B-meson dileptonic decays enhanced by supersymmetry with large $\tan\beta$

We examined the rare decays $B\to X_s\ell^+\ell^-$ and $B_s\to\ell^+\ell^-\gamma$ in the minimal supersymmetric model with large $\tan\beta$. Taking into account the gluino-loop and neutralino-loop effects, we found that for a large $\tan\beta$ the neutral Higgs exchanging diagrams could enhance $Br(B\to X_s\tau^+\tau^-)$ by a factor of 5 and $Br(B_s\to\tau^+\tau^-\gamma)$ by a couple of orders in some part of supersymmetric parameter space allowed by current experiments such as $b\to s\gamma, B\to K^{(*)}\ell^+\ell^-$ and $B_s\to\ell^+\ell^-$. The forward-backward asymmetry and the distributions of differential branching ratios are also found to differ significantly from the standard model results. Such enhanced branching ratios reach the level of $10^{-5}$ and thus might be observable in the new generation of B experiments.