Search for Charged Higgs bosons produced in top quark decays with the ATLAS detector at the LHC

The sensitivity of the ATLAS detector to a signal of MSSM charged Higgs bosons in the low mass region (m_H+/-<m_t) is presented. In this case, the charged Higgs can be produced in top decays competing with the usual weak decay of the top quark. In this report, the emphasis is put on a new approach: the hadronic final states pp-->WbHb-->(qq)b(tau nu)b are used. This channel provides a complete coverage of the tanb range if BR(t --> H+/- b) is greater than a few percents, enhancing the ATLAS sensitivity to H+/- in a non covered region. The possibility to measure the charged Higgs mass and the achievable precision are also discussed.