Observation of the decay [bar over B][0 over s] → ψ(2S)K[superscript +]π[superscript −]

Abstract

The decay [bar over B][0 over s] → ψ(2S)K[superscript +]π[superscript −] is observed using a data set corresponding to an integrated luminosity of 3.0 fb[superscript −1] collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. The branching fraction relative to the B[superscript 0] → ψ(2S)K[superscript +]π[superscript −] decay mode is measured to be [B([bar over B][0 over s] → ψ(2S)K[superscript +]π[superscript −]) over B[superscript 0] → ψ(2S)K[superscript +]π[superscript −] = 5.38 ± 0.36(stat) ± 0.22(syst) ± 0.31(f[subscript s]/f[subscript d])%, where f[subscript s]/f[subscript d] indicates the uncertainty due to the ratio of probabilities for a b quark to hadronise into B[0 over s] or B[superscript 0] meson. Using an amplitude analysis, the fraction of decays proceeding via an intermediate K[superscript ⁎](892)[superscript 0] meson is measured to be 0.645 ± 0.049(stat) ± 0.049(syst) and its longitudinal polarisation fraction is 0.524 ± 0.056(stat) ± 0.029(syst). The relative branching fraction for this component is determined to be [B([bar over B][0 over s] → ψ(2S)K[superscript *](892)[superscript 0]) over B(B[superscript 0 → ψ(2S)K[superscript *](892)[superscript 0]] In addition, the mass splitting between the B[0 over s] and B[superscript 0] mesons is measured as M(B[0 over s]) − M(B[superscript 0]) = 87.45 ± 0.44(stat) ± 0.09(syst) MeV/c[superscript 2].