Various weak processes at the hadronic scale have been utilized to search for new physics at high energy scale, which can be described by the QCD chiral Lagrangian matched from the low-energy effective theory (LEFT). Utilizing the chiral symmetry SU(2)L×SU(2)R→SU(2)V at the quark and hadronic levels, we make a comprehensive comparison of various matching methods, including the external source method, conventional spurion method, and our systematic spurion method. Although different methods show agreements for dimension-6 LEFT operator matching, we find that for higher-dimensional operators, the external source method is quite limited or inapplicable, the conventional spurion methods needs to introduce more and more spurions, while our spurion method does not need to introduce any new spurions than the ones in the dimension-6 matching. Using minimal set of spurions, we thus establish an one-to-one correspondence between the LEFT and chiral operators, with several examples, such as derivative operators at dimensions 7 and 8 with a single bilinear, four-quark operators at the dimension-9 level with two quark bilinears, which can be applied to the study of neutrino/electron scatterings and neutrinoless double beta decay.

Biography

李刚，中山大学物理与天文学院副教授。2017年博士毕业于北京大学，先后在台湾大学和马萨诸塞大学阿默斯特分校做博士后。主要研究方向为超出标准模型的新物理，目前集中在中微子相关的新物理唯象研究。

Inviter: Jiang-Hao Yu