Systematics in charged Higgs searches in ATLAS

sor H + ! τν has been studied for the ATLAS experiment, for masses lighter than the top quark mass. The first channel, dominating in the low tan β region ( 3), is searched in two leptons, two jets and missing energy final state. In both c ases, the W boson from the other top quark is required to decay leptonically. The study has been performed using a realistic detector simulation for the signal and the SM backgrounds. The discovery sensitivity and the upper limit on B (t ! bH + ) as a function of mH+ , assuming 100% branching ratios of charged Higgs boson either to H + ! c ¯ s or H + ! τν, were discussed for different integrated luminosity and ce nter-of-mass energy scenarios: at p s = 10 TeV and R L dt = 200 pb 1 and at p s = 7 TeV with R L dt = 1 fb 1 . The results for the lower center-of-mass energy were obtained from those at higher by means of rescaling cross-sections for the relevant processes. The main focus o f the present paper is on the impact of systematics on these results.