Measurement of CP asymmetries and polarisation fractions in B<inf>s</inf>⁰→K^∗0K^¯∗0 decays

Abstract: An angular analysis of the decay B _s ⁰→K ^∗0K ^¯∗0 is performed using pp collisions corresponding to an integrated luminosity of 1.0 fb ⁻¹ collected by the LHCb experiment at a centre-of-mass energy √s=7 TeV. A combined angular and mass analysis separates six helicity amplitudes and allows the measurement of the longitudinal polarisation fraction f _L = 0.201 ± 0.057 (stat.) ± 0.040 (syst.) for the (Formula Presented) decay. A large scalar contribution from the K ₀ ^∗(1430) and K ₀ ^∗(800) resonances is found, allowing the determination of additional CP asymmetries. Triple product and direct CP asymmetries are determined to be compatible with the Standard Model expectations. The branching fraction ℬBs→ ^{K∗ 8920 K¯∗ 8920} is measured to be (10.8 ± 2.1 (stat.) ± 1.4 (syst.) ± 0.6 (f _d/f _s)) × 10 ⁻⁶.