$B_s (\bar B_s)$ -> $D^0_{CP} K {\bar K}$: Detecting and Discriminating New Physics in $B_s$-$\bar B_s$ Mixing

Abstract

If the weak phase of B_s-anti B_s mixing (2 beta_s) is found to be significantly different from zero, this is a clear signal of new physics (NP). However, if such a signal is found, we would like an unambiguous determination of 2 beta_s in order to ascertain which NP models could be responsible. In addition, in the presence of NP, the width difference ΔΓ_s between the two B_s mass eigenstates can be positive or negative, and ideally this sign ambiguity should be resolved experimentally. Finally, in order to see if the NP is contributing to Γ^s_{12} in addition to M^s_{12}, the precise measurement of |Γ^s_{12}| is crucial. In this paper, we consider several different methods of measuring B_s-anti B_s mixing using two- and three-body decays with ${\bar b} \to {\bar c} u {\bar s}$ and ${\bar b} \to {\bar u} c {\bar s}$ transitions. We find that the most promising of these is a time-dependent Dalitz-plot analysis of $B_s (\bar B_s) \to D^0_{CP} K {\bar K}$. With these decays, all of the above issues can be addressed, and the measurement of the weak phase gamma is also possible. We also note that, with all three-body decays it is possible to resolve the sign ambiguity of ΔΓ_s even without determining the CP phase phi_s.