ATLAS discovery prospects for a light charged Higgs, H+ to csbar

We present the ATLAS sensitivity for light charged Higgs boson searches at 7 TeV. In some models beyond the Standard Model, including the Minimal Super-symmetric Model (MSSM), charged Higgs bosons can be produced in top quark decays. We study the ATLAS sensitivity to a light charged Higgs in the H+ to csbar decay channel. With 1fb^-1 of expected data, we find that ATLAS sensitivity to the light charged Higgs improves substantially on the current Tevatron upper limits on B(t to bH+).