Measurement of the B0s→J/ψK∗0 branching fraction and angular amplitudes

A search for the decay B0s→J/ψK∗0 with K∗0→K−π+ is performed with 0.37 fb−1 of pp collisions at s√ = 7 TeV collected by the LHCb experiment, finding a \Bs→JψK−π+ peak of 114±11 signal events. The K−π+ mass spectrum of the candidates in the B0s peak is dominated by the K∗0 contribution. Subtracting the non-resonant K−π+ component, the branching fraction of \BsJpsiKst is (4.4+0.5−0.4±0.8)×10−5, where the first uncertainty is statistical and the second systematic. A fit to the angular distribution of the decay products yields the \Kst polarization fractions fL=0.50±0.08±0.02 and f∣∣∣∣=0.19+0.10−0.08±0.02.