Univ Munich, Sekt Phys, D-80333 Munich, Germany; Chinese Acad Sci, Inst Theoret Phys, Beijing 100080, Peoples R China
英文摘要:
A systematic investigation on the muon's anomalous magnetic moment and a related lepton flavor-violating process such as mu --> egamma, tau --> egamma and tau --> mugamma is made at the two-loop level in the models with flavor-changing scalar interactions. The two-loop diagrams with double scalar exchanges are studied and their contributions are found to be compatible with the ones from the Barr-Zee diagram. By comparing with the latest data, the allowed ranges for the relevant Yukawa couplings Y-ij in the lepton sector are obtained. The results show the hierarchical structure Y-mue,Y-taue much less than Y-mutau similar or equal to Y-mumu in the physical basis if Deltaalpha(mu) is found to be > 50 x 10(-11). It deviates from the widely used ansatz in which the off-diagonal elements are proportional to the square root of the products of the related fermion masses. An alternative Yukawa coupling matrix in the lepton sector is suggested to understand the current data. With such a reasonable Yukawa coupling ansatz, the decay rate of tau --> mugamma is found to be near the current experiment upper bound.
