Possibility of $m_t<M_W+m_b$ for SUSY-type of Two Higgs Doublet Model

Abstract

Allowing for realistic uncertainties in input parameters, we demonstrate that the present CLEO limit of $5.4\times 10^{-4}$ for inclusive $b\to s\gamma$ decay does not yet fully exclude the $t\to b{H}^{+}$ decay possibility in supersymmetric type of two Higgs doublet models. Combined with direct search for $t\to b{H}^{+}$ via $H^{+}\to {\tau }^{+}\nu$ at the Tevatron, we conclude that $\tan \beta \sim 1$ is the ``allowed" window for $m_{H^{+}}<m_t<M_W$. The possibility becomes excluded, however, {\it if} the CLEO limit is pushed below $4\times 10^{-4}$.

Comments: 11 pages + 3 Figures (not included), ReVTeX, NTUTH-94-15 and NHCU-HEP-94-16