$B\to \eta^{(\prime)} (\ell^{-} \bar\nu_{\ell}, \ell^{+} \ell^{-}, K, K^*)$ decays in the quark-flavor mixing scheme

Abstract

In the quark-flavor mixing scheme, $\eta$ and $\eta'$ are linear combinations of flavor states $\eta_{q}=(u\bar{u}+d\bar{d})/\sqrt{2}$ and $\eta_{s}=s\bar{s}$ with the masses of $m_{qq}$ and $m_{ss}$, respectively. Phenomenologically, $m_{ss}$ is strictly fixed to be around 0.69, which is close to $\sqrt{2m^{2}_{K}-m^{2}_{\pi}}$ by the approximate flavor symmetry, while $m_{qq}$ is found to be $0.18\pm 0.08$ GeV. For a large allowed value of $m_{qq}$, we show that the BRs for $B\to \eta^{(\prime)} X$ decays with $X=(\ell^{-} \bar\nu_{\ell}, \ell^{+} \ell^{-})$ are enhanced. We also illustrate that $BR(B\to\eta X)> BR(B\to \eta^{\prime} X)$ in the mechanism without the flavor-singlet contribution. Moreover, we demonstrate that the decay branching ratios (BRs) for $B\to \eta^{(\prime)}K^{[*]}$ are consistent with the data. In particular, the puzzle of the large $BR(B\to \eta^{\prime} K)$ can be solved. In addition, we find that the CP asymmetry for $B^{\pm}\to \eta K^{\pm}$ can be as large as -30%, which agrees well with the data. However, we cannot accommodate the CP asymmetries of $B\to \eta K^*$ in our analysis, which could indicate the existence of some new CP violating sources.