Measurement of the B0s→J/ψ¯¯¯¯K*0 branching fraction and angular amplitudes

Abstract

A sample of 114±11 B0s→J/ψK−π+ signal events obtained with 0.37 fb−1 of pp collisions at √s=7 TeV collected by the LHCb experiment is used to measure the branching fraction and polarization amplitudes of the B0s→J/ψ¯¯¯¯K*0 decay, with ¯¯¯¯K*0→K−π+. The K−π+ mass spectrum of the candidates in the B0s peak is dominated by the ¯¯¯¯K*0 contribution. Subtracting the nonresonant K−π+ component, the branching fraction of B0s→J/ψ¯¯¯¯K*0 is (4.4+0.5−0.4±0.8)×10−5, where the first uncertainty is statistical and the second is systematic. A fit to the angular distribution of the decay products yields the K*0 polarization fractions fL=0.50±0.08±0.02 and f∥=0.19+0.10−0.08±0.02.