Sirunyan A.M. et al.PAO-TI CHANGKAI-FENG CHENWEI-SHU HOURONG-SHYANG LUStathes Paganis2021-07-282021-07-282019319007https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064123792&doi=10.1103%2fPhysRevLett.122.132001&partnerID=40&md5=78342f4e42b75c9492b53ee8967d990chttps://scholars.lib.ntu.edu.tw/handle/123456789/574655Signals consistent with the Bc+(2S) and Bc?+(2S) states are observed in proton-proton collisions at s=13 TeV, in an event sample corresponding to an integrated luminosity of 143 fb-1, collected by the CMS experiment during the 2015-2018 LHC running periods. These excited bc states are observed in the Bc+π+π- invariant mass spectrum, with the ground state Bc+ reconstructed through its decay to J/ψπ+. The two states are reconstructed as two well-resolved peaks, separated in mass by 29.1±1.5(stat)±0.7(syst) MeV. The observation of two peaks, rather than one, is established with a significance exceeding five standard deviations. The mass of the Bc+(2S) meson is measured to be 6871.0±1.2(stat)±0.8(syst)±0.8(Bc+) MeV, where the last term corresponds to the uncertainty in the world-average Bc+ mass. ? 2019 CERN for the CMS Collaboration. Published by the American Physical Society under the terms of the ?https://creativecommons.org/licenses/by/4.0/? Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Ground state; Mass spectrometry; Integrated luminosity; Invariant-mass spectra; Proton proton collisions; Standard deviation; Two-state; Excited statesjournal article10.1103/PhysRevLett.122.132001310126262-s2.0-85064123792