$B_s\to f_0(980)$ form factors and $B_s$ decays into $f_0(980)$
We compute the $B_s\to f_0(980)$ transition form factors using light-cone QCD sum rules at leading order in the strong coupling constant, and also including an estimate of next-to-leading order corrections. We use the results to predict the branching fractions of the rare decay modes $B_s \to f_0 \ell^+ \ell^-$ and $B_s \to f_0 ν\bar ν$, which turn out to be ${\cal O}(10^{-7})$ ($B_s\to f_0(980)\ell^+\ell^-$, with $\ell=e,μ$), ${\cal O}(10^{-8})$ ($B_s\to f_0(980)τ^+τ^-$) and ${\cal O}(10^{-6})$($B_s\to f_0(980)ν\barν$). We also predict the branching ratio of $B_s\to J/ψf_0(980)$ decay under the factorization assumption, and discuss the role of this channel for the determination of the $B_s$ mixing phase compared to the golden mode $B_s \to J/ψϕ$. As a last application, we consider $D_s \to f_0$ form factors, providing a determination of the branching ratio of $D_s \to f_0 e^+ ν_e$.