The Study On The Spin Structure Of Nucleons Within TMD Factorization

The spin of hadrons and the non-perturbative Quantum Chromodynamics(QCD)are the important topics in current QCD spin physics,in which the investigation on the spin-related physical observables in high energy scattering processes can serve as the precious approach,within the factorization theorem as an important theoretical tool.Based on the factorization theorem,the physical observables can be separated into two parts:the short distance part,which can be calculated by perturbative QCD,and the long distance part,which is usually obtained by phenomenological extraction from experimental data.In this paper,the later one corresponds to the distribution functions and fragmentation functions.And in this thesis,we explore the origin of the spin-related physical observables from those phenomenological functions,and their implication to the spin structure of hadrons and quark transverse momentum,within the transverse momentum dependent(TMD)factorization including evolution effects.The main content of the thesis are organized as follows:1.We investigate the single transverse-spin asymmetry with a sin(2φ-φS)modulation in the pion induced Drell-Yan process within the theoretical framework of the TMD factorization.Since the asymmetry is contributed by the convolution of the Boer-Mulders function h1⊥ and the transversity h1,the transversity h1 can serve as a " spin analyzer" to access the Boer-Mulders function h1⊥ which represents the transversely polarization of quarks inside an unpolarized hadron.Using the model results for h1⊥ and the available parametrization for h1,and considering the TMD evolution effect of the parton distribution functions by including the Sudakov form factors,we numerically estimate the sin(2φ-φS)asymmetry at the kinematics of COMPASS.For comparison,we apply two different nonperturbative TMD evolution formalism associated with the distribution functions of the proton and the pion and two different model result associated with the distribution functions of the pion.we find that the asymmetry is sensitive to the choice of the pion distribution function,while different choice of the TMD evolution formalism will only on the nonperturbative TMD evolution only affect the shape of the q⊥-dependent of the asymmetry.We also find that the sin(2φ-φS)asymmetry as functions of xp,xπ,xF and q⊥ is sizable and qualitatively consistent with the recent COMPASS measurement in both sign and magnitude.Furthermore,our study may provide a framework to access the Boer-Mulders function of the pion and the corresponding nonperturbative TMD evolution formalism through transversely polarized πp data.2.We investigate the transverse polarization of the 1 hyperon in the processes e+e-→Λ↑π±X and e+e-→Λ↑K±X within the framework of the TMD factorization.The transverse polarization is contributed by the convolution of the transversely polarizing fragmentation function(PFF)D1T⊥ of the lambda hyperon and the unpolarized fragmentation function D1 of pion/kaon.We adopt the spectator diquark model result for D1T⊥,and considering the TMD evolution effect of the fragmentation functions by including the Sudakov form factors,to numerically estimate the transverse polarization in e+e-→Λ↑hX process at the kinematical region of Belle Collaboration.For comparison,we apply two different nonperturbative TMD evolution formalism associated with the fragmentation functions of the Λ,pion and kaon.It is found that our prediction on the polarization in the Λπ+ production and Λπ-is consistent with the recent Belle measurement in size and sign,while the model predictions on the polarizations in Λπ-and ΛK+ productions show strong disagreement with the Belle data.A comparison with our model input for the PFF with the available parameterizations indicates that a positive D1T⊥Λ/u,negative D1T⊥Λ/d and sizable sea PFF are essential to describe the many aspects of the Belle data.Possible improvements of the model calculation include allocating substantial SU(6)breaking effect to lead to a opposite sign of the u quark PFF compared with the d quark PFF,incorporating the sea quarks in the model,and taking into the Y-term in the large momentum region.3.We investigate the sin(φΛ-φS)single-spin asymmetry in the transversely polarized Λproduction in semi-inclusive deeply inelastic scattering process within the framework of the transverse momentum dependent(TMD)factorization.The asymmetry is contributed by the convolution of the polarizing TMD fragmentation function D1T⊥ of the Λ hyperon and the unpolarized TMD distribution function f1 of the proton target.We adopt the spectator diquark model result(Set Ⅰ)and the available parametrization(set Ⅱ)for,D1T⊥,Λ↑/q,and considering the TMD evolution effect of the parton distribution functions and the fragmentation functions by including the Sudakov form factors,to numerically estimate the sin(φΛ-φS)asymmetry at the kinematical region of electron ion collider(EIC).For comparison,we apply two different nonperturbative TMD evolution formalism associated with the distribution function of the proton and the fragmentation function of the Λ.It is found that the spectator di quark model result(Set Ⅰ)and the parameterized result(set Ⅱ)of D1T⊥,Λ↑/q lead to different sink(φΛ-φS)asymmetry,particularly in sign.We also discuss the impact of the assumptions and approximations applied in the calculations,which may bring large uncertainties to the results in EIC.Future measurements on the sin(φΛ-φS)asymmetry with high precision at EIC can provide important cross check on the availableΛ polarizing fragmentation functions as well as constrain them more stringently.