Search for tb resonances in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector

TL;DR

This paper reports a search for W' resonances decaying to top and bottom quarks in proton-proton collisions at 7 TeV using the ATLAS detector, setting new mass limits and no evidence of such particles was found.

Contribution

First search for W'_R resonances in tb final states at 7 TeV with ATLAS, establishing mass exclusion limits up to 1.13 TeV.

Findings

No significant excess observed in data.

Excluded W'_R masses below 1.13 TeV at 95% CL.

Set upper limits on cross section times branching ratio.

Abstract

This Letter presents a search for tb resonances in 1.04/fb of LHC proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 7 TeV. Events with a lepton, missing transverse momentum, and two jets are selected and the invariant mass of the corresponding final state is reconstructed. The search exploits the shape of the tb invariant mass distribution compared to the expected Standard Model backgrounds. The model of a right-handed W'_R with Standard Model-like couplings is chosen as the benchmark model for this search. No statistically significant excess of events is observed in data, and upper limits on the cross section times the branching ratio of W'_R resonances at 95% CL lie in the range 6.1-1.0 pb for W'_R masses ranging from 0.5 to 2.0 TeV. These limits are translated into a lower bound on the allowed right-handed W'_R mass, giving m_{W'_R} > 1.13 TeV at 95% CL.