A Search for a light charged Higgs boson decaying to cs ̄ in pp collisions at √s = 7 TeV with the ATLAS detector

We present the search results for a light charged Higgs boson produced in top quark decays and decaying into two jets in pp collisions at √s = 7 TeV with the ATLAS detec- tor. The analysis uses a data sample collected during 2010, corresponding to an integrated luminosity of 35 pb−1. The search is based on the semi-leptonic decay channel of tt ̄ candi- dates and analyzes the invariant mass distribution of two jets in the final state. The data are found to be in good agreement with the expectation from the Standard Model background processes and 95% upper limits are set on the decay branching ratio of top quarks to charged Higgs bosons that decay into cs ̄/c ̄s.