Amplitude analysis of the ${B}_{(s)}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ decays and measurement of the branching fraction of the ${B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ decay

Abstract

The ${B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ and ${B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3 fb⁻¹. An untagged and timeintegrated amplitude analysis of B ⁰_(s)  → (K⁺π⁻)(K⁻π⁺) decays in two-body invariant mass regions of 150 MeV/c² around the K^∗0 mass is performed. A stronger longitudinal polarisation fraction in the ${B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ decay, f_L = 0.724 ± 0.051 (stat) ± 0.016 (syst), is observed as compared to f_L = 0.240 ± 0.031 (stat) ± 0.025 (syst) in the ${B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ decay. The ratio of branching fractions of the two decays is measured and used to determine $\mathrm{\mathcal{B}}\left({B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}\right)=\left(8.0\pm 0.9\left(\mathrm{stat}\right)\pm 0.4\left(\mathrm{syst}\right)\right)\times {10}^{-7}$.