentthemuonpTresolutionasthewidthofthecentralpeakofthedoublegaussianfunction,ttingthepTptrueT whereemandemareterms,parameterizingPDFs.6ThetisdonewithZbosonwidthxedatitscurrentPDG[ 18 ]value(i.e.)-325(=2.49520.0023GeV/c2).Figure 7-18 showstsofdi-muoninvariantmassatthelevelofgeneratorandafterthefullCMSsimulationwiththeidealandthestart-upalignmentscenarios.Approximatingtheresolutionbyasinglegaussianintroducessomesystematicerroronthetparameters.Ifthetrueresolutionhasnon-gaussiantails,theypullthewidth 92

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FitoftheZresonance.250pb1areusedinthedistributionsforthegeneratorandforthefullsimulationwiththeidealalignment.Forthestart-upscenarioweuse10pb1ofDrell-Yanproduction. ofthettinggaussian.Table 7-7 showstheresolutionparameteroftheZpeaktinseveralrangesofthemuoninvariantmass.Averagingtheresultsfromthetableweobtain=1.250.05GeV/c2fortheidealalignmentand=2.510.20GeV/c2forthestart-up. Table7-7. Theresolutionparameter,,extractedfromthetoftheZresonanceinseveralranges.Theuncertaintyforthestart-upscenario(only10pb1ofdata)istakendirectlyfromthet.Forthegenerator-leveldataandfortheidealalignmentscenarioweestimatetheuncertaintyasthestandarddeviationofthe,evaluatedonseveralsubsetsoftheinitialdatasample. 84
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mtrue+m mtrue2=2(p1ptrue2+ptrue1p2+p1p2)(1cos) 2ptrue1ptrue2(1cos),2m mtrue+m mtrue2=p1 mtrue1andp ptrue1:2m mtruep1 94

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7-19 showsaratioofthegenerator-levelqTspectrumshapetotheqTspectrumshapeafterthefullCMSsimulation. RatiooftheqTspectrumshapeonthelevelofgeneratortotheqTspectrumshapeafterfullCMSsimulation.Theplotisproducedon1fb1ofdata(100pb1misalignmentscenario). Thereareseveralwaystoaccountforthiseffect: 7-19 andappliesthemtotheqTspectrumfromtherealdata.Theresultingsystematicuncertaintyofthemethoddependsonhowwellthedetectorismodeled. 95

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7-20 onecanseetheunfoldingcorrectionsforthestart-upandtheidealalignmentscenarios.OnecannoticethattheunfoldingcorrectionsattenoutaboveqT=10GeV/canddonotaffecttheshapeoftheqTdistribution. 7-21 showsthecrosssectionoftheprocess,calculatedinNLO.VerticalbarsarethedifferencebetweenthevalueofthecrosssectionforbothscalessetatthemassofZandmaximum/minimumvaluesofthe 96

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Theunfoldingcorrectionsforthestart-upalignmentscenario(left)andfortheidealalignmentscenario(right).ToprowqT<30GeV/c,bottomrowqT<200GeV/c.Thesystematicuncertainty(shadedarea)forthecorrectionfactorsisdiscussedindetailinsection 7.3.4.2 ontheexperimentalsystematicuncertainties. crosssectiononthegrid.Thelargestuncertaintyofroughly20%correspondstothelowqTbins.Itcomesdownto10%forthehighqTvalues.ThesamecalculationcanbedoneintheNNLO.Weskipthiscomputationallyexpensiveexerciseandestimatethecorrespondinguncertaintytobesuppressedbythefactorofs=.Thatleavesuswith1.5%1%uncertaintyfortheNNLOqTspectrumprediction. 97

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Ontheleft:normalizeddifferentiald=dqTNLOcrosssectionwitherrorsduetofactorizationandrenormalization.Ontheright:absolutescaleoftheuncertaintyonthedifferentialNLOcrosssectionasafunctionofqT 51 ]andMSTR2006nnlo[ 54 ]generationsofPDFsallowonetoestimatethisuncertaintybyvaryingtheHessianeigenvectorsinthePDFparameterspace,asitisdescribedindetailin[ 55 ].TheresultinguncertaintiesontheabsolutecrosssectionandontheqTspectrumshapeareshowninFigure 7-22 .Theywereobtainedfora14TeVcollisionenergy. 98

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PDFuncertaintiesinthecrosssection.CTEQ6.1bluetop-pointingtriangles,MRST2006nnloredbottom-pointingtriangles.Ontheleft:differentialcrosssectionuncertaintiesinseveralqTbins.Ontheright:uncertaintyonratioofdifferentialcrosssectionineachqTbintototalcrosssectionoftheprocess. theleftandrightsidebands,requiringthetotalnumberofeventstheretomatchtheexpectedcontributionfromthebackgroundeventsandtheDrell-YancontinuumundertheZpeak.Thetechniquethencorrectsthenumberofeventsinthenumeratorandinthedenominatoroftheefciencyestimatorassumingthatthenumberofbackgroundeventsinthecentralregionisthesametothenumberofbackgroundeventsinthesidebands.Insteadoftestingalltheassumptionsusedinthistechnique,weestimatethesystematicerrorofthetagandprobemethodlookingattheresultingefciencywithandwithoutthesidebandsubtractiontechnique.Asanexample,Figure 7-23 showsthecombinedLevel-1andHigh-Leveltriggerefciencyofthetagandprobemethodwithandwithoutthesidebandsubtraction.Onecanseethattheturn-oncurvesmatchwithinthestatisticalerrorbarsforpT>20GeV/c.TheaverageefciencyforpT>20GeV/cis87%withthesidebandsubtractionand86%without.Therefore,weconsidertheuncertainty,comingfromtheefciencymeasurement,tobeontheorderof1%. 99

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Bluebottom-pointingtrianglestagandprobewithoutthesidebandsubtraction,redtop-pointingtrianglesstandardtagandprobewiththesidebandsubtractiontechnique. ThelowqTpart(.10GeV/c)ofthespectrumreceivesthebiggestdistortionsduetothenitedetectorresolution.Weevaluatethebin-by-bincorrectionsandestimatethecorrespondingsystematicuncertaintiesusingseveraltoyMonteCarlomodels.Thesemodelsshiftthegenerator-levelpTofeachmuonbyarandomnumber.Thereferencesetofthebin-by-bincorrectionsisproducedwiththemodel,whichgeneratearandomparameter,,distributedas(pTptrueT)=ptrueT.Weusethe10TeVsimulateddata(idealalignmentscenario)andproducetheprobabilitydensitydistributionsin30equal-sizebinsfromtherangejj<2.1and30equal-sizemuonpTbinsfromtherange20GeV=c
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Bin-by-bincorrectionfactorsforthestart-upalignmentscenario(leftplot)andfortheidealalignmentscenario(rightplot).Forthestart-upalignmentthetrianglepointersofthegrapharetheaveragebetweenmaximumandminimumcorrections,calculatedwiththetwomodelsofsmearingthemuonpT(theverticalerrorbarsconnecttheresultsofthetwomodels).TrianglepointersontherightplotcorrespondtothemuonpTresolutioninidealalignmentscenario.ThetwoothermodelsofsmearingthemuonpTareconnectedbytheverticalbars. 7-25 ,whichshowstheplotoftheqTspectrumshape,generatedon250pb1oftheDrell-Yanevents(minv>40GeV/c2).With10pb1of10TeVproton-protoncollisiondatawecanmeasuretheqTspectrumroughlyashighastheD0collaborationdidwith1fb1of1.96TeVproton-antiprotoncollisiondata.ThestatisticaluncertaintyinthehighestbinofqT170GeV/cisabout20%.100pb1ofdataat10TeVreachthesamelevelofstatisticaluncertaintyatqT350GeV/c. 101

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Thesoft(leftplot)andthehard(rightplot)partsoftheqTspectrumshape.Bluebottom-pointingtrianglesthecorrectedqTspectrumafterthefulldetectorsimulation(250pb1).Verticalbarsstatisticuncertainty,scaledasifweprocess100pb1ofdata(topplots)and10pb1ofdata(bottomplots).Shadedareasystematicerrorfromtheunfoldingandefciencymeasurement.Redtop-pointingtriangles:ontheleftgenerator-levelqTspectrum,ontherightNNLOspectrumofFEWZzprogram. OnMarch30,2010,theLHCacceleratorsuccessfullyreacheda7TeVcenter-of-masscollisionenergy.ForthepurposeoftheLHCmachinesafetythecollisionenergyof7TeVwillbeusedthroughtheyear2010(andlikely2011).Theexperienceaccumulatedinthe10TeVsimulationstudypreparedusfortheanalysisof2010LHCcollisiondata.WeexpecttoobtainaquicknewphysicsresultintheregionofqT,whichwasneverstudiedbefore. 102

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7 tomodelthesoftpartofthepTspectrumofZ. 103

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3MostofthenumbersinthissectionweretakendirectlyfromthePythia[ 21 ]eventgenerationprogram.4TheLHCoperatedatanoccupancyof0.01.1proton-protoncollisionsperbunchcrossing. 104

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8.2.1DataTheUnderlyingEvent(UE)isanexcellentprobeofsoftQCDphysics.Onthelevelofindividualpartons,theprocesscanbeeasilydenedasallthecollisionproductsexceptforthetwohardscatteringpartons.Thehardscatteringpartonsgeneratemultiplecollinearparticlesintheprocessofhadronization.ThestandardwaytoisolatetheseparticlesistopartitiontheeventinthespacewithrespecttothedirectionofsomehighpTobject(asingleparticleorjet)[ 40 ].Weusetheazimuthalanglewithrespecttothedirectionofthisleadingparticleorjetanddenethreeregionsasfollows(Figure 8-1 ): 37 ]. 105

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Regionsforthedataselection. Thetowardandawayregionsareexpectedtoreceivetheproductsofthehardscattering.Thetransverseregionisroughlyperpendiculartothe2-to-2hardscatteringplane.ItissensitivemainlytotheUnderlyingEvent.Thetwosectionsofthetransverseregionmaybestudiedseparately.Thesectionwithhighernumberofparticles(thetransMAXregion)islikelytoreceiveacontributionfromapossibleinitialornalstateradiation.Anothersectionofthetransverseregion(thetransMINregion)willthencontainmostlythebeam-beamremnants.MinimumBias(min-bias)dataofferanotherprospectivetostudythesoftQCDphysics[ 38 ].Thistypeofdataarecollectedwithaloosetriggerrequirement.Therequirementisdesignedtominimizetriggerbiastowardssomespeciceventsignatures.Ideally,themin-biasdatashouldcontainallthephysicsprocessesproportionaltotheirproductionrates.ItisdominatedbytheeventswithsoftQCDcollisions.Samephenomenologicalmodelsareusedtodescribeboth,underlyingeventsinhard2-to-2scatteringprocessandsoftmin-biascollisions. dd)andtransverse 106

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40 ].TherstobservableisthenumberofchargedtracksaboveacertainpT,normalizedtotheareaofthatregion.ThesecondobservableisthenormalizedscalarsumofthepTofallthetracksabovethethreshold.InbothcaseswestudythecorrelationoftheobservablewiththepToftheleadingtrack.Thetypicalproleplots(anaveragevalueoftheobservableony-axiscalculatedindifferentbinsofpToftheleadingtrackonx-axis)areshowninFigure 8-2 Thedensityofchargedparticles(left)andtransversemomentumow(right)observablesformin-biasevents.TheplotsaregeneratedwiththeD6Ttune[ 39 ]forPythia. 40 43 ].ThenewCMSresultsat900GeVarecomparedwiththepredictionsofoneofthesoftQCDmodels,previouslystudiedbyCDF. 107

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39 ].AdditionalPythiatuneswerealsousedtotestforpossibledependenceofthedetectorsimulationperformanceontheUnderlyingEventmodel. 8-1 providesdetailsonthedataselection.Eightrunswiththelargestnumberofcollectedeventswerechosenfortheanalysis.Therunacquisitiontimeisdividedindifferentluminositysectionranges.Foreachoftherunsweidentiedtheluminositysectionswithstablebeamandtrackerconditions.5Anadditionallowintensityparasiticbunchofprotonsproducedcollisions10mawayfromthenominalcollisionpoint.Werejectedthesecollisionsrequiringonlyeventscompatiblewiththepropercollidingbunchesintime. Table8-1. Datafortheanalysis Run Luminosity Collidingbunches Selectedevents(103) sections ZeroBias Minimumbias 124009 1 2824,151,51 777 1121 124020 12 2824,151,51 956 550 124022 69 2824,151,51 1032 619 124023 41 2824,151,51 615 405 124024 2 2824,151,51 933 557 124027 24 2824,151,51 176 117 124030 1 2824,151,51 310 219 124230 26 51,151,232, Not 466 1024,1123,1933, available 2014,2824,2905 Atotalof4798980ZeroBiaseventsand4054266MinimumBiaseventsareacceptedbythisselection. 108

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109

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8-2 showsthereductionofthenumberofeventsafterapplyingvarioustrigger-basedselectioncriteria.7 Totalnumberofeventsafterapplyingvarioustrigger-basedselectioncriteria. Selection ZeroBias MinimumBias Noselection 14290581 19681382 Dataselection 4798980 4054266 SingleBSChit 1459 509082 SingleBSChitandnoBSChalotrigger 1419 492893 2-stationBSCmin-biastriggers 735 263691 2-stationBSCmin-biasandnoBSChalotriggers 730 260773 BPTXcoincidenceandalltheabovetriggers 730 260772 8-3 showsthez-coordinateofthevertexinrun#124230.Itnicelytsthegaussianshapewiththe15cmwindowroughlyequaltoa3interval.Theaveragevertexpositioniscalculatedindependentlyforeachrun(Table 8-3 ).Thetracker-basedeventselectionkeeps235637min-biaseventsoutof260772eventsfromthegoodluminositysectionsandcollidingbunches,whichpassthetrigger-basedselection. 110

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Distributionofthez-coordinateforthevertexinrun#124230. Table8-3. Averagez-coordinateofthevertex. Run Averagez -0.68 124020 -0.58 124022 -0.61 124023 -0.61 124024 -0.62 124027 -0.62 124030 -0.57 124230 -1.19 111

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jd0j<(0.3nhits)4d0(pT) jd0j=d0<(0.4nhits)4 8-4 ).TheagreementbetweentherealperformanceofthedetectorandthesimulatedoneisessentialforthecomparisonbetweenthemeasureddN ddanddPsumT 8-5 demonstratesubstantialreductionofnumberofsecondaryparticleswithalittledecreaseintheefciencytotheprimaryparticles. 112

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Distributionofthetransversemomentumbefore(left)andafter(right)thecutontheuncertaintyofthetransversemomentummeasurement.ThecuthelpstocleanthesamplefromtrackwithunreliablepTmeasurement(especiallyinthehigh-pTtail)andachievebetteragreementbetweenthedataandD6TPythiasimulation. MonteCarloefciencyofthetrackselectioncutstoprimaryparticles(left)andsecondaryparticles(right).TheplotiskindlyofferedbyGiuseppeCerati. ddanddPsumT 113

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8-6 demonstratesthattheMonteCarloefciencyoftheBSCtriggerselectionagreeswellwiththeefciencyderivedfromtheZeroBiasdata.TheBPTXcoincidencetriggerisexpectedtobenearly100%efcient.Therefore,weconsidertheBPTXtriggerbiasnon-existing. EfciencyoftheBSCtriggerselectioninsimulation(threePythiatunesareshown)andindata. AMonteCarlostudy(Figure 8-7 )showsbiasfromthetrigger-basedselectiontobeontheorderof2%formostofthebinsinthedN ddanddPsumT 114

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Topplots:dN dd(left)anddPsumT 115

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8-8 .Theresultsofthecomparisonare:9 8-9 showsthechargedparticledensityandthetransversemomentumowmeasuredprolessuperimposedtothesimulationwithPythiatuneD6Tinthetoward,transverse,andawayregions.Thedatapoints,reportedintheFigure 8-9 ,arenotcorrectedforthebias,whichresultsfromlimiteddetectorefciencyandresolution.Instead,theyarecomparedtothePythiaD6TMonteCarlopredictionspropagatedthroughthefulldetectorsimulationwithsucheffects.Thesystematicuncertaintyofthesimulatedspectraisestimated 116

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Validationoftheinnertrackersimulation.Inpanels:Anumberofdegreesoffreedomofthetrackt;Bnormalizedtrackt2;C,D,Ftrack'spseudorapidity,azimuthalangle,andtransversemomentum,respectively;Epereventtrackmultiplicity.Linessimulation,dotsdata. 117

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Chargedparticledensity(left)andtransversemomentumow(right).Datadots,MonteCarlocircles.Toprowtowardregion,middlerowtransverseregion,bottomrowawayregion.Intheplotsforthetransverseregionwealsoshowsystematicuncertainty(shadedarea). byvaryingseveralparametersaffectingaccuracyofthedetectorsimulationandcomparingpredictionsforthespectra.Followingsourcesofthesystematicuncertaintyareconsidered: 118

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8-7 ).Thisiscomparabletotheabsolutemagnitudeofthetriggerbiasinallbuttherstbins.Wedonotexpectaveryhighaccuracyofthetriggersimulationintherstbin.Therefore,weadoptaconservativeestimatefortheuncertaintyofthetriggersimulationastheabsolutemagnitudeofthetriggerbias,foundinthesimulation.Thevariationofthetrackselectioncutsby10%propagatesintoanegligiblevariationof<0.5%inthenalspectra,and,therefore,isnotconsideredthereafter.TheinnertrackeralignmentuncertaintywasestimatedbycomparingaMonteCarloproductionwithidealdetectoralignmentandMonteCarloproductionwithrealisticdetectoralignmentasofDecember2009andproperbeamspotpositionasmeasuredinthedata.Bothproductionsaccountfortheknowndeadchannels.Thematerialbudgetoftheinnertrackerisbelievedtobeknownwith5%accuracylevel.Weestimatethesystematicuncertaintyofthedetectorsimulationbyvaryingthedensityofinnertrackermaterialtomatchthislevel.Theuncertaintyduetobadchannelsintheinnertrackerwasstudiedbycomparingthedetectorsimulationwithidealalignmentandcalibrationbeforeandafterapplyingmapoftheknowndeadchannel(3%total). 119

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A-1 denestheHigh-LevelTrigger(HLT)pathsforL=1032cm2s1,14TeVscenario.Therelaxeddi-muonHLTpath(HLT2MuonNonIso)yieldsapproximately1:2ratioofsignaltobackground(whichismostlyQCD).TherelaxedsinglemuonHLTpath(HLT1MuonNonIso)contains98%ofbackgroundafterskimmingprocedureisapplied.TheseresultsaresummarizedinTable A-2 TableA-1. Triggerpaths,usedforthe14TeVscenario(L=1032cm2s1).Neitherpathisprescaled. HLTpath Triggername L1seed HLTpT threshold parameter Single L1 SingleMu7 16GeV/c dxy<200m Double L1 DoubleMu3 (3,3)GeV/c dxy<200m TableA-2. Numberofeventsaftereachselectionstep.Lastcolumnrepresentsthenumberofevents,weightedfor10pb1ofdata. #ofevents Global,jj<2.1 L1 SingleMu7 HLT1MuonNonIso Weighted inCSA07 DoubleMu3 HLT2MuonNonIso total(x103) 1M 917K 904K 894K 7.4 742K 6.15 QCD+MB 43M 254K 173K 63K 371 (Gumbo/Stew) 54K 7.9K 11.6 21.5M 3.2M 3M 2.8M 73 (Chowder) 162K 23K 0.3 388K 367K 303K 1.3 (Chowder) 135K 60K 0.26 59K 55K 51K 0.6 (Chowder) 8.8K 5.1K 0.06 121

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Performanceoflast2selectionsteps:cutontheinvariantmassandthemuonisolation. #ofevents Second,jj<2.1, Invariant Eitherof isisolated areisolated 7.4K 5.1K 4.9K 4.9K 4.6K 4.6K 4.4K 4.4K 4.2K QCD+MB 371K 1.3K 394 15 0 11.6K 0.5K 142 13 0 73K 15 8 7 7 0.3K 7 4 3 0.4 126 53 48 20 260 86 37 35 17 10 2 2 2 60 9 1.8 2 2 122

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B-1 showsacceptanceforeitherandbothmuonsfromthepairtobeinjj<2.1region.Figure B-2 presentsefciencyofeitherandbothmuons,passingtheacceptancecut,tohavepT>20GeV/c. EfciencyofhigherpTmuon(redtop-pointingtriangles),lowpTmuon(bluebottom-pointingtriangles),andbothmuonsfromthepair(greendots)topassthejj<2.1cutasafunctionofqT. 123

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Topleft:scatterplotofpTofmuonversuspTofmuonpairforhigherpTmuonfromthepair.Topright:sameforlowpTmuonfromthepair.Bottom:efciencyofhigherpTmuon(redtop-pointingtriangles)andlowpTmuon(bluebottom-pointingtriangles)injj<2.1region,topasspT>20GeV/ccut(horizontallineontopplots).EfciencycurvetopassthecutbybothmuonssimultaneouslypreciselyfollowsthebluecurveforthelowpTmuonand,therefore,itisnotdisplayed. 124

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C-1 theZpeakregionofthegenerator-levelinvariantmassdistributionisindeeddominatedbythevoigtianterm.Thepicturechangesinthemisaligneddata.Theproportionofthe3ttingterms,foundbythet,isnolongervalidduetoinaccuracyofthemuonpTresolutionmodel(secondandthirdrowsinFigure C-1 ).Themodelisinaccurateandthepredictionsoftheproportionsof3ttingtermsarepure.Nevertheless,theresolution,extractedfromthismodel,isstillwithin10%%oftheMonteCarloresolution. 125

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TheresultsoftheZpeakt.Leftcolumncorrespondstothettingrangeminv2(76)GeV/c2,middlecolumnisfor(80)GeV/c2range,andrightcolumnisfor(84)GeV/c2.Firstrowshowsttingcurvesforthegenerator-leveldistributionoftheminv,secondrowisforminvsimulatedwiththeidealalignmentscenario,thirdrowisforthestartupscenario.Thethickredcurveisthevoigtiancontribution,thebluecurveisasumoftheinterferenceterm(greenthincurvebelowzero)andgammaterm(brownthinmonotonouscurveabovezero). 126

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[1] L.EvansandP.Bryant,JINST3,S08001(2008) [2] R.P.Feynman,Phys.Rev.80,440(1950) [3] S.L.Glashow,Nucl.Phys.22,579(1961) [4] S.Weinberg,Phys.Rev.Lett.19,1264(1967) [5] A.Salam,ElementaryParticleTheoryOriginallyprintedinSvartholm:ElementaryParticleTheory,ProceedingsOfTheNobelSymposiumHeld1968AtLerum,Sweden,Stockholm1968,367 [6] F.J.Hasertetal.,Phys.Lett.B46,138(1973) [7] G.Arnisonetal.,Phys.Lett.126B,398(1983) [8] P.Bagnaiaetal.,Phys.Lett.129B,130(1983) [9] M.Gell-Mann,Phys.Lett.8,214(1964) [10] J.I.FriedmanandH.W.Kendall,Ann.Rev.Nucl.Sci.22,203(1972) [11] F.E.Close,ANINTRODUCTIONTOQUARKSANDPARTONSAcademicPress/london1979,481p [12] J.J.Aubertetal.,Phys.Rev.Lett.33,1404(1974) [13] J.E.Augustinetal.,Phys.Rev.Lett.33,1406(1974) [14] M.E.PeskinandD.V.Schroeder,AnIntroductiontoquantumeldtheoryReading,USA:Addison-Wesley(1995),842p [15] K.MelnikovandF.Petriello,Phys.Ref.D74,114017(2006) [16] T.G.Rizzo,arXiv:hep-ph/0610104 [17] G.Altarelli,B.Mele,andM.Ruiz-Altaba,Z.Phys.C45,109(1989) [18] C.Amsleretal.,Phys.Lett.B667,1(2008) [19] M.Drees,AnIntroductiontoSupersymmetry(1996)arXiv:hep-ph/9611409v1 [20] T.Kaluza,Sitzungsber.Preuss.Akad.Wiss.Berlin(Math.Phys.),966(1921) [21] T.Sjostrand,S.Mrenna,andP.Skands,JHEP05,026(2006) [22] R.Adolphiet.al.,JINST0803,S08004(2008) [23] S.Dasuetal.,CERN-LHCC-2000-038(2000) [24] W.Adametal.,Eur.Phys.J.C46,605(2006) 127

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A.Afaqetal.,IEEETrans.Nucl.Sci.55,172(2008) [26] D.Acostaetal.,Nucl.Instrum.Meth.A496,64(2003) [27] TWEPP-09,proceedingsoftheTopicalWorkshoponElectronicsforParticlePhysics,Paris,France,21September2009,TWEPP-09,TopicalWorkshoponElectronicsForParticlePhysics21-25Sep2009,Paris,France [28] M.MagransdeAbrilandI.MagransdeAbril,Presentedat15thIEEERealTimeConference2007(RT07),Batavia,Illinois,29Apr4May2007. [29] CMSCollaboration,JINST5,T03002(2010) [30] CMSCollaboration,JINST5,T03001(2010) [31] CMSCollaboration,JINST5,T03021(2010) [32] W.Adametal.,JINST4,T07001(2009) [33] M.Aldayaetal.,CMSAnalysisNote2010/033(2010)CERN;tobepublishedinjournal. [34] J.Alwalletal.,JHEP09,028(2007) [35] J.Allisonetal.,IEEETrans.Nucl.Sci.53,270(2006) [40] Phys.Rev.D65,092002(2002) [37] G.L.Bayatianetal.,CERN-LHCC-2006-001(2006) [38] CMSCollaboration,JHEP1002,041(2010) [39] R.Field,DESY-PROC-2009-06,P.BartaliniandL.Fano(ed.) [40] A.Affolderetal.,Phys.Rev.D65,092002(2002) [41] D.Acosta,etal.,Phys.Rev.D70,072002(2004) [42] K.Deepak,FERMILAB-THESIS-2008-54,Dec2008.128pp. [43] S.Jindariani,Nucl.Phys.Proc.Suppl.177,190(2008) [44] T.Affolderetal.,Phys.Rev.Lett.84,845(2000) [45] V.M.Abazovetal.,Phys.Rev.Lett.100,102002(2008) [46] M.Lamont,LHCluminosityestimatesLHCPerformanceWorkshopChamonix2010;tobepublishedinproceedings [47] R.Hamberg,W.L.vanNeerven,andT.Matsuura,Nucl.Phys.B359,343(1991) 128

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M.Mangano,M.Mauro,F.Piccinini,R.Pittau,andA.D.Polosa,JHEP07,001(2003) [49] S.FrixioneandB.R.Webber,JHEP0206,029(2002) [50] M.Dobbsetal.,arXiv:hep-ph/0403100 [51] J.Pumplin,D.R.Stump,J.Huston,H.L.Lai,P.Nadolsky,andW.K.Tung,arXiv:hep-ph/0201195v3 [52] T.Lampen,N.DeFilippis,F.P.Schilling,A.Schmidt,andM.Weber,CERN-CMS-NOTE-2008-029(2008) [53] W.VerkerkeandD.Kirkby,arXiv:physics/0306116 [54] A.D.Martin,R.G.Roberts,W.J.Stirling,andR.S.Thorne,Phys.Lett.B531,216(2002) [55] D.Bourilkov,C.R.Group,andM.R.Whalley,arXiv:hep-ph/0605240 129

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KhristianAleksandrovichKotovwasbornin1977inNovosibirsk,Russia.Duringhisearlyyearinschoolhedevelopedapassionfortheastronomyandlaterforphysics.In1995hebeganhisundergraduateeducationinthedepartmentofphysicsoftheNovosibirskStateUniversity.In1998hechoosethespecializationintheparticlephysicsandjoinedtheKEDRcollaborationinBudkerInstituteofNuclearPhysics.In1999hereceivedaBachelorofScienceinphysicswithhonorsandcontinuedinithemaster'sdegreeprogram.In2001hecompletedtheprogramandreceivedamaster'sdegreewithhonors.Between2001and2004hewasagraduatestudentinBudkerInstitute.In2004heenteredthegraduateprogramintheUniversityofFloridaandjoinedtheexperimentalhighenergyphysicsgroup.TherehewasworkingunderdirectionofDr.DarinAcostaonthe3-DTrack-FinderfortheLevel-1triggeroftheCMSendcapmuonsystem.HecontributedtotheDataQualityMonitoringprojectfortheCMSendcapmuonsystemledbyDr.AndreyKorytov. 130