Signals consistent with the Bc+(2S) and Bc∗+(2S) states are observed in proton-proton collisions at sqrt(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.
Observation of Two Excited Bc+ States and Measurement of the Bc+ (2S) Mass in pp Collisions at sqrt(s) =13 TeV
Meridiani P.;Amapane N.;Argiro S.;Bellan R.;Costa M.;Covarelli R.;Kiani B.;Migliore E.;Monaco V.;Monteil E.;Obertino M. M.;Pacher L.;Pinna Angioni G. L.;Romero A.;Sacchi R.;Sola V.;Solano A.;Rumerio P.;Ravera F.;
2019-01-01
Abstract
Signals consistent with the Bc+(2S) and Bc∗+(2S) states are observed in proton-proton collisions at sqrt(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.File | Dimensione | Formato | |
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PhysRevLett.122.132001.pdf
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