| Currently,the nucleus has been an important subject studied in high energy experiments.In high energy nuclear experiments,nuclear parton distribution functions are the important input information to calculate/simulate various high energy reactions,playing a vital role in testing the Standard Model and searching for the new physics signals.The aim of this thesis is to obtain parton distribution functions of proton and nuclei,by a QCD analysis of l-p/A deeply inelastic scattering data worldwide.We have released the proton parton distribution functions called IMParton16,and the nuclear parton distribution functions called n IMParton16(shorted for nuclear IMParton).This work contains three main topics.(1)the origin of partons inside nucleon is studied.We have successfully constructed a direct connection between the quark model and the parton distributions measured at high Q~2.(2)modifications of parton distributions inside nucleon by various nuclear medium effects and the nuclear dependence of these nuclear effects are studied.(3)we have performed a global ?~2analysis to experimental data from different groups by using DGLAP equations with parton-parton recombination corrections,and acquired the proton and nuclear parton distribution functions.On the origin of parton distributions,we developed the dynamical parton model,and extended the initial evolution scale down to Q~20? 0.1 Ge V~2.At this input scale,we have realized the simplest and naive nonperturbative input consisting of only valence quarks,and have the fewest free parameters for parametrization,which is of only three.It is also found that there should be a few nonperturbative sea quark components beyond the quark model inside nucleons.About the nuclear medium effects,we have systematically studied the nucleon Fermi motion smearing effect to the nuclear structure function,the EMC effect generated from the nucleon swelling,and nuclear shadowing effect resulted from parton-parton recombination enhancement in nuclei.On the EMC effect,we discovered an amazing linear correlation between the strength of the EMC effect and the residual strong interaction energy among nucleons,for the first time.Nuclear shadowing effect,anti-shadowing effect,and the EMC effect are all calculated at the parton level.Based on a comprehensive consideration of nuclear effects,the determined nuclear parton distributions are more reliable,and the fewest free parameters are used to describe the x-dependence and nuclear dependence of nuclear modification factor,which is of only two(the number of free parameters is almost one order of magnitude fewer,compared to other global analyses).For the QCD global analysis of parton distributions,we are the first to apply DGLAP equations with parton-parton recombination corrections,which is a powerful tool.This is an important innovation of the work.The physical meaning of the results in this work is threefold.(1)we have successfully realized a nonperturbative input without gluon distribution.This is an important development of the dynamical parton model,and bridges directly the quark model and the measurements of hard processes as well.(2)various nuclear physics models are adopted to parameterize the initial nuclear parton distributions,and the nuclear dependence of these nuclear medium effects are studied.The constraints by various nuclear models improve the predicting power for unmeasured nuclei and for distributions in unmeasured kinematic region.(3)We have obtained proton and nuclear parton distribution functions,which will have broad applications in simulations of high energy scattering processes with proton or nucleus involved.Parton-parton recombination correction is one important higher twist correction,which is nontrivial in low Q~2 or small x range.Our parton distribution functions are expected to have good predicting power in low Q~2 or small x region. |
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