Rare three-body decay t -> ch gamma the standard model and the two-Higgs doublet model

摘要

A complete calculation of the rare three-body decay t -> ch gamma is presented in the framework of the standard model. In the unitary gauge, such a calculation involves about 20 Feynman diagrams. We also calculate this decay in the general two-Higgs doublet model (model III), in which it arises at the tree level. While in the standard model the decay t -> ch gamma is extremely suppressed, with a branching fraction of the order of 10(-15) for a Higgs boson mass of the order of 115 GeV, in the model III it may have a branching ratio up to 10(-5). We also discuss the crossed decay h -> b (s) over bar gamma.