A search for $tart$ resonances with the ATLAS detector in 2.05 fb$^-1$ of proton-proton collisions at $sqrts=7$ TeV

Abstract

A search for top quark pair resonances in final states containing at least one electron or muon has been performed with the ATLAS experiment at the CERN Large Hadron Collider. The search uses a data sample corresponding to an integrated luminosity of 2.05 fb^-1, which was recorded in 2011 at a proton-proton centre-of-mass energy of 7 TeV. No evidence for a resonance is found and limits are set on the production cross-section times branching ratio to ttbar for narrow and wide resonances. For narrow Z_s14 bosons, the observed 95% credibility level limits range from 9.3 pb to 0.95 pb for masses in the range of m_Z_s14 = 500 GeV to m_Z_s14 = 1300 GeV. The corresponding excluded mass region for a leptophobic topcolour Z_s14 boson (Kaluza-Klein gluon excitation in the Randall-Sundrum model) is m_Z_s14 < 880 GeV (m_{g_KK} < 1130 GeV).