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

TL;DR

This paper calculates transition form factors for $B_{(s)}$ decays into scalar mesons using light-cone sum rules, predicts decay rates and polarization asymmetries, and suggests these can help understand scalar meson structures.

Contribution

It provides new form factor estimates in the light-cone sum rules approach, which are about twice as large as previous models, and analyzes decay rates and asymmetries for scalar meson semileptonic decays.

Findings

Form factors are approximately twice as large as previous estimates.

Certain decay channels have branching ratios around 10^{-4}.

Lepton polarization asymmetries are close to -1 for electrons and muons.

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.