Anatomy of ... decays

Abstract

Abstract

The decays B d ⁰ [arrow right]D d ^- D d ⁺ and B s ⁰ [arrow right]D s ^- D s ⁺ probe the CP-violating mixing phases d and s , respectively. The theoretical uncertainty of the corresponding determinations is limited by contributions from penguin topologies, which can be included with the help of the U-spin symmetry of the strong interaction. We analyse the currently available data for B d,s ⁰ [arrow right]D d,s ^- D d,s ⁺ decays and those with similar dynamics to constrain the involved non-perturbative parameters. Using further information from semileptonic B d ⁰ [arrow right]D d ^- +[nu] decays, we perform a test of the factorisation approximation and take non-factorisable SU(3)-breaking corrections into account. The branching ratios of the B d ⁰ [arrow right]D d ^- D d ⁺ , B s ⁰ [arrow right]D s ^- D d ⁺ and B s ⁰ [arrow right]D s ^- D s ⁺ ,B d ⁰ [arrow right]D d ^- D s ⁺ decays show an interesting pattern which can be accommodated through significantly enhanced exchange and penguin annihilation topologies. This feature is also supported by data for the B s ⁰ [arrow right]D d ^- D d ⁺ channel. Moreover, there are indications of potentially enhanced penguin contributions in the B d ⁰ [arrow right]D d ^- D d ⁺ and B s ⁰ [arrow right]D s ^- D s ⁺ decays, which would make it mandatory to control these effects in the future measurements of d and s . We discuss scenarios for high-precision measurements in the era of Belle II and the LHCb upgrade.