Measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at s=7 TeV with ATLAS

摘要

In this thesis an investigation of the ratio of the production cross section of W and Zbosons in association with one jet at LHC is performed.The cross-section ratio is measured with LHC proton-proton collision data at a center-of-mass energy of 7 TeV,collected by the ATLAS experiment in 2010,corresponding toan integrated luminosity of approximately 40 pb-1.The analysis is performed selectingW and Z bosons decaying in the muon channel.It is the first time the ratio of W and Z bosons production associated with one jetis measured at such a high center-of-mass energy,the measurement is the first one atthe LHC.This measurement constitutes a very important test of perturbative theoreticalcalculations based on the advantage of the partial and full cancellations of various uncer-tainties.It also serves as constraining backgrounds with similar topological signatures in thesearch for new physics phenomena at the LHC.The measured ratio value is presented as a function of cumulative jet transverse momentum thresholds and found,within statistical precision,to agree well with perturbativeLO and NLO QCD predictions.

目录

Contents

Acknowledgements

Abstract

Résumé

List of Figures

List of Tables

Chapter 1 Introduction

Chapter 2 The Standard Model of Particle Physics

2．1 The Standard Model of Particle Physics

2．1．1 Elementary particles of Standard Model

2．1．2 Field Content of Standard Model

2．2 Production of W/Z boson associated with jets at LHC

Chapter 3 LHC and ATLAS Experiment

3．1 Introduction of Large Hadron Collider

3．2 Introduction to the ATLAS Experiment

3．2．1 Overview of ATLAS Detector

3．2．2 Inner Detector

3．2．3 Calorimetry

3．2．4 Muon System

Chapter 4 Trigger and Data Acquisition system

4．1 Overview of ATLAS trigger system

4．2 L1 Trigger

4．3 HLT Trigger/DAQ

Chapter 5 Object Reconstruction at ATLAS

5．1 Muon

5．2 Jets

5．3 EmissT

Chapter 6 Rjets measurement

6．1 Introduction of Rjets

6．1．1 Motivation of measurement of Rjets

6．1．2 Definition of the Rjets measurement

6．1．3 Analysis strategy

6．2 Data and Monte Carlo Samples

6．3 Event Selection

6．4 Correction of Rjets

6．4．1 Electroweak Background estimation

6．4．2 QCD Background estimation

6．4．3 Muon Trigger

6．4．4 Vector Boson Acceptance

6．4．5 Correction of Jet PT Spectrum

6．4．6 Pile-up Removal and Jet-Related Uncertainty

6．5 Theoretical Prediction

6．5．1 Parton Level Predictions and Uncertainties

6．5．2 Hadronization Correction and Uncertainties

6．6 Results of Rjets

6．6．1 Rjets Measurement in Fiducial Phase Space

6．6．2 Rjets Measurement correction to Total Phase Space

Chapter 7 Conclusion

Bibliography

Appendix A Search for excited muons in proton-proton collisions with ATLAS

A．1 Introduction of (e)*

A．2 Data and Monte Carlo Samples

A．2．1 Data Collected

A．2．2 Monte Carlo Signal Samples

A．2．3 Monte Carlo Background Samples

A．3 Event Selection

A．3．1 Photon Selection

A．3．2 LAr front-end board failure

A．3．3 Photon ID efficiency

A．4 Background Estimation in Muon Channel

A．4．1 Muon identification and event selection

A．4．2 Muon efficiency

A．4．3 Momentum resolution smearing

A．4．4 Drell-Yan control sample

A．4．5 Estimating the Z+jet background

A．4．6 Background validation in control region

A．4．7 Optimizing the search region

A．4．8 Signal efficiency

A．4．9 Data and background prediction in signal enriched region

A．4．10 Z veto and final yields

A．5 Systematics Uncertainty

A．6 Setting Limits on μ*

A．6．1 Discovery statistics

A．6．2 Limits

A．6．3 Signal Templates

A．7 Conclusion

Appendix B Probing the jet energy measurement at the TeV-scale with the multi-jet balance technique with ATLAS

B．1 Introduction of the Multi-jet balance Technique

B．2 Data and Monte Carlo Samples

B．3 Jet Reconstruction and Calibration

B．4 Trigger and Event Selection

B．5 Measurement of the Multi-jet Balance

B．6 Estimate of the Systematic Uncertainty on the Multi-jet Balance

B．7 Conclusion

声明