Constraints on the r Phase from B->K pi and B-> pi pi Decays and Possible Contribution frm New Physics

• Main Authors: Hsueh, Chien-Lan, 薛乾嵐
• Other Authors: Xiao-Gang He
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/59065802003739883674

碩士 === 國立臺灣大學 === 物理學研究所 === 88 === The measurement of parameters in the CKM matrix is of fundamental importance for both the precision description of the weak interaction of quarks and investigation of the mechanism of CP violation. In this thesis, I study several methods to determine the CP violating phase gamma in the Standard Model. The first method uses the constraints from update experimental data by a chi^2 analysis from which I obtain gamma to be 60 degrees. The second approach is to extract gamma by carrying out a numerical calculation of hadronic matrix elements for B -> K pi ,pi pi in model calculations. The preferred range of gamma is 62 - 73 degrees with experimental central values for B -> K pi if factorization calculations are valid. And the third method to constrain gamma using SU(3) symmetry for B^+ -> K^0 pi^+, K^+ pi^0 and B^+ -> pi^ + pi^0 decays. The present central values for the branching ratios constrain cos gamma to be less than 0.18 which implies gamma >= 79.8 degree and is in conflict with values obtained from the previous two methods. However, due to large theoretical and experimental errors, it is not possible to draw definite conclusion. One has to wait future experiments to provide more information. Finally, I show that new physics may have a significant effect on the determination of gamma. Using the anomalous gauge couplings as an example, it is found that the situation can be very different from the Standard Model within the allowed range.