CP asymmetries in $B\to \pi^{+}\pi^{-} K_S,\, K^{+} K^{-} K_S$ Decays in the $f_0(980)$ Mass Region

We consider the branching ratios and direct and time-dependent asymmetries in $B\to f_0(980) K_S \to (\pi^+\pi^- ,K^+ K^- ) K_S$ decays %in the $f_0(980)$ %mass region to the end of determining the deviation of the time-dependent asymmetry from $\sin(2\beta)$ arising from Standard Model physics. We construct the $f_0(980)$ from isospin-zero $\pi^+\pi^-$ and $K^+K^-$ final states, employing scalar form factors consistent with chiral constraints at low energies and utilize QCD factorization for the $B\to f_0(980) K_S$ decay amplitudes.