本项目基于非相对论量子色动力学(NRQCD)，来研究P波粲夸克偶素chi_J衰变到双光子过程总宽度及螺旋度宽度的相对论修正和辐射修正。对于chi_J衰变到双光子的过程，由于目前文献中的理论结果存在分歧，所以对此过程的研究可以澄清已有理论矛盾。最新BESIII的实验测量与NRQCD的理论预言相差甚远，考虑相对论修正和辐射修正将有助于减轻甚至解决实验和理论的矛盾。另外BESIII还第一次测量了此过程的螺旋度宽度，因此本项目还将对螺旋度宽度的相对论修正和辐射修正进行研究，并结合实验进行深入的唯像分析。

Based on nonrelativistic QCD (NRQCD), we study the relativistic and radiative corrections to both the total decay rate and helicity decay rate for the process of chi_cJ decay into double photons. Since the theoretical predictions for this process are not constistent with each other in current references, our study will help to clarify this contradiction. In addition, the newest experimental measurements do not agree with NRQCD prediction, hence our relativistic and radiative corrections will help to relieve and even eliminate the contradiction. Moreover, BESIII measures the helicity decay rates for chi_cJ to double photons, in this projdect, we will also study the heliciy decay rate, and then present the phenomenological analysis.