Charged MSSM Higgs Boson Observability in the $H^{+-} \to tb$ Decay

The discovery potential for a heavy charged MSSM Higgs boson is studied in the H+/- -> tb decay channel. Two strategies based on the tagging of either three or four b jets are considered. In both cases the main background from ttbar + jets, with either additional b jets or jets mistagged as b, is found to be very large and kinematically similar to the signal. Systematic uncertainties on the background cross section and their impact on the search are also assessed. The discovery potential is investigated and no sensitivity for this channel is obtained in the MSSM parameter space. Assuming the same signal kinematics as in the MSSM, the cross section needed for a five--sigma discovery of a charged Higgs--boson signal is presented.