Search for charged Higgs bosons decaying via $H^+ \to \tau\nu$ in top quark pair events using $pp$ collision data at $\sqrt{s}=7$ TeV with the ATLAS detector

The results of a search for charged Higgs bosons are presented. The analysis is based on 4.6 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=7$TeV collected by the ATLAS experiment at the Large Hadron Collider, using top quark pair events with a $\tau$ lepton in the final state. The data are consistent with the expected background from Standard Model processes. Assuming that the branching ratio of the charged Higgs boson to a $\tau$ lepton and a neutrino is 100%, this leads to upper limits on the branching ratio of top quark decays to a $b$ quark and a charged Higgs boson between 5% and 1% for charged Higgs boson masses ranging from 90GeV to 160GeV, respectively. In the context of the $m_h^{\text{max}}$ scenario of the MSSM, $\tan\beta$ above 12–26, as well as between 1 and 2–6, can be excluded for charged Higgs boson masses between 90GeV and 150~GeV.