Measurement of the mass of the top quark in decays with a J/ψ meson in pp collisions at 8 TeV

A first measurement of the top quark mass in the decay channel t → (W → lv)(b → J/ψ + X → µ⁺µ^- + X) is presented. The analysis uses events selected from the proton-proton collisions recorded by the CMS detector at the LHC at a center-of-mass energy of 8TeV. The data correspond to an integrated luminosity of 19.7 fb^-1, with 666 tt‾ and single top quark candidate events containing a reconstructed J/ψ candidate decaying into an oppositely-charged muon pair. The mass of the (J/ψ +l) system, where l is an electron or a muon from W boson decay, is used to extract a top quark mass of 173.5 ± 3.0 (stat) ± 0.9 (syst) GeV.