$b\to s\gamma$ and $Z\to b\overline{b}$ Constraints on Two Higgs Doublet Model

Abstract

We perform a combined analysis of two stringent constraints on two Higgs doublet model, coming from the recently announced CLEO II bound on $B(b\to s\gamma )$ and $Z\to b\overline{b}$ and from the recent LEP data on the ratio $\frac{\Gamma (Z\to b\overline{b})}{\Gamma (Z\to hadrons)}$. We include one-loop vertex corrections to $Z\to b\overline{b}$ in the model. We find that although the CLEO II bound serves as the strongest constraint present in the charged Higgs sector of the model, the current LEP value for $R_b$ may also provide a further constraint for $\tan \beta <1$.

Comments: LATEX, 6 Pages, 2 Figures available upon request, CTP-TAMU-54/93, ACT-21/93