Anatomy of $B^{0}_{s,d} \to J/\psi f_{0}(980)$

Abstract

The $B^{0}_{s}\to J/\psi f_{0}(980)$ decay offers an interesting experimental alternative to the well-known $B^{0}_{s}\to J/\psi \phi$ channel for the search of CP-violating New-Physics contributions to $B^{0}_{s}$–$\bar{B}^{0}_{s}$ mixing. As the hadronic structure of the f ₀(980) has not yet been settled, we take a critical look at the implications for the relevant observables and address recent experimental data. It turns out that the effective lifetime of $B^{0}_{s}\to J/\psi f_{0}(980)$ and its mixing-induced CP asymmetry S are quite robust with respect to hadronic effects and thereby allow us to search for a large CP-violating $B^{0}_{s}$–$\bar{B}^{0}_{s}$ mixing phase ϕ _s , which is tiny in the Standard Model. However, should small CP violation, i.e. in the range −0.1≲S≲0, be found in $B^{0}_{s}\to J/\psi f_{0}(980)$, it will be crucial to constrain hadronic corrections in order to distinguish possible New-Physics effects from the Standard Model. We point out that $B^{0}_{d}\to J/\psi f_{0}(980)$, which has not yet been measured, is a key channel in this respect and discuss the physics potential of this decay.