Precision Measurements Of The Effective Weak-Mixing Angle And The Transverse Momentum Distribution Of W Bosons On Hadron Colliders

This thesis reported the precision measurement of the weak-mixing angle and the measurement of the transverse momentum of W bosons with the events recorded by D0 detector at Tevatron and the study of the high precision electron calibration method with the events recorded by ATLAS detector at LHC.These three studies are deeply correlated in physics and experimental technique.The weak-mixing angle is one of the fundamental parameters in the electroweak theory.Other standard model particles or new physics particles can participate the weak interaction through high order loops,therefore affect the measured value of the weakmixing angle.So the measurement of the weak-mixing angle is not only a precise test of the standard model but also an indirect search of the new physics particles.Before the work described in this thesis started,the weak-mixing angle had been measured with the electron channel data at Tevatron,but the high precision muon channel result is in the long-term absence at Tevatron.On the one hand,the comparison between the electron channel result and the muon channel result is an important part of the test of the standard model,on the other hand,due to the charge dependence of the muon momentum calibration,the systematic uncertainty of the muon channel could not be effectively controlled.In this thesis,a new muon momentum calibration method is designed to suppress this systematic uncertainty to a relative negligible level.On this basis,the muon channel measurement of the weak-mixing angle was carried out,which covered the blank of the high precision muon channel measurement of the weak-mixing angle at Tevatron and which is still on the highest precision level of the muon channel results.The combination of the measurements of the weak-mixing angle at Tevatron is also described in this thesis.In this work,the correlation of the uncertainties among different measurements was discussed in details and the final result of the weak-mixing angle at Tevatron was also provided,which reached the precision of one part per thousand equivalent to the measurements from LEP and SLD.After this,the precision electroweak measurements were moving to LHC.However,the precision measurements at LHC have fundamental difference to those at Tevatron.First,after the discovery of the Higgs boson,the focus of the precision measurement of the weeak-mixing angel was changed from observing the effect from the high order loops to the direct comparison between the experimental result and the prediction.At the moment,the precision of the electroweak prediction has been increased to one part per ten thousand level.In order to make the precision of the measurement comparable to that of the prediction,the goal of the precision of the weak-mixing angle measurement at LHC should be correspondingly increased to one part per ten thousand level.Second,due to the increase of the luminosity and the energy,it will be the first time that the precision is dominated by the systematic uncertainty.This will lead to the effect which was ignored at Tevatron due to the relatively large statistical uncertainty becoming the dominate effect at LHC and the data analysis procedure designed for the statistical uncertainty dominated situation needing redesigned.First,from the early measurements of the weak-mixing angle at LHC.the uncertainty due to the non-perturbative QCD effect which was ignored at Tevatron will become one of the limiting factors of the weak-mixing angle measurement.In order to constrain the non-perturbative QCD calculation,in this thesis,the spectrum of the transverse momentum of W bosons was precisely measured with the data of D0 experiment.This measurement not only provided important physics results for the non-perturbative QCD but also had innovations on the analysis procedure.In order to avoid the significant precision reduction due to the unfolding procedure under the systematic uncertainty dominated condition,a folding method was provided for future comparisons between the data and other predictions instead of the unfolding procedure,which made this measurement the one providing the physics result without unfolding since these years.Second,the dominate experimental systematic uncertainty of the weak-mixing angle measurement,the uncertainty due to the lepton calibration,will also become one of the limiting factors at LHC due to the reduction of the statistical uncertainty.At the same time,due to the limited precision of the calibration method previously designed for the statistical uncertainty dominated situation,a new lepton calibration method needed to be developed at LHC.So in this thesis,the study of the electron energy calibration method for ATLAS experiment is described and a new complete electron calibration technique is provided which increased the precision of the electron energy measurement on ATLAS experiment more than one order of magnitude and laid the foundation of the precision electroweak measurements on ATLAS experiment.At the moment,this method has been accepted by the ATLAS collaboration and became the standard calibration method which providing high precision calibration results for all the electron related measurements on ATLAS experiment.