Energy Loss And Nuclear Geometry Effect In Semi-inclusive Deep Inelastic Scattering

In-depth study of quark propagation and hadronization processes in cold nuclear matter can help us to understand quark-gluon plasma and its space-time evolution process. In the hadron production from semi-inclusive lepton-nucleus deep inelastic scattering, a virtual photon from the incident lepton is absorbed by a quark within a nucleus, the colored quark propagates over some distance through the nuclear medium, the existence of a degree of energy loss caused by multiple collision and soft gluon bremsstrahlung, evolves subsequently into an observed final hadron. Therefore, the hadron production from semi-inclusive lepton-nucleus deep inelastic scattering provide ideal enviorment for studying proton propagation and hadronization processes in cold nuclear matter. If quark hadronization occurring outside the nucleus, the hadron production from semi-inclusive lepton-nucleus deep inelastic scattering is a good tool to investigate the energy loss effect of outgoing quark in cold nuclear matter.In this thesis, by means of the expressions of hadron formation time from HERMES collaboration, with the hadron formation time greater than the diameter of the target nucleus as the standard, the experimental data with quark hadronization occurring outside the nucleus are picked out from the experimental results reported by HERMES collaboration on the hadron multiplicity ratios for positively charged pions production on neon nucleus and deuterium target struck by lepton. By means of the SW quenching weights and the analytic parameterizations based on BDMPS quenching weights, the computations for hadron multiplicity ratios in semi-inclusive deep inelastic scattering are presented and compared with the experimental data for the hadronization occurring outside the nucleus. It is found that the calculational results with the nuclear geometry effect in hadron production process are in good agreement with the experimental data. Considering the nuclear geometry effect, the transport parameter from the global fit with experimental data is shown to be q= 0.74±0.03 GeV2/fm for the SW quenching weight without the finite energy corrections. But the transport parameter is shown to be q=1.15±0.03 GeV2/fm without considering the nuclear geometry effect. As for the BDMPS quenching weight without the quark energy E dependence, the computed transport coefficient is q= 0.20±0.02 GeV2/fm considering the nuclear geometry effect, the computed transport coefficient is q=0.29±0.03 GeV2/fm without considering the nuclear geometry effect. Obviously the nuclear geometry effect has a significant impact on the transport coefficient (hence the quark energy loss) in cold nuclear matter. So, it is necessary to consider the nuclear geometry effect in studying the hadron production from semi-inclusive lepton-nucleus deep inelastic scattering.