Medium Modifications Of Jet Observables In High Energy Heavy-ion Collisions

Two important features of the foundamental theory of strong interaction(Quantum chromodynamics)are color confinement and asymptotic freedom.Due to color confine-ment we can not observe free quark and gluon in natural conditions.Asymptotic freedom tells quarks and gluons interact weakly at high energy scale.It is then predicted that at extremely high temperature and energy density,a new kind of matter(QGP)with de-confined quarks and gluons may be formed.QGP is also excepted to be existed at very early stage of the big bang,and also in some neutron stars,as well as during relativistic heavy-ion collisions.The major purpose of high energy heavy-ion collisions performed at RHIC and LHC is to mapping the properties of QGP.Medium alteration of jet observables with high transverse momentum are widely accepted as excellent probe to investigete the properties of QGP.In the thesis,we investigate nuclear modifications,of jet observables within the same analysis framework in high energy heavy-ion collisions.Compared with jet production in proton-proton collisions,when we study jet observ-ables in heavy-ion collisions,both initial state cold nuclear matter effects and final state hot QCD medium effects should be taken into consideration.To provide cleaner baseline for jet quenching effect,by using the recent spatially dependent nuclear PDF set EPS09s,we study the cold nuclear matter modification factor for the production of leading hadrons and full jets from central to peripheral proton-nuclei collisions.It is shown that in more peripheral collisions,the cold nuclear modifications become weaker.Jet shape gives the internal energy distribution of a jet and its alteration in heavy-ion collisions relative to hadron-hadron reactions.we investigate the medium modiffcation of differential jet shapes in heavy-ion collisions within the framework of QCD resumma-tion at NLO for pp baseline and PYQUEN parton energy loss model with 3+1D ideal hydrodynamic in AA collisions.The angular distribution of medium induced gluon radi-ation is directly related to the medium correction of jet shapes,providing an approach to discriminate the angular spectra of medium induced gluon radiation from many models.Compared with CMS data,we found that the angular distributions of radiated gluon tend to be dN9/dθ∝ 1(?).This pattern of medium induced gluon radiation is also used in the flowing research.Besides,we give the predictions on nuclear modifications of jet shape and the production of single inclusive jet with different cone sizes,as well as the production of W boson tagged jet at at very high heavy-ion colliding energies.It is observed that the double differential cross section of W boson tagged jet production is enhanced at low pT region but supressed at high pT region.Furthermore,with the jet product in pp collisions by pythia6+FastJet,and parton energy loss in the frame work of PYQUEN model with 3+1D ideal hydrodynamical evo-lution of the fireball,we give the first prediction on the average value of the jet charge distribution for the leading jet in heavy-ion collision at the LHC energy.Our results show that the averaged jet charge is significant modified in A+A collisions relative to that in p + p.The different features of quark jet charge and gluon jet charge in heavy-ion collisions,and the sensitivity of jet charge modifications to flavour dependence of energy loss are observed,which could then be used to discriminate quark and gluon jet as well as their energy loss patterns in heavy-ion collisions.