Search for charge-asymmetric production of W$′$ bosons in $t\bar{t} +$ jet events from pp collisions at $\sqrt{s} =$ 7 TeV

A search is presented for charge-asymmetric production of a W' boson that has been proposed to accommodate the forward-backward asymmetry observed in the production of top-antitop quark pairs at the Tevatron. The new heavy W' boson would be produced in association with a top quark and would decay into top and down quarks. The data correspond to an integrated luminosity of 5.0 inverse femtobarns in pp collisions at a center-of-mass energy of 7 TeV, recorded by the CMS detector at the LHC. No significant excess above the standard model expectations is observed, and, from a combination of the electron-plus-jets and muon-plus-jets channels, a 95% confidence level lower limit of 840 GeV is set on the W' boson mass for a W' boson model with values for coupling constants to top and down quarks g(L) = 0 and g(R) = 2. In addition, a kinematic reconstruction of the W' resonance mass using the inherent charge asymmetry of this model finds no indication of the presence of W' events in the data.