Search for same-sign top quark pairs in the dimuon final state in the ATLAS experiment with 2/fb of data at √s = 7 TeV

The production of a pair of top quarks with same electric charges has been discussed as a signature for exotic colored states and also as a possible explanation for the observed deviation of top quark forward-backward asymmetry from the Standard model expectations at Tevatron. Therefore, a search for the same-sign top quark pair production is performed. As events with same-sign dimuon final states are very rare in the Standard model, the search is performed in this decay channel. The analysis uses the data from proton-proton collisions at 7 TeV center-of-mass energy at LHC, collected by ATLAS detector, with a total integrated luminosity of 2.05/fb. The analysis is based on cut and counting method. The background contribution is determined by using Monte Carlo simulations as well as data-driven methods. The observed number of events in data is consistent with the expected Standard model background within the uncertainties, therefore there is no evidence for new physics. The analysis result is used to set limits for various tt production models.