双光子交换效应: 强子模型、色散关系和低能有效理论

高精度测量和精确检验在粒子物理甚至原子物理中逐渐发挥越来越重要的作用。对于强相互作用相关物理量的高精度测量可以精确检验强相互作用相关的各种唯象模型、反应机制和计算方法，增进我们对QCD相关性质的理解。. 高精度测量必须结合相应精度的理论计算才能反推出物理量，双光子交换效应的精确计算正是高精度抽取核子和pi介子形状因子的关键之一，目前最可靠的计算方法有强子模型方法和色散关系方法。本项目计划以几个具有普适形式的低能有效相互作用为例，通过解析计算和数值验证，指出这两个计算方法之间的内在关系，由此改进并统一这两个方法的计算结果，并讨论改进后的计算结果在低能极限下与低能有效理论之间的关联，最终给出轻子和核子/pi介子弹性散射中双光子交换效应的一般性结果，为高精度实验数据的分析提供理论计算基础。

The high precise measurements and experiments play more and more important roles in the particle physics and the atomic physics. The precise extraction of the physical quantities in QCD can test the QCD related phenomenological models, theoretical methods and imporve our understanding on QCD. . The corresponding precise and reliable theoretical calculations are necessary to extract the physical quantities from the precise experimental data sets. The two-photon-exchange (TPE) effects must be considered carefully to extract the form factors of nucleon. To estimate the TPE effects, the hadronic model (HM) method and the dispersion relation (DR) method are usually used and at present they are the most reliable two methods. In this project, we plan to take some low energy interactions as examples to show the internal relations between the HM method and the DR method, then improve and unify these two methods. The results by the modified method in the low energy limit can be compared with those by the low energy effective theory. After these improvements and comparisons, we can get the strict expressions for the TPE effects. These results can be applied to analysis the precise experimental data sets and help us understand these precise data sets in a consistent way.