CMS Collaboration2017-10-052017-10-052016-12-22The CMS collaboration, Khachatryan, V., Sirunyan, A.M. et al. J. High Energ. Phys. (2016) 2016: 123. https://doi.org/10.1007/JHEP12(2016)123https://hdl.handle.net/1808/25084A first measurement of the top quark mass in the decay channel t → (W → ℓν) (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 8 TeV. 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.This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.http://creativecommons.org/licenses/by/4.0/Hadron-Hadron scattering (experiments)Top physicsArticle10.1007/JHEP12(2016)123openAccess