LHCb CollaborationAdeva Andany, BernardoDosil Suárez, ÁlvaroFernández Albor, Víctor ManuelGallas Torreira, Abraham AntonioGarcía Pardiñas, JuliánHernando Morata, José ÁngelPlo Casasus, MáximoRomero Vidal, AntonioSaborido Silva, Juan JoséSanmartín Sedes, BraisSantamarina Ríos, CibránVázquez Regueiro, PabloVieites Díaz, María2020-04-282020-04-282015LHCb Collaboration et al. (2015). Observation of the decay B0s→ψ(2S)K+π−. Physics Letters B, 747, 484-4940370-2693http://hdl.handle.net/10347/21834The 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/c2eng©2015 CERN for the benefit of the LHCb Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3http://creativecommons.org/licenses/by/4.0/journal article10.1016/j.physletb.2015.06.0381873-2445open access