We report the measurements of branching fractions and CP violation asymmetries in $B^0 \to \phi K^{ *}$ decays obtained in an angular analysis using the full data sample of $772 \times 10^6 B\bar{ B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We perform a partial wave analysis to distinguish among scalar [$B^0 \to \phi(K\pi)^{ *}_{ 0}$], vector [$B^0 \to \phi K^{ *}(892)^{ 0}$] and tensor [$B^0 \to \phi K^{ *}_{ 2}(1430)^{ 0}$] 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 $\mathcal{ B}[B^0 \to \phi K^{ *}_{ 2}(1430)^{ 0}] = (5.5 ^{ +0.9}_{ -0.7} \pm 1.0) \times 10^{ -6}$. We also measure the longitudinal polarization fraction $f_L$ 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 $0.918 ^{ +0.029}_{ -0.060} \pm 0.012$, 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 $B^0 \to \phi K^{ *}$ system. No evidence for CP violation is found.
Categories: hep-ex