Measurement of the top pair invariant mass distribution at 7 TeV and search for New Physics

We present a measurement of the top-pair mass in tt events by using proton-proton collisions at the LHC at a centre-of-mass energy of 7 TeV. We use data collected with the CMS experiment during the year 2010, and amounting to a total integrated luminosity of 36 pb-1. The analysis is performed by a full top-pair event reconstruction and by combining the electron+jets and muon+jets channels. The measurement is then used for searching for production of a massive, narrow-width, neutral boson decaying into top-pairs. We observe no significant deviations from the QCD expectations, therefore we translate the measurement into an upper limit on the new physics production cross-section as a function of the particle mass.