| A hot and dense,strongly interacting novel nuclear matter is created in high energy nucleus-nucleus collision experiments conducted at the Relativistic Heavy Ion Collider(RHIC)in Brookhaven National Laboratory(BNL)Unite States,and at the Large Hadron Collider(LHC)in the European Center for Nuclear Research(CERN),known as the Quark-Gluon Plasma(QGP).This nuclear matter is closely related to the early stages of the universe,and has a profound influence on the formation and properties of stars,the microscopic structure and interaction of matters,etc..Therefore,the theoretical and experimental research of this novel QGP matter is an important research field in the frontier of high energy nuclear physics.When high energy partonic jet produced by the early hard scattering process of high energy nuclear collision traverses through this super hot and highly dense medium,strong interaction occurs between the high energy jet and the component particles of the medium,which induces gluon radiation and leads to the energy loss effect and the transverse momen-tum broadening effect of the jet,which is known as the Jet Quenching phenomenon.Jet quenching not only will it cause a suppression of the production yield of large momentum hadrons or jets,but it will also cause a change of the azimuthal correlation or the transverse momentum correlation of the jet.This study is based on the Sudakov resummation improved perturbative quantum-chromodynamics(pQCD)parton model and BDMPS jet quenching formalism,together with the space time evolution of the QGP by hydrodynamical model,using jet azimuthal angular correlation and transverse momentum correlation on the strong interactions in high energy nuclear collisions to perform tomographic research on jet transport properties in the QGP.Theoretical research shows that the energy loss of the jet is propor-tional to the transport coefficient of the jet,of which the transport coefficient is the average of the square of the transverse momentum broadening per unit length caused by multiple scatterings of the jet.We begin by exploring the azimuthal angular correlation of di-hadron,hadron-jet and dijet to study the transverse momentum broadening effect.In proton-proton(pp)collisions,the dijet azimuthal angular distribution calculated using pQCD expansion on the strong running coupling,will have large Sudakov type logarithmic terms appearing in every order of the expansion,causing the distribution to diverge near the back-to-back region,which will not be able to describe dihadron and hadron-jet data near the back-to-back region.We then applied the Sudakov resummation technique,taking into account the contributions from vacuum soft gluon radiations,to cancel the divergences appearing in the back-to-back region of the azimuthal distribution.In nucleus-nucleus(AA)collisions,the dijet azimuthal correlation will have the existing Sudakov efect,but also the transverse momentum effect cause by the medium induced gluon radiations when the jet traverses through the QGP,and this medium effects can simply be added over the Sudakov effects.Base on the pQCD parton model and BDMPS jet quenching model,we calculated and compared dihadron,hadron-jet and dijet azimuthal correlations in pp and AA collisions.Numerical analysis shows that,at RHIC kinematics the medium induced transverse momentum broadening effect in AA collisions resulted in decorrelation in the azimuthal distribution;while at the LHC energy scale,no visible angular decorrelation is observed in AA collisions,due to the fact that the medium transverse broadening effect is much weaker than the existing Sudakov effect.Since the jet energy loss is directly proportional to the jet transport coefficient,we have extracted the jet transport coefficient through the BDMPS jet quenching model.We then study the momentum asymmetry phenomena using the dijet and isolated-photon triggered jet correlation in high energy AA collisions.We first point out a textbook conclusion for dijet transverse momentum correlations in AA collisions:due to transverse momentum conservation,the lower bound for the dijet momentum asymmetry distribution calculated from pQCD for n final state particles is xJ?1/(n-1).Base on the calculation of pQCD expansion and Sudakov resummation,next-to-leading order(NLO)pQCD contribution is indispensable to describe the experimental data,while Sudakov resummation becomes im-portant to cancel the divergences near the back-to-back region.In our study of the dijet and photon-jet momentum asymmetry distribution,we applied high order pQCD to calcu-late non back-to-back phase-space regions,while using Sudakov resummation to calculate the back-to-back region,and were able produce the dijet and photon-jet transverse momentum asymmetry distribution,which could nicely describe the related experimental data.Together with the BDMPS energy loss mechanism and the space-time evolution of the QGP using 2+1 dimension hydrodynamic model,we have analysed the transport properties of the jet in QGP.Finally we investigate the jet quenching phenomenon with the azimuthal angular cor-relation and momentum correlation of heavy boson tagged jet and hadrons.Since Z and Higgs(H)heavy bosons does not participate in strong interactions,the momentum of heavy neutral boson tagged jets are given by these bosons,and because heavy bosons have a much cleaner production mechanism than photons,Z(H)tagged jets or hadrons is another type of"golden probe" which can provide a much clear understanding of jet quenching.Base on the resummation improved pQCD model,using BDMPS energy loss mechanism together with the Ohio-State University(OSU)hydrodynamics model to simulate the QGP medium,we calculated the Z-jet momentum imbalance distribution in both pp and AA collisions,with consistent result to the experimental data,and extracted the value of the transport coeffi-cient.We have also made calculations on the H-jet momentum imbalance distribution,and numerical analysis showed that,due to Higgs being heavier than Z,H-jet have a stronger Sudakov effect than Z-jet,causing more soft gluon radiations.the study ends with a theo-retical prediction calculation that could compared with the so-called unfolded experimental data,and we expect a more precise extraction of the transport coefficient.Jet transverse momentum broadening and jet energy loss,is two sides of the same coin to jet quenching phenomenon.Our study emphasize on the jet transverse momentum broadening and jet tomographic research,is an important means to study the jet transport properties.We also emphasize on the jet energy loss that causes jet and hadron yield suppression,which is an important supplementation and development in jet quenching studies.We hope to provide a complete exploration of the transport properties of the Quark-Gluon Plasma by combining both sides in our study. |
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