Search for charged Higgs bosons through the violation of lepton universality in ttbar events using pp collision data at √s = 7 TeV with the ATLAS experiment

ATLAS COLLABORATION, G. AAD, F. MONTICELLI, ET AL

JOURNAL OF HIGH ENERGY PHYSICS

SPRINGER

Lugar: Berlin; Año: 2012 vol. 2013 p. 1 - 45

1126-6708

In several extensions of the Standard Model, the top quark can decay into a bottom quark and a light charged Higgs boson H (+), t → bH (+), in addition to the Standard Model decay t → bW. Since W bosons decay to the three lepton generations equally, while H (+) maypredominantlydecayinto τν, charged Higgs bosons can be searched for using the violation of lepton universality in top quark decays. The analysis in this paper is based on 4.6 fb(−1) of proton-proton collision data at TeV collected by the ATLAS experiment at the Large Hadron Collider. Signatures containing leptons (e or μ) and/or a hadronically decaying τ (τ (had)) are used. Event yield ratios between e + τ (had) and e + μ, as well as between μ + τ (had) andμ + e, final states are measured in the data and compared to predictions from simulations. This ratio-based method reduces the impact of systematic uncertainties in the analysis. No significant deviation from the Standard Model predictions is observed. With the assumption that the branching fraction (H (+) → τν) is 100%, upper limits in the range 3.2%–4.4% can be placed on the branching fraction (t → bH (+)) for charged Higgs boson masses m ( )H(+) in the range 90–140 GeV. After combination with results from a search for charged Higgs bosons in decays using the τ (had) + jets final state, upper limits on (t → bH (+)) can be set in the range 0.8%–3.4%, for m ( )H(+) in the range 90-160 GeV.In several extensions of the Standard Model, the top quark can decay into a bottom quark and a light charged Higgs boson H+, t to bH+, in addition to the Standard Model decay t to bW. Since W bosons decay to the three lepton generations equally, while H+ may predominantly decay into tau+nu, charged Higgs bosons can be searched for using the violation of lepton universality in top quark decays. The analysis in this paper is based on 4.6/fb of proton-proton collision data at sqrt(s) = 7 TeV collected by the ATLAS experiment at the Large Hadron Collider. Signatures containing leptons (e or mu) and/or a hadronically decaying tau (tau_had) are used. Event yield ratios between e+tau_had and e+mu, as well as between mu+tau_had and mu+e, final states are measured in the data and compared to predictions from simulations. This ratio-based method reduces the impact of systematic uncertainties in the analysis. No significant deviation from the Standard Model predictions is observed. With the assumption that the branching fraction B(H+ to tau+nu) is 100%, upper limits in the range 3.2%-4.4% can be placed on the branching fraction B(t to bH+) for charged Higgs boson masses m(H+) in the range 90-140 GeV. After combination with results from a search for charged Higgs bosons in ttbar decays using the tau_had+jets final state, upper limits on B(t to bH+) can be set in the range 0.8%-3.4%, for m(H+) in the range 90-160 GeV.