A first measurement of the charged current DIS cross sections with longitudinally polarised electrons in the H1 experiment at HERA [Elektronische Ressource] / vorgelegt von Biljana Antunović

Antunovic, Biljana

Sujets

• Physik

Informations

• Publié par: ludwig-maximilians-universitat_munchen
• Publié le: 01 janvier 2007
• Nombre de lectures: 12
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

A First Measurement of the Charged
Current DIS Cross Sections with
Longitudinally Polarised Electrons in the
H1 Experiment at HERA
Dissertation
an der Fakultat¨ fur¨ Physik
der Ludwig-Maximilians-Universitat Munchen¨ ¨
vorgelegt von
Biljana Antunovi´c
aus Sarajevo (Bosnien)
Munchen 2007¨1. Gutachter: Prof. Dr. Christian Kiesling
2. Gutachter: Prof. Dr. Otmar Biebel
Tag der mundlic¨ hen Prufung:¨ 16. Marz¨ 2007
2Abstract
The analysis presented in this thesis is based on data from electron-proton collisions
√
with longitudinally polarised electron beams at a centre-of-mass energy of s =
319 GeV. The data were taken with the H1 detector at the HERA collider in the year
2005 corresponding to two polarisation states: a left-handed electron polarisation of
−27% and a right-handed electron polarisation of +37%, corresponding to integrated
−1 −1luminosities of 68.6pb and 29.6pb , respectively. The inclusive total deep inelastic
charged current cross section and the differential cross sections are measured for both
2 2helicities in the kinematic domain Q > 400 GeV and y<0.9.Theentireanalysis
chain necessary for the determination of the cross sections is described with emphasis
on the understanding of the performance of the Liquid Argon trigger system. The
experimental results obtained are consistent with the predictions of the Standard
Model. In particular, the measurement of the total polarised charged current cross
section confirms the Standard Model expectation that there are no weak charged
current interactions mediated by a hypothetical right-handed W boson. In addition,
cca measurement of the charged current structure function F has been performed at
2
the H1 experiment for the first time. The measurements are well described by the
theoretical expectations based on parton distributions derived from inclusive neutral
current measurements in H1, and are in agreement with published data from the
(−)
±ZEUS (e p) and CCFR (ν Fe) experiments.μKurzfassung
In dieser Arbeit wird die Analyse von der Streuung von longitudinal polarisierten
√
Elektronen an Protonen bei einer Schwerpunktsenergie von s = 319 GeV pr¨asen-
tiert. Die Daten wurden mit dem H1 Experiment am HERA Beschleuniger im Jahre
2005 aufgenommen. Sie bestehen aus zwei Datens¨atzen: linksh¨ andig polarisierte
Elektronen mit einer Polarisation von −27% und rechtsh¨ andig polarisierte Elektro-
−1nen mit einer Polarisation von 37% mit integrierten Luminosit¨ aten von 68.6pb
−1und 29.6pb . Der inklusive totale Wirkungsquerschnitt fur¨ die tief-inelastische
Streuung mit geladem Strom und die differentiellen Wirkungsquerschnitte werden
2 2f¨ur beide Helizit¨ aten in der kinematischen Region Q > 400 GeV und y<0.9
gemessen. Die gesamte Analysekette, welche fur¨ die Bestimmung der Wirkungsquer-
schnitte notwendig ist, wird beschrieben. Besonderer Wert wird auf das Verst¨ andnis
des Flus¨ sig-Argon Kalorimetertrigger-Systems gelegt. Die erhaltenen experimentellen
Resultate sind mit den Voraussagen des Standardmodells gut vertr¨ aglich. Insbeson-
dere best¨ atigt die Messung des totalen polarisierten Wirkungsquerschnitts fur¨ den
geladenen Strom die Vorhersage des Standardmodells, dass es keine schwachen Wech-
selwirkungen durch hypothetishe rechtsh¨ andige W-Bosonen gibt. Zus¨atzlich konnte
cczum ersten Mal die Strukturfunktion F f¨ur geladene Str¨ ome mit dem H1 Experi-
2
ment gemessen werden. Die Messungen stimmen mit den theoretischen Erwartungen
gut ub¨ erein, die auf den M der Partonenverteilungen mittels der inklusiven
Streuung mit neutralem Strom mit dem H1 Detektor gewonnen wurden. Sie stimmen
(−)
±auch mit publizierten Werten von ZEUS (e p) und CCFR (ν Fe)¨uberein.μContents
1 Introduction 1
2 Theoretical Overview of Charged Current Interactions 4
2.1 DepInelasticScatering.......................... 4
2.2 TheStructureofHadrons .. 6
2.3 QuarkPartonModel..... 7
2.4 ScalingViolationsandQuantumChromodynamics ........... 8
2.5 Electromagnetic Interactions of Charged Spin 1/2Fermions.......10
2.6 WeakInteractions..............................12
2.6.1 The V − ANatureoftheWeakCurents..14
2.6.2 TheWeakCouplingConstant........15
2.6.3 ElectroweakUnification ...........16
2.6.4 TheHigsMechanism.......................17
2.6.5 ParityViolationintheElectroweakModel.18
2.7 NeutralCurentCrosSectionandStructureFunctions.........20
2.8 ChargedCurentCrosSectionandStructureFunctions ........21
− +2.8.1 Comparison of the e p and e pCCCrossSections .......22
3 The HERA collider and the H1 Detector 25
3.1 The HERA collider .............................25
3.2 Luminosity ..........26
3.3 LeptonPolarisationatHERA............28
3.3.1 TranverseElectronBeamPolarisation....29
3.3.2 LongitudinalElectronBeamPolarisation.............30
3.4 TheH1Detector...................3
3.4.1 TrackingSystem ...35
3.4.2 Calorimeters......36
3.4.2.1 TheLiquidArgonCalorimeter .............37
3.4.3 TheMuonSystem ..............39
3.4.4 TheTime-of-FlightSystem..........39
3.4.5 TheLuminositySystem ...........40
3.5 TrigerSystem...................40
3.5.1 TheFirstTrigerLevel............41
III CONTENTS
3.6 TheLiquidArgonTriger.........................42
3.6.1 AnalogPartoftheLiquidArgonTriger..4
3.6.1.1 The t0Signal............44
3.6.2 DigitalPartoftheLiquidArgonTrigger..45
3.6.2.1 Addertre ........................46
3.7 TheTrackTrigerElements.47
3.7.1 TheVetoConditions.48
3.7.2 TheSecondTrigerLevel ..........49
3.8 TheThirdTriggerLevel..........................49
3.9 TheFourthTrigerLevelandEventReconstruction...........49
4 Principles of the CC Cross Section Measurement 51
4.1 TheTotalCCCrosSectionMeasurement................51
4.2 SourcesofBackground................55
4.2.1 Sources of epBackground..........55
4.2.2 Sources of non-epBackground........56
4.2.3 MonteCarloSimulation......................58
4.2.4 GenerationofDISEvents..........59
4.2.5 GenerationofBackgroundEvents......60
4.3 ElectroweakRadiativeCorrections.61
4.4 ThePseudoChargedCurentMethod...................62
5 Reconstruction of Kinematic Variables in Charged Currents 66
5.1 NeutralCurentEventsforChargedCurentDataAnalysis.......6
5.2 VertexReweightingintheMC.......................67
5.3 KinematicReconstructionMethods.........68
5.3.1 Kinematic Reconstruction Method for Charged Current Events . 68
5.3.2 Kinematic Reconstruction Methods for Neutral Current Events 69
5.4 HadronicEnergyMeasurement ......................71
5.4.1 HadronicEnergyCalibration.........73
6 LAr Triggers for Charged Current Events and their Performance 75
6.1 PhysicsMotivation:CCSubtrigers....................76
6.2 EfficienciesoftheLArTrigerElements ......76
6.3 OptimisingtheLArTrigerRates..........78
6.3.1 ProposalfortheOptimisingTriggerRatesatL1.........79
6.3.2 OptimisingTriggerRatesatL2..................81
6.4 DataQualityChecks.................82
6.4.1 InternalConsistency.82
6.4.2 Comparison of LAr Trigger to the Central Trigger Logic Readout 83
6.4.3 Comparison of LAr Trigger to the Second Trigger Level Readout 84CONTENTS III
7 Analysis of Charged Current Events 85
7.1 CCSelectionCriteria............................86
7.1.1 BasicPreselection...86
7.2 FinalCCSelectionCriteria.87
7.2.1 RunSelection.....8
7.2.1.1 RunQuality .......................8
7.2.2 PolarisationRequirement...........90
7.2.3 TrigerRequirement.............91
7.2.4 VertexRequirement..91
7.2.5 KinematicPhaseSpace.......................92
7.2.6 Rejection of epBackground.........94
7.2.7 Rejection of Non-epBackground.......97
7.2.7.1 EventTiming.97
7.2.7.2 Non-epBackgroundFinders...............98
7.3 VisualScanning....................100
7.4 FinalCCSample.......10
7.5 EfficiencyDeterminationUsingPsCCEvents....103
7.5.1 ChargedCurentTrigerEfficiencies...............103
7.5.2 BackgroundFinderandEventTimingEfficiency.........104
7.5.3 TheVertexReconstructionEfficiency....107
7.6 KinematicDistributions...............109
8 Cross Section Measurement Procedure 112
8.1 CalculationoftheTotalCCCrosSection................12
8.2 DifferentialCrosSectionExtraction........12
8.3 BinDefinition.....................113
8.4 SystematicUncertainties...115
9 Results and Interpretation 121
9.1 PolarisedChargedCurentCrosSection.................121
9.1.1 The Polarisation Dependence of the Total CC Cross Section . . 122
29.1.2 The Q DependenceofthePolarisedCCCrossSection.....125
9.1.3 The xDependenceofthePolarisedCCCrosSection......127
9.1.4 PolarisedDoubleDifferentialCCCrosSection .........128
9.2 UnpolarisedChargedCurentCrosSections...............131
29.2.1 The Q Dependence of the Unpolarised CC Cross Section . . . . 131
9.2.2 The x Depe of the Unpolarised CC Cross . . . . 134
9.2.3 TheUnpolarisedDoubleDifferentialCCCrossSection.....135
cc9.3 Extraction of the Charged Current Structure Function F .......139
2
10 Summary and Outlook 143
Appendix 145IV CONTENTS
A LAr Trigger Data Quality Checks 145
A.1TrigerReadout...............................145
A.2TriggerSimulation......145
A.3AnChargedCurrentEventintheLArtrigger...146
A.4Ntuplefort