Transverse mass observables for charged Higgs searches in top decays at the LHC

Light charged Higgs bosons (mH+<mtop), if exist, are expected to be copiously produced at the LHC via top quark decays t→H+b. The dominant decay mode in this mass range is to a τ-lepton and a neutrino. We study the semi-leptonic and di-leptonic channels in which the τdecays leptonically (i.e. to an electron or a muon). The presence of an isolated lepton offers a cleaner experimental signature compared to hadronic τdecays, however reconstruction of the event is more challenging due to the presence of multiple neutrinos in the final state. We define a new transverse mass for the charged Higgs in these channels, which can be used to discriminate between the signal and the main background on a statistical basis.