Sirunyan, A. M.Tumasyan, A.Adam, W.Ambrogi, F.Bergauer, T.Brandstetter, J.Dragicevic, M.2025-03-232025-03-2320200031-90071079-7114https://doi.org/10.1103/PhysRevLett.124.202001https://hdl.handle.net/11486/5501A measurement is reported of the jet mass distribution in hadronic decays of boosted top quarks produced in pp collisions at root s = 13 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 35.9 fb(-1). The measurement is performed in the lepton + jets channel of t (t) over bar events, where the lepton is an electron or muon. The products of the hadronic top quark decay t -> bW -> bq (q) over bar' are reconstructed as a single jet with transverse momentum larger than 400 GeV. The t (t) over bar cross section as a function of the jet mass is unfolded at the particle level and used to extract a value of the top quark mass of 172.6 +/- 2.5 GeV. A novel jet reconstruction technique is used for the first time at the LHC, which improves the precision by a factor of 3 relative to an earlier measurement. This highlights the potential of measurements using boosted top quarks, where the new technique will enable future precision measurements.eninfo:eu-repo/semantics/openAccessArticle1242010.1103/PhysRevLett.124.202001325010482-s2.0-85086052956Q1WOS:000534428700003Q1