Measurement of the top pair invariant mass distribution and search for New Physics

Searches are presented for a massive particle decaying to a $\mathrm{t\bar{t}}$ pair, using the full CMS 2011 dataset of proton-proton collisions at a center of mass energy of 7 TeV, corresponding to an integrated luminosity of up to 5 fb$^{-1}$. The searches focus on resonant particles decaying to a top quark pair, generally referred to as a Z$^\prime$. Top quark decays to electrons, muons and hadrons are considered, leading to searches in final states using fully hadronic final states and final states with one and two leptons. The searches for Z$^\prime$ resonances look for resonant particles that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that may be partially or fully merged. 95\% confidence level upper limits up to 2.0 TeV/$c^2$ are set on the product of the production cross section and branching fraction for topcolor Z$^\prime$ modelled for several widths, as well as for Randall--Sundrum Kaluza--Klein gluons, which are excluded to values up to 1.5 TeV/$c^2$.