Scalar mesons in weak semileptonic decays of $B_{(s)}$

Abstract

The transition form factors of $B_{(s)} \to S$, with $S$ denoting a scalar meson, are investigated in the light-cone sum rules approach. The numerical values are approximately twice as large as that estimated in the light-front quark model and QCD sum rules approach. Using these form factors, we present the analysis of the decay rates for $B \to a_0(1450) l \bar{\nu}_l $, $B \to K^{\ast}_0(1430) l \bar{l}$, $B_s \to K^{\ast}_0(1430) l \bar{\nu}_l$ and $B_s \to f_0(1500) l \bar{l}$ with $l=e, \mu, \tau$. The results indicate that magnitudes of $BR(\bar{B}_0 \to a_0(1450) l \bar{\nu}_l)$ and $BR(B_s \to K^{\ast}_0(1430) l \bar{\nu}_l)$ can arrive at the order of $10^{-4}$, which can be measured in the future experiments to clarify the inner structure of scalar mesons. It is also observed that $BR(B \to K^{\ast}_0(1430) \tau^+ \tau^-)$ and $BR(B_s \to f_0(1500) \tau^+ \tau^-)$ are an order of magnitude smaller than the corresponding channels of $e^+ e^-$ and $\mu^+ \mu^-$ final states due to the heavily suppressed phase space . Moreover, the longitudinal lepton polarization asymmetry for $B \to K^{\ast}_0(1430) l \bar{l}$ and $B_s \to f_0(1500) l \bar{l}$ are also investigated, whose values are close to -1 for the $e^+ e^-$ and $\mu^+ \mu^-$ pair except the region close to the end points.