Observation of new excited B0s states

A structure is observed in the B± K ∓ mass spectrum in a sample of proton–proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb−1 . The structure is interpreted as the result of over-lapping excited B0s states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to B± K ∓, are
determined to be
m1 = 6063.5 ± 1.2 (stat) ± 0.8 (syst) MeV,
1 = 26 ± 4 (stat) ± 4 (syst) MeV,
m2 = 6114 ± 3 (stat) ± 5 (syst) MeV,
2 = 66 ± 18 (stat) ± 21 (syst) MeV.
Alternative values assuming a decay through B∗± K ∓, with a missing photon from the B∗± → B±γ decay, which are shifted by approximately 45 MeV, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed B∗0s2 state is determined to be 0.87 ± 0.15 (stat) ± 0.19 (syst).