Angular analysis of $B^0\to \varphi K^{\ast }$ decays and search for CP violation at Belle

We report the measurements of branching fractions and CP violation asymmetries in $B^0\to \varphi K^{\ast }$ decays obtained in an angular analysis using the full data sample of $772\times {10}^{6}B\bar{B}$ pairs collected at the $\mathrm{{\rm Y}}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We perform a partial wave analysis to distinguish among scalar [$B^0\to \varphi (K\pi {)}_0^{\ast }$], vector [$B^0\to \varphi K^{\ast }(892{)}^0$] and tensor [$B^0\to \varphi K_2^{\ast }(1430{)}^0$] components, and determine the corresponding branching fractions to be $$\mathcal{B}$[B^0 \to \phi(K\pi)^{}_{0}] = (4.3 \pm 0.4 \pm 0.4) \times 10^{-6}$,$$\mathcal{B}$[B^0 \to \phi K^{}(892)^{0}] = (10.4 \pm 0.5 \pm 0.6) \times 10^{-6}$and$$\mathcal{B}$[B^0 \to \phi K^{}{2}(1430)^{0}] = (5.5 ^{+0.9}{-0.7} \pm 1.0) \times 10^{-6}$\mathrm{.}Wealsomeasurethelongitudinalpolarizationfraction$f_L$in$B^0 \to \phi K^{}(892)^{0}$and$B^0 \to \phi K^{*}_{2}(1430)^{0}$ decays to be $0.499\pm 0.030\pm 0.018$ and $0.918_{-0.060}^{+0.029}\pm 0.012$, respectively. The first quoted uncertainties are statistical and the second are systematic. In total, we measure 26 parameters related to branching fractions, polarization and CP violation in the $B^0\to \varphi K^{\ast }$ system. No evidence for CP violation is found.