B →$_{tv}X$ decays in a two higgs doublet model

Abstract

We have first reviewed the HQET and spin-flavor symmetry, which are important systematic tools in studying the properties of the heavy hadrons. With the HQET and spin-flavor symmetry, we calculated the non-perturbative contributions of the inclusive semileptonic B $\rightarrow$ $\tau\nu$X decays within two Higgs doublet model. We obtained the $\tau$ spectrum and total decay rate. Further-more comparing our theoretical results with the experimental B $\rightarrow$ $e\nu$ branching ratio, we could find the B $\rightarrow$ $\tau\nu$ X branching ratio. It gives a refined constraint of the value tan $\beta$ in two Hidds doublet model.