Higgs-MediatedB0→μ+μ−in Minimal Supersymmetry

We demonstrate a new source for flavor-changing neutral currents within the minimal supersymmetric standard model. At moderate to large $\tan \beta$, it is no longer possible to diagonalize the masses of the quarks in the same basis as their Yukawa couplings. This generates flavor-violating couplings of the form ${\overline{b}}_R{d}_L\phi$ and ${\overline{b}}_R{s}_L\phi$ where $\phi$ is any of the three neutral, physical Higgs bosons. These new couplings lead to rare processes in the $B$ system such as $B^0\to {\mu }^{+}{\mu }^{-}$ and $B^0-{\overline{B}}^0$ mixing. We show that the latter are anomalously suppressed, while the former is in the experimentally interesting range, with an observable signal possible at Run II of the Tevatron if $m_A\lesssim 400–700\mathrm{GeV}$.