Search for a heavy top-quark partner in final states with two leptons with the ATLAS detector at the LHC

TL;DR

This paper reports a search for heavy top-quark partners decaying into a top quark and a neutral particle using ATLAS data, setting exclusion limits on their masses with no significant excess found.

Contribution

First search for heavy top-quark partners in dilepton final states at 7 TeV with ATLAS, establishing new mass exclusion limits.

Findings

Excluded top-quark partner masses between 300 and 480 GeV at 95% CL.

No significant excess over Standard Model background observed.

Set constraints on supersymmetric scalar top and spin-1/2 top-quark partner models.

Abstract

The results of a search for direct pair production of heavy top-quark partners in 4.7 fb-1 of integrated luminosity from pp collisions at sqrt(s) = 7 TeV collected by the ATLAS detector at the LHC are reported. Heavy top-quark partners decaying into a top quark and a neutral non-interacting particle are searched for in events with two leptons in the final state. No excess above the Standard Model expectation is observed. Limits are placed on the mass of a supersymmetric scalar top and of a spin-1/2 top-quark partner. A spin-1/2 top-quark partner with a mass between 300 GeV and 480 GeV, decaying to a top quark and a neutral non-interacting particle lighter than 100 GeV, is excluded at 95% confidence level.