Signals consistent with the B_c^+(2S) and B_c^*+(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 b[over ¯]c states are observed in the B_c^+π^+π^- invariant mass spectrum, with the ground state B_c^+ 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 B_c^+(2S) meson is measured to be 6871.0±1.2(stat)±0.8(syst)±0.8(B_c^+) MeV, where the last term corresponds to the uncertainty in the world-average B_c^+ mass.
Observation of Two Excited B_c^+ States and Measurement of the B_c^+(2S) Mass in pp Collisions at sqrt[s]=13 TeV
Giannini, L;Ligabue, F;Manca, E;Mandorli, G;Rolandi, G;
2019
Abstract
Signals consistent with the B_c^+(2S) and B_c^*+(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 b[over ¯]c states are observed in the B_c^+π^+π^- invariant mass spectrum, with the ground state B_c^+ 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 B_c^+(2S) meson is measured to be 6871.0±1.2(stat)±0.8(syst)±0.8(B_c^+) MeV, where the last term corresponds to the uncertainty in the world-average B_c^+ mass.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
