The Polarization Effects Of The Dihadron Production

The spin structure of hadron is one of the hot topics in quantum chromodynamics(QCD).Studying this issue will help us to understand the internal spin structure of nucleons and further understand QCD theory.In hadronic energy scale,the QCD coupling constant will be large,It is impossible for us to do perturbation calculation directly,then the QCD factorization scheme is developed.One divides the differential scattering cross section into two parts,one is the hard scattering process,which can be calculated by perturbation,the other is the non-perturbation process,which is described by distribution function and fragmentation function.An impor-tant channel to describe the spin physics is to obtain the polarized differential scattering cross sections.The spin polarization asymmetries are given by the radio of the polarized differen-tial scattering cross sections to the non-polarized differential scattering cross sections.Spin polarization asymmetry is a powerful tool for studying hadron spin physics,which is a bridge between theory and experiment.In recent years,a series of spin asymmetries in dihadron pro-duction processes has been measured by high energy scattering experiments.Based on these experimental results,from the theoretical and phenomenological point of view,we have studied the spin polarization asymmetry of dihadron production in semi-inclusive deep inelastic scat-tering process(SIDIS).Using the spectator model,we studied the twist-3 inteference dihadron fragmentation functions,and given the numerical estimate for spin asymmetrise,especially the longitudinal asymmetry.The main content of the thesis are organized as follows:First,we study the single longitudinal-spin asymmetry of dihadron production in semi-inclusive deep inelastic scattering process.We consider the collinear picture in which the trans-verse momentum of the final-state hadron pair is integrated out,such that the sin ?R azimuthal asymmetry arises from the coupling hL H1(?)as well as the coupling g1 (?).We calculate the un-known twist-3 dihadron fragmentation function (?)using a spectator model which is successful in describing the dihadron production in the unpolarized process.Using the spectator model results for the quark distributions and dihadron fragmentation functions,we estimate the sin ?R asymmetry of dihadron production in SIDIS at the kinematics of COMPASS and compare it with the COMPASS preliminary data.In addition,the prediction on the sin?R asymmetry at the typical kinematics of the future Electron Ion Collider is also presented.In order to test the reliability of the spectator model estimate,we compare the model result for the distribution hL with the Wandzura-Wilczek approximation for that distribution,and compare H1(?)with the existing parametrization.Second,we present a study on the double longitudinal-spin asymmetry of dihadron pro-duction in semi-inclusive deep inelastic scattering,in which the total transverse momentum of the final-state hadron pairs is integrated out.In particular,we investigate the origin of the cos ?R azimuthal asymmetry for which we take into account the coupling of the helicity distribution g1 and the twist-3 dihadron fragmentation function (?).We calculate the s-wave and p-wave interference term (?) in a spectator model.We estimate the cos ?R asymmetry at the kinemat-ics of COMPASS which is collecting data on dihadron production in polarized deep inelastic scattering.The prediction of the same asymmetry at JLab 12GeV and a future EIC are also presented.Our study indicates that measuring the cos ?R asymmetry in SIDIS may be a ideal way to probe the dihadron fragmentation function (?).