First observation of the decay B[0 over s] → ϕK *[superscript 0]

Abstract

The first observation of the decay B[0 over s] → ϕK∗[superscript 0] is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb[superscript −1] of pp collisions at √s = 7 TeV, collected with the LHCb detector. A yield of 30 ± 6 B[0 over s] → (K[superscript +]K[superscript −])(K[superscript −]π[superscript +) decays is found in the mass windows 1012.5 < M (K [superscript +] K [superscript −]) < 1026.5 MeV/c [superscript 2] and 746 < M(K [superscript −] π [superscript +]) < 1046 MeV/c [superscript 2]. The signal yield is found to be dominated by B[0 over s] → ϕK∗[superscript 0] decays, and the corresponding branching fraction is measured to be B(B[0 over s] → ϕK∗[superscript 0]) = (1.10 ± 0.24 (stat) ± 0.14 (syst) ± 0.08 (f [subscript d] /f [subscript s] )) × 10[superscript −6], where the uncertainties are statistical, systematic and from the ratio of fragmentation fractions f [subscript d] /f [subscript s] which accounts for the different production rate of B [superscript 0] and B[0 over s] mesons. The significance of B[0 over s] → ϕK∗[superscript 0] signal is 6.1 standard deviations. The fraction of longitudinal polarization in B[0 over s] → ϕK∗[superscript 0] decays is found to be f [subscript 0] = 0.51 ± 0.15 (stat) ± 0.07 (syst).