A search for ttbar resonances with the ATLAS detector in 2.05 fb^-1 of proton-proton collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports a search for top quark pair resonances in proton-proton collisions at 7 TeV using ATLAS data, setting limits on potential new particles but finding no evidence of such resonances.

Contribution

It presents the first search for ttbar resonances at 7 TeV with ATLAS, establishing new limits on resonance production cross-sections and mass exclusions.

Findings

No evidence for ttbar resonances was observed.

Limits set on resonance cross-sections and mass ranges.

Excluded mass regions for specific Z' models.

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' bosons, the observed 95% credibility level limits range from 9.3 pb to 0.95 pb for masses in the range of m_Z' = 500 GeV to m_Z' = 1300 GeV. The corresponding excluded mass region for a leptophobic topcolour Z' boson (Kaluza-Klein gluon excitation in the Randall-Sundrum model) is m_Z' < 880 GeV (m_{g_KK} < 1130 GeV).