Top Mass Measurement at CMS

Given the big cross section for \ttbar production in proton-proton collisions at 14\TeV, the LHC with its high luminosity will be, among others,a top factory, allowing a precision measurement of the top quark mass. Based on a detailed simulation of the CMS detector, the following top mass reconstruction accuracies are possible in the respective final states with the present knowledge of experimental and theoretical uncertainties. Delta m_t (di-leptonic, 1fbinv) = pm 1.5 (stat) pm 2.9 (syst.) GeVcc Delta m_t (semi-leptonic, 1fbinv) = pm 0.7 (stat) pm 1.9 (syst.) GeVcc Delta m_t (fully hadronic, 1fbinv) = pm 0.6(stat) pm 4.2 (syst.) GeVcc Delta m_t (di-leptonic}, 10 fbinv) = pm 0.5 (stat) pm 1.1 (syst.) GeVcc Delta m_t (semi-leptonic, 10 fbinv) = pm 0.2 (stat) pm 1.1 (syst.) GeVcc Delta m_t (JPsi, 20 fbinv) = pm 1.2 (stat) pm 1.5 (syst.) GeVcc A combined top mass accuracy of mathcal O (1GeVcc) for 10-20fbinv of well-understood CMS data will be feasible.