Observation of Two Excited B_{c}^{+} States and Measurement of the B_{c}^{+}(2S) Mass in pp Collisions at sqrt[s]=13 TeV.

Observation of Two Excited B_{c}^{+} States and Measurement of the B_{c}^{+}(2S) Mass in pp Collisions at sqrt[s]=13 TeV.

Physical review letters (2019-04-24)

A M Sirunyan, A Tumasyan, W Adam, F Ambrogi, T Bergauer, J Brandstetter, M Dragicevic, J Erö, A Escalante Del Valle, M Flechl, R Frühwirth, M Jeitler, N Krammer, I Krätschmer, D Liko, T Madlener, I Mikulec, N Rad, J Schieck, R Schöfbeck, M Spanring, D Spitzbart, W Waltenberger, J Wittmann, C-E Wulz, M Zarucki, V Drugakov, V Mossolov, J Suarez Gonzalez, M R Darwish, E A De Wolf, D Di Croce, X Janssen, J Lauwers, A Lelek, M Pieters, H Van Haevermaet, P Van Mechelen, N Van Remortel, F Blekman, E S Bols, S S Chhibra, J D'Hondt, J De Clercq, G Flouris, D Lontkovskyi, S Lowette, I Marchesini, S Moortgat, L Moreels, Q Python, K Skovpen, S Tavernier, W Van Doninck, P Van Mulders, I Van Parijs, D Beghin, B Bilin, H Brun, B Clerbaux, G De Lentdecker, H Delannoy, B Dorney, L Favart, A Grebenyuk, A K Kalsi, J Luetic, A Popov, N Postiau, E Starling, L Thomas, C Vander Velde, P Vanlaer, D Vannerom, Q Wang, T Cornelis, D Dobur, A Fagot, M Gul, I Khvastunov, C Roskas, D Trocino, M Tytgat, W Verbeke, B Vermassen, M Vit, N Zaganidis, O Bondu, G Bruno, C Caputo, P David, C Delaere, M Delcourt, A Giammanco, G Krintiras, V Lemaitre, A Magitteri, K Piotrzkowski, J Prisciandaro, A Saggio

PMID31012626

摘要

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.