Study of scalar meson $f_0(980)$ from $B\to f_0(980)K^{\ast }$ Decays

In this paper, the branching ratios and the direct CP-violating asymmetries for decays ${\bar{B}}^0\to f_0(980){\bar{K}}^{\ast 0}$ and $B^{-}\to f_0(980)K^{\ast -}$ by employing the perturbative QCD factorization approach are studied. In the two-quark model supposition, $f_0(980)$ is commonly viewed as a mixture of $s\bar{s}$ and $n\bar{n}(\equiv (u\bar{u}+d\bar{d})\mathrm{/}\sqrt{2})$, that is $\mathrm{\mid }{f}_0(980)\text{ra}=\mathrm{\mid }s\bar{s}\text{ra}\cos \theta +\mathrm{\mid }n\bar{n}\text{ra}\sin \theta$, where $\theta$ is the $f_0-\sigma$ mixing angle. We find that the non-factorizable $f_0$ emission type diagrams can give large contributions to the final results, which are consistent with the present experimental data and the upper limit in the allowed mixing angle ranges. We predict that the direct CP asymmetry ${\cal A}^{dir}_{CP}(f_0(980)\bar K^{*0})$ is small, only a few percent, which can be tested by future B factory experiments.