Study on internal hadron structure in RHIC-SPIN project

点击翻译按钮获取中文摘要

I investigated the spin observables measured at RHIC-SPIN program based on Quantum Chromodynamics, in particular, the single spin asymmetry for the pion production from the collision of unpolarized proton and transversely polarized proton and the A hyperon polarization from unpolarized pp collisions. Both of these quantities are known as twist-3 observables which represent quark-gluon correlation in the hadrons not incorporated in the parton model picture. According to a QCD analysis, the single spin asymmetry receives three kinds of twist-3 cross sections depending on where the twist-3 functions comes from : (i) twist-3 polarized distribution (ii) twist-3 unpolarized distribution, and (iii) twist-3 fragmentation function. Likewise the hyperon polarization receives two kinds of twist-3 cross sections : (a) twist-3 unpolarized distribution from the initial proton and (b) twist-3 polarized fragmentation function for the final A. I have derived the cross section formula from these contrib … More utions systematically, and estimated the magnitude employing a moderate model assumptions for the unknown twist-3 functions. I also applied the same method to semi-inclusive production of pion and A from the deep inelastic lepton-nucleon scattering.Next 1 studied the twist-2 double spin asymmetries for the hadron production with large transverse momentum in semi-inclusive deep Inelastic scattering. I have derived the cross section formula for all the possible spin configurations in the semi-inclusive deep inelastic scattering e+p → e÷h+X where the final hadron h can be pion or A and two of e, p, h are polarized. I also estimated these spin asymmetries using the parton densities in the literature at COMPASS and EIC energies and discussed their characteristic features.The sum rules on the first moment of the twist-3 parton distributions h_L(x), e(x) and g_T(x) are reexamined. One-loop correction to these distributions was calculated for a massive quark target. We found a δ(x) contribution for h_L(x) and e(x) and thus the sum rule is not satisfied for these functions, while there is no such δ(x) contribution for g_T(x). We presented an argument that this results can be generalized -nonperturbatively. Less