Forward jet production in neutral current deep inelastic scattering with ZEUS at HERA [Elektronische Ressource] / vorgelegt von Arno Benen
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Forward jet production in neutral current deep inelastic scattering with ZEUS at HERA [Elektronische Ressource] / vorgelegt von Arno Benen

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Forward Jet Production in NeutralCurrent Deep Inelastic Scattering withZEUS at HERAINAUGURALDISSERTATIONzur Erlangung des Doktorgradesder Fakult˜at fur˜ Mathematik und PhysikderAlbert-Ludwigs-Universit˜at Freiburg i. Br.vorgelegt vonArno Benenaus Bersenbruc˜ kFreiburg i. Br.December 2003Dekan : Prof. Dr. R. SchneiderReferent: Prof. Dr. A. BambergerKoreferent : Prof. Dr. U. LandgrafTag der Verkundigung˜des Prufungsergebnisses˜ : 22.3.2004To My FatheryContentsIntroduction 81 The ZEUS Experiment at HERA 101.1 The Storage Ring HERA . . . . . . . . . . . . . . . . . . . . . 101.2 The ZEUS Detector . . . . . . . . . . . . . . . . . . . . . . . . 121.2.1 The Central Tracking Detector (CTD) . . . . . . . . . 161.2.2 The Uranium Calorimeter (UCAL) . . . . . . . . . . . 181.2.3 Presampler . . . . . . . . . . . . . . . . . . . . . . . . 191.2.4 Luminosity Monitor . . . . . . . . . . . . . . . . . . . 191.2.5 Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 The Forward Plug Calorimeter (FPC) 232.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.2 Structure and Properties . . . . . . . . . . . . . . . . . . . . . 242.3 Performance and Calibration . . . . . . . . . . . . . . . . . . . 262.4 Beam Halo Muons . . . . . . . . . . . . . . . . . . . . . . . . 303 Theory 333.1 QCD General . . . . . . . . . . . . . . . . . . . . . . . . . . . 333.2 Structure of the Proton . . . . . . . . . . . . . . . . . . . . . .

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Published 01 January 2004
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Forward Jet Production in Neutral
Current Deep Inelastic Scattering with
ZEUS at HERA
INAUGURALDISSERTATION
zur Erlangung des Doktorgrades
der Fakult˜at fur˜ Mathematik und Physik
der
Albert-Ludwigs-Universit˜at Freiburg i. Br.
vorgelegt von
Arno Benen
aus Bersenbruc˜ k
Freiburg i. Br.
December 2003Dekan : Prof. Dr. R. Schneider
Referent: Prof. Dr. A. Bamberger
Koreferent : Prof. Dr. U. Landgraf
Tag der Verkundigung˜
des Prufungsergebnisses˜ : 22.3.2004To My FatheryContents
Introduction 8
1 The ZEUS Experiment at HERA 10
1.1 The Storage Ring HERA . . . . . . . . . . . . . . . . . . . . . 10
1.2 The ZEUS Detector . . . . . . . . . . . . . . . . . . . . . . . . 12
1.2.1 The Central Tracking Detector (CTD) . . . . . . . . . 16
1.2.2 The Uranium Calorimeter (UCAL) . . . . . . . . . . . 18
1.2.3 Presampler . . . . . . . . . . . . . . . . . . . . . . . . 19
1.2.4 Luminosity Monitor . . . . . . . . . . . . . . . . . . . 19
1.2.5 Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2 The Forward Plug Calorimeter (FPC) 23
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2 Structure and Properties . . . . . . . . . . . . . . . . . . . . . 24
2.3 Performance and Calibration . . . . . . . . . . . . . . . . . . . 26
2.4 Beam Halo Muons . . . . . . . . . . . . . . . . . . . . . . . . 30
3 Theory 33
3.1 QCD General . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.2 Structure of the Proton . . . . . . . . . . . . . . . . . . . . . . 34
3.2.1 The Naive Quark Parton Model . . . . . . . . . . . . . 36
3.2.2 The QCD Improved Quark Parton Model. . . . . . . . 38
3.3 Evolution Equations . . . . . . . . . . . . . . . . . . . . . . . 39
3.3.1 DGLAP Evolution . . . . . . . . . . . . . . . . . . . . 40
3.3.2 BFKL Ev . . . . . . . . . . . . . . . . . . . . . 42
3.3.3 CCFM Evolution . . . . . . . . . . . . . . . . . . . . . 44
3.4 Forward jets as a signature of BFKL . . . . . . . . . . . . . . 45
4 Kinematic Variables 49
4.1 Deflnition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.2 Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . 50
14.2.1 Electron Method . . . . . . . . . . . . . . . . . . . . . 50
4.2.2 Jacquet-Blondel Method . . . . . . . . . . . . . . . . . 52
4.2.3 Double-Angle Method . . . . . . . . . . . . . . . . . . 53
5 Jet Production 55
5.1 Jets in QCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.2 Jet Observables . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.3 The Inclusive k Algorithm . . . . . . . . . . . . . . . . . . . 58?
5.4 The Breit Frame . . . . . . . . . . . . . . . . . . . . . . . . . 59
6 Monte Carlo Simulation 63
6.1 Monte Carlo in General . . . . . . . . . . . . . . . . . . . . . 63
6.2 Parton Evolution Models . . . . . . . . . . . . . . . . . . . . . 64
6.2.1 Matrix Elements . . . . . . . . . . . . . . . . . . . . . 65
6.2.2 Parton Shower . . . . . . . . . . . . . . . . . . . . . . 66
6.2.3 Colour Dipole Model . . . . . . . . . . . . . . . . . . . 66
6.3 Hadronisation Phase . . . . . . . . . . . . . . . . . . . . . . . 68
6.3.1 Lund String Model . . . . . . . . . . . . . . . . . . . . 68
6.3.2 Cluster Fragmentation . . . . . . . . . . . . . . . . . . 69
6.3.3 Soft Colour Interaction . . . . . . . . . . . . . . . . . . 70
6.4 QED Corrections . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.5 Event Generators and Interfaces . . . . . . . . . . . . . . . . . 71
6.5.1 LEPTO . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.5.2 ARIADNE . . . . . . . . . . . . . . . . . . . . . . . . . 72
6.5.3 DJANGO and HERACLES . . . . . . . . . . . . . . . 72
6.5.4 JETSET . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7 Event Selection 74
7.1 Data Taking and Reconstruction . . . . . . . . . . . . . . . . 74
7.1.1 Basic Trigger Requirements . . . . . . . . . . . . . . . 74
7.1.2 Calorimeter Noise Suppression . . . . . . . . . . . . . . 75
7.1.3 Beam-Gas Interactions . . . . . . . . . . . . . . . . . . 75
7.2 Scattered Lepton Reconstruction . . . . . . . . . . . . . . . . 76
7.3 Preselection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
7.4 Cleaning Cuts . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
7.5 Kinematic Region . . . . . . . . . . . . . . . . . . . . . . . . . 79
7.6 Jet Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
8 The Analysis 86
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
8.2 Comparison of Data and Monte Carlo . . . . . . . . . . . . . . 87
28.3 Jet Energy Correction . . . . . . . . . . . . . . . . . . . . . . 91
8.4 Resolution of the Observables . . . . . . . . . . . . . . . . . . 95
8.5 Jet Proflles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
8.6 Jet Observables . . . . . . . . . . . . . . . . . . . . . . . . . . 101
8.7 Purities, E–ciencies and Acceptance Corrections . . . . . . . . 106
8.8 Systematic Studies . . . . . . . . . . . . . . . . . . . . . . . . 113
8.9 Forward Jet Cross Sections . . . . . . . . . . . . . . . . . . . . 119
8.10 Comparison to the other measurements . . . . . . . . . . . . . 119
Conclusion 122
Appendix 123
Acknowledgements 130
3List of Figures
1.1 Picture of the HERA accelerator . . . . . . . . . . . . . . . . 11
1.2 HERA luminosity . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.3 The HERA accelerator . . . . . . . . . . . . . . . . . . . . . . 13
1.4 Side view of the ZEUS detector . . . . . . . . . . . . . . . . . 15
1.5 View of the ZEUS detector along the beam line . . . . . . . . 16
1.6 CTD octant . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.7 FCAL module . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.8 LUMI System . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
1.9 The ZEUS trigger system . . . . . . . . . . . . . . . . . . . . 22
2.1 FPC embedded in ZEUS . . . . . . . . . . . . . . . . . . . . . 23
2.2 FPC picture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3 Structure of the FPC . . . . . . . . . . . . . . . . . . . . . . . 25
2.4 Side view of the FPC . . . . . . . . . . . . . . . . . . . . . . . 26
2.5 Electron energy resolution of the FPC . . . . . . . . . . . . . 27
¡2.6 Energy measured for … in the HAC section of FPC . . . . . . 28
2.7 The reconstructed energy measured in the HAC sections of
the FPC for 100 GeV muons . . . . . . . . . . . . . . . . . . . 29
2.8 Energy distribution within the FPC HAC of beam halo muons 31
2.9 Mean peak energies for outer and inner cells of the FPC . . . 32
3.1 Kinematics of a deep inelastic scattering event . . . . . . . . . 34
23.2 The NC and CC cross sections as a function of Q measured
at HERA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.3 Schematic diagram of scaling violation . . . . . . . . . . . . . 37
em 23.4 F vs: Q for flxed x . . . . . . . . . . . . . . . . . . . . . . 392
3.5 Diagrams corresponding to the splitting functions . . . . . . . 41
3.6 The DGLAP gluon cascade . . . . . . . . . . . . . . . . . . . 42
3.7 The BFKL gluon cascade . . . . . . . . . . . . . . . . . . . . . 43
3.8 Schematic representation of the applicability of various evolu-
2tion equations across the (x,Q ) plane. . . . . . . . . . . . . . 46
4