$b \rightarrow s γ$ and $ε_b$ Constraints on Two Higgs Doublet Model

Abstract

We perform a combined analysis of two stringent constraints on the 2 Higgs doublet model, one coming from the recently announced CLEO II bound on $B(b \rightarrow s γ)$ and the other from the recent LEP data on $ε_b$. We have included one-loop vertex corrections to $Z \rightarrow b \overline b$ through $ε_b$ in the model. We find that the new $ε_b$ constraint excludes most of the less appealing window $\tanβ\lsim 1$ at $90\%$C.~L. for $m_t=150\GeV$. We also find that although $b \rightarrow s γ$ constraint is stronger for $\tanβ>1$, $ε_b$ constraint is stronger for $\tanβ\lsim 1$, and therefore these two are the strongest and complimentary constraints present in the charged Higgs sector of the model.