General scan in flavor parameter space in models with vector quark doublets and an enhancement in the B→X_sγ process  

作　　者：王雯宇 熊兆华 赵新彦 

机构地区：[1]Institute of Theoretical Physics, Beijing University of Technology

出　　处：《Chinese Physics C》2016年第9期20-28,共9页中国物理C（英文版）

基　　金：Supported by Natural Science Foundation of China(11375001);Talents Foundation of Education Department of Beijing

摘　　要：In models with vector-like quark doublets, the mass matrices of up and down type quarks are related.Precise diagonalization of the mass matrices has become an obstacle in numerical studies. In this work we first propose a diagonalization method. As its application, in the Standard Model with one vector-like quark doublet we present the quark mass spectrum and Feynman rules for the calculation of B → Xsγ. We find that i） under the constraints of the CKM matrix measurements, the mass parameters in the bilinear term are constrained to a small value by the small deviation from unitarity; ii） compared with the fourth generation extension of the Standard Model, there is an enhancement to the B → Xsγ process in the contribution of vector-like quarks, resulting in a non-decoupling effect in such models.In models with vector-like quark doublets, the mass matrices of up and down type quarks are related.Precise diagonalization of the mass matrices has become an obstacle in numerical studies. In this work we first propose a diagonalization method. As its application, in the Standard Model with one vector-like quark doublet we present the quark mass spectrum and Feynman rules for the calculation of B → Xsγ. We find that i） under the constraints of the CKM matrix measurements, the mass parameters in the bilinear term are constrained to a small value by the small deviation from unitarity; ii） compared with the fourth generation extension of the Standard Model, there is an enhancement to the B → Xsγ process in the contribution of vector-like quarks, resulting in a non-decoupling effect in such models.

关 键 词：FCNC vector like particle CKM matrix 

分 类 号：O572.33[理学—粒子物理与原子核物理]