Measurement of branching fractions and polarization in B → φK(*) decays

TLDR: In this article, the decay amplitudes for the different helicity states are measured from the angular distributions of final state particles in the transversity basis. And they are shown to be consistent with zero.

Abstract: We present the first measurement of decay amplitudes in $B\ensuremath{\rightarrow}\ensuremath{\varphi}{K}^{*}$ and measurements of branching fractions in $B\ensuremath{\rightarrow}\ensuremath{\varphi}{K}^{(*)}$ decays based on $78.1\text{ }{\mathrm{f}\mathrm{b}}^{\ensuremath{-}1}$ of data recorded at the $\ensuremath{\Upsilon}(4S)$ resonance with the Belle detector at the KEKB ${e}^{+}{e}^{\ensuremath{-}}$ storage ring. The decay amplitudes for the different $\ensuremath{\varphi}{K}^{*0}$ helicity states are measured from the angular distributions of final state particles in the transversity basis. The longitudinal and transverse complex amplitudes are $|{A}_{0}{|}^{2}=0.43\ifmmode\pm\else\textpm\fi{}0.09\ifmmode\pm\else\textpm\fi{}0.04$, $|{A}_{\ensuremath{\perp}}{|}^{2}=0.41\ifmmode\pm\else\textpm\fi{}0.10\ifmmode\pm\else\textpm\fi{}0.04$, $\mathrm{arg}({A}_{\ensuremath{\parallel}})=\ensuremath{-}2.57\ifmmode\pm\else\textpm\fi{}0.39\ifmmode\pm\else\textpm\fi{}0.09$, and $\mathrm{arg}({A}_{\ensuremath{\perp}})=0.48\ifmmode\pm\else\textpm\fi{}0.32\ifmmode\pm\else\textpm\fi{}0.06$. The direct $CP$-violating asymmetries are found to be consistent with zero.