Search for high-mass resonances decaying to top quark pairs in the lepton+jets channel

We perform a model-independent search for the production of heavy resonances with mass greater than 1~TeV decaying to top quark pairs. Using data samples corresponding to $\sim 5.0~\rm fb^{-1}$ of integrated luminosity of proton-proton collision data recorded with the CMS experiment in 2011 at $\sqrt{s} = 7$~TeV, we select events containing one lepton (electron or muon) and at least two jets and look for excesses above standard model background prediction in the top quark pair invariant mass spectrum. The high transverse momenta of the top quarks originating from such decays result in an event topology which requires a dedicated event selection and reconstruction of the invariant top quark pair mass. We use a $\chi^2$ method in the reconstruction and selection of top quark pairs and apply b-tagging to improve sensitivity. In the absence of evidence for a signal, we evaluate 95\% C.L. upper limits on $\sigma(\rm pp \rightarrow \rm Z' \rightarrow \rm t\bar t)\cdot \rm BR$ as a function of the invariant mass of the resonance.