Search for top-jet resonances in the lepton+jets channel of ttbar + jets events with the ATLAS detector in 4.7 fb−1 of pp collisions at sqrt(s) = 7 TeV

This letter presents a search for a heavy new particle X produced singly in association with a t(tbar) quark. The new particle decays to a t(tbar) quark and a light flavor quark, leading to a color singlet (triplet) resonance in the t(tbar) + j system of the ttbar + jets signature. The full 2011 ATLAS pp collisions dataset from the LHC (4.7 fb-1) is used to select ttbar events produced in association with jets, in which one of the W bosons from the top quark decays leptonically and the other decays hadronically. The data are consistent with the standard model expectation and a new particle with mass below 350 (430) GeV for W (color triplet) models is excluded with a 95% confidence level, assuming unit right-handed coupling.