The Quark Transport Coefficient In The Cold Nuclear Matter

A special form of matter at extreme conditions of temperature and density existed in the early universe:the Quark-Gluon Plasma,which consisting of deconfined quarks and gluons.The extreme conditions for QGP formation can be formed in the Relativistic Heavy-Ion Collision.One of the evidences of QGP formation in the high energy collision is“jet quenching”,i.e.the parton have suffered energy loss when propagate in the dense matter produced in the reaction since the interactions between parton and medium.Studying deeply the parton propagation mechanism can help us to reveal precious information about the transport and thermodynamical properties of the QGP.However,the mechanisms by which the traversing partons lose energy to,and interact with the QGP,are still not fully understood.The cold nuclear matter is an ideal environment for the study of the parton energy loss.The lepton-nucleus semi-inclusive deep inelastic scattering and the nuclear Drell-Yan process provide an excellent place to study the energy loss effect of the final state parton and the initial state parton in the cold nuclear matter,respectively.This thesis contains two major parts:We study the energy loss effect in the lepton-nucleus semi-inclusive deep inelastic scattering process.We sort out the HERMES charged pions production data with the quark hadronization occurring outside the nucleus.By means of the analytic parameterization on BDMPS quenching weight with the target nuclear geometry effect,the leading order calculation of the hadron multiplicity ratio has been done,and compare with the selected experimental data.The relation is discovered between the unmeasurable Bjorken variable in quark transport coefficient and the measurable Bjorken variable in deep inelastic scattering.Four models are provided on the quark transport coefficient (?).The constant model,the power-law model and the double power-law model can be ruled out since the experimental fact from HERMES that the transverse momentum broadening increases as a function of the photon virtuality Q².The quark transport coefficient (?) is determined as a function of Bjorken variable x and scale Q².The trend of (?) is qualitatively in partial agreement with HERMES data on transverse momentum broadening.We study the energy loss effect in the nuclear Drell-Yan process.By means of the HKM nuclear parton distribution and the analytic parameterization on BDMPS quenching weight,the calculations of the nuclear Drell-Yan differential cross section as a function of Feynman variable x_F are performed and compared with the experimental data from Fermilab E906 and E866 Collaborations.We found that only the nuclear effects of parton distribution cannot explain the employed experimental data.Apart from the nuclear effects of parton distribution,there is the incoming quark energy loss effect in nuclear Drell-Yan process.With the nuclear geometry effect on nuclear Drell-Yan process and the quark transport coefficient as a constant,our predictions are in agreement with the experimental measurements.It is found that the nuclear geometry effect has a significant impact on the quark transport coefficient in cold nuclear matter.It is necessary to consider the detailed nuclear geometry in studying the nuclear Drell-Yan process.Our calculated results reveal that the difference in values of quark transport coefficient exists from E906 and E866 experiments.However,confirming the conclusion that the quark transport coefficient depends on the target-quark momentum fraction,still needs more accurate experimental data on the Drell-Yan differential cross section ratio in the future.The relation is discovered between the unmeasurable Bjorken variable in quark transport coefficient and the measurable target-quark momentum fraction in nuclear Drell-Yan process.Three models are proposed and discussed for the quark transport coefficient as a function of the measurable kinematic variables:the power-law model,the double power-law model and the evolution model.As for the evolution model,the quark transport coefficient is determined as a function of the Bjorken variable x₂ and scale Q².