【作者】 徐栋；

【导师】 何小刚；

【作者基本信息】 上海交通大学 ， 物理学， 2014， 硕士

【摘要】 粒子物理的标准模型是描述夸克轻子等基本粒子的基础理论,实验数据也证明了标准模型的巨大成功。本文在粒子物理标准模型的框架下研究了夸克味道混合矩阵的参数化的问题,以及从夸克味道对称性角度研究了带电三体非轻衰变的问题。在夸克味道混合矩阵的参数化研究中,在介绍了之前研究中选取三个夸克混合角和一个CP破坏相角作为参数的九种参数化方法之后,指出了在这九种方法中,参数值具有参数化依赖的问题。在本文新建立的参数化方法中,选取三个CKM矩阵元模值和幺正三角形三个内角,,和之一作为参数的方法,解决了参数值的参数化依赖问题。并证明了新建立的种参数化方法的等价性。最后给出了对应新的参数化方法的类似Wolfenstein参数化的近似展开的方法。在B^+-介子带电三体衰变研究中,从味对称性出发系统地构建了介子衰变到π⁺π⁺π^-,π⁺K⁺K^-,K⁺π⁺π^-,K⁺K⁺K^-末态的四个衰变的振幅,同时考虑了由于夸克质量之差导致的对称性的破坏以及对末态粒子场求导数导致的动量依赖的振幅贡献。通过数值计算分析发现,只有考虑了较大的对称性破坏效应才可以很好的解释实验数据。最后把从味对称性的分析方法用到+,0,0的衰变中。在考虑全对称的衰变振幅的情况下,找出了不同的衰变道之间衰变振幅的一些线性的关系,并且在分别考虑了和同位旋对称破坏时,找出了不受对称性破坏影响的衰变振幅之间的线性关系。更多还原

【Abstract】 The Standard Model is a fundamental theory describing the elementary particles such as quarks and leptons, whose great success is confirmed by the experimental data. We studied the new ways to parameterize the CKM matrix, which describes the quark flavor mixing. And we also studied the charged three-body decays of B± meson in terms of quark SU(3) flavor symmetry.In the study of new parametrization of CKM matrix, after introducing nine kinds of equivalent parametrization with three quark flavor mixing angles and one CP phase as the independent parameters, we pointed out that the values of parameters would depend on the parametrization ways. We constructed new methods to parameterize the CKM matrix using three absolute values of CKM matrix elements and one of a, β, or γ angles defined by the unitary property of CKM matrix, which resolved the problem that the values of parametrization will depend on the chosen parametriza-tion. Consequently, we demonstrated that these 12 kinds of new ways of parametriza-tion are equivalent between each other. Then, we showed the way how to develop the Wolfenstein-like expression of these 12 new parametrizaitons.In the study of charged three-body B+ meson decays, under the SU(3) flavor symmetry, we constructed the decay amplitudes systematically for the decay modes:B+ → π+π+π-, π+K+K-,K+π+π-,K+K+K-. Meanwhile, we also considered the momentum dependent part of the decay amplitudes resulted from derivatives of independent terms and the flavor symmetry breaking effects resulted from mass differ-ence between different quarks. After carrying out the numerical analysis, we found that it was necessary to take the large flavor symmetry breaking effects into consideration in order to explain the corresponding experimental data well. At last, we extend the analysis from SU(3) flavor symmetry to the decays of B+, Bd0, Bs0 mesons, and found the linear relations between different decay modes in terms of their fully-symmetric decay amplitudes. We also identified the linear relations that still hold when the flavor SU(3) and isospin symmetry breaking effects were taken into account.更多还原