Implications of $b\rightarrow s\gamma $ decay measurements in testing   the MSSM Higgs sector
  The observation that the $b \rightarrow s\gamma $ decay rate is close to the Standard Model value implies a large mass for the charged-Higgs boson in the Minimum Supersymmetric Standard Model, that nearly closes the $t \rightarrow b H^+$ decay channel. For $m_t = 150$ GeV, the parameter region $m_A \ltap 130$ GeV is excluded; this largely pre-empts LEP II searches and also partially excludes a region that would be inaccessible to MSSM Higgs boson searches both at LEP II and at SSC/LHC. 
V. Barger, M. S. Berger and R. J. N. Phillips