Searches for light charged Higgs bosons decaying to a hadronic tau and a neutrino in the one lepton mode with ATLAS

Light charged Higgs bosons could be produced in ttbar decay and the final state consists of a lepton, a tau-jet, 2 b-jets and several neutrinos. The latter makes the reconstruction of the complete event impossible. However, in the Minimal Supersymmetic extension of the Standard Model (MSSM) the branching ratio of the decay H+ -> tau nu is close to one for a wide parameter space and the signal appears as an excess of tau leptons in the final state over the main background (Standard Model ttbar events). Here, an ATLAS simulation study for this channel is introduced, problematic aspects are outlined, and the expected H+ sensitivity within the \mhmax~scenario of the MSSM is shown.