Wboson Measurement In The Muonic Decay Channel At Forward Rapidity With AlLICE

With the beginning of the Large Hadron Collider(LHC)at CERN in 2009,a.new era in Quark-Gluon Plasma(QGP)physics has started by studying heavy-ion collisions at high ener-gies in the centre of mass frame(25 times larger than those in the RHIC collider at BNL).The LHC represents today an ideal tool to study the properties of QGP in the laboratory.ALICE(A Large Ion Collider Experiment)is the only experiment of LHC specifically designed to measure those properties.A wide variety of observables can be studied by means of the 18 sub-detectors of the ALICE apparatus,which are grouped in two main elements:the central barrel and the muon spectrometer.With the muon spectrometer,we can detect high transverse momentum muons and dimuons in order to measure open heavy flavours,quarkonia and electroweak bosons pro-duction.The high collision energies available at the LHC allow for an abundant production of hard probes,such as quarkonia,high-pT jets and vector bosons(W,Z),which are produced in ini-tial hard parton scattering processes.The latter decay before the formation of the QGP,which is a deconfined phase of Quantum ChromoDynamics(QCD)matter produced in high-energy heavy-ion collisions.Furthermore,their leptonic decay products do not interact strongly with the QGP.The electroweak bosons provide a way for benchmarking in-medium modifications to coloured probes.In Pb-Pb and p-Pb collisions,precise measurements of W-boson produc-tion can constrain the nuclear Parton Distribution Functions(nPDFs),which could be modified with respect to the nucleon due to shadowing or gluon saturation.In addition,they can be used to test the scaling of hard particle production with the number of binary nucleon-nucleon col-lisions.Especially in p-Pb collisions,the measurement of W yields at forward and backward rapidity allows us to probe the modification of nPDFs at small and large Bjorken-x,respectively.Such measurements can be benchmarked in pp collisions,where W-boson production is theoret-ically known with good precision.Also,the charge asymmetry of leptons from W-boson decays is a sensitive probe of up and down quark densities in a nucleon inside a nucleus.ALICE has already completed data taking of large data samples of pp collisions at(?)s = 7,8 and 13 TeV,p-Pb collisions at(?)5NN = 5.02 TeV and Pb-Pb collisions at(?)5NN = 2.76 and 5.02 TeV.The data samples collected in Run I(i.e.in year 2009-2013)allowed us to study the production of heavy flavours and W-boson through their muonic decay channel in pp and p-Pb collisions.The production of W-boson in pp collisions at 8 TeV and p-Pb collisions at 5.02 TeV are measured with the ALICE muon spectrometer via the inclusive pT-differential muon yield.In pp collisions the rapidity covered by muon spectrometer is-4<ycms<-2.5and in p-Pb collisions it separates into forward rapidity(p-going direction,2.03<ycms<3.53)and backward rapidity(Pb-going direction,-4.46<ycms<-2.96)via changing beam direction.These rapidity regions are complementary to the one of ATLAS(A Toroidal LHC ApparatuS,|?lab|<2.5)and CMS(Compact Muon Solenoid,|?lab|<2.4)experiments.This thesis consists of four parts.Part I is the introduction of high-energy physics and con-tains two chapters.Chapter r is a general knowledge of QCD and QGP,and Chapter 2 concen-trates on the electro weak theory and the motivation of investigating of W-boson in heavy-ion collisions.Part II presents the ALICE experiment,which involves hardware,software,the online data taking and the offline data selection.Chapter 3 shows the design of the structure including central barrel and forward muon spectrometer and Chapter 4 gives an account of data.Part III is the core content,which reveals the detail of W-boson measurement in p-Pb(Chapter 5)and pp(Chapter 6)collisions.Finally,the conclusions are drawn in part IV(Chapter 7).