Observation of the decay B0s→ψ(2S)K+π−

Abstract

The decay B0s→ψ(2S)K+π−is observed using a data set corresponding to an integrated luminosity of 3.0fb−1collected by the LHCb experiment in ppcollisions at centre-of-mass energies of 7 and 8 TeV. The branching fraction relative to the B0→ψ(2S)K+π−decay mode is measured to be B(B0s→ψ(2S)K+π−)B(B0→ψ(2S)K+π−)=5.38±0.36(stat)±0.22(syst)±0.31(fs/fd)%, where fs/fdindicates the uncertainty due to the ratio of probabilities for a bquark to hadronise into a B0sor B0meson. Using an amplitude analysis, the fraction of decays proceeding via an intermediate K∗(892)0meson 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(B0s→ψ(2S)K∗(892)0)B(B0→ψ(2S)K∗(892)0)=5.58±0.57(stat)±0.40(syst)±0.32(fs/fd)%. In addition, the mass splitting between the B0sand B0mesons is measured as M(B0s)−M(B0)=87.45±0.44(stat)±0.09(syst)MeV/c2