大加速器时代B介子衰变的精确计算

B介子稀有衰变是检验标准模型，探测CP破坏起源和寻找新物理的理想场所。B介子工厂和LHCb实验已经测量了上百个衰变过程，即将投入使用的超级B工厂Belle II实验将会收集到比B工厂多两个量级的实验数据。海量实验数据要求精确的理论计算，理论上的处理方法通常采取因子化方案进行标度分离，将强子矩阵元简化成低能非微扰物理量和可以微扰计算的硬散射核部分。本研究项目将研究一些有意义的两体和三体B介子非轻弱衰变，拟通过计算高阶圈图提高短程计算精度，设计一个可以处理一般性过程的计算程序；结合低能手征有效理论和格点量子色动力学更加精确的抽取非微扰参量；进一步地发展微扰量子色动力学因子化方法。同时，我们还将利用有效理论的方法，研究双重味Bc介子的湮灭型衰变过程，这些研究将为抽取Bc强子矩阵元提供必要的理论基础。

Rare decays of B mesons are among the ideal platforms to test the standard model of particle physics, explore the source for CP violation and search for new physics beyond the standard model. The two B factories and the LHCb collaboration have accumulated abundant data on B meson decays, and in this future the Belle II experiment can collect more data by two orders of magnitude. Accordingly it is mandatory to improve the theoretical prediction. Theoretical study relies heavily on the factorization approach, which can separate the short-distance (high scale) and long-distance (low scale) physics. This research proposal will study some interesting two-body and three-body rare decays of B meson, and plans to: calculate higher order perturbative contributions; make use of chiral perturbation theory and Lattice QCD and provide methods that can extract low energy inputs; further develop the perturbative QCD factorization approach. Making use of the effective field theory, we will also study the annihilation type decay of the Bc meson. Since these modes are the simplest Bc decay modes, they can provide methods for the extraction of Bc matrix elements in the effective field theory.