Towards New Frontiers in the Exploration of Charmless Non-Leptonic $B$ Decays

Abstract

Non-leptonic $B$ decays into charmless final states offer an important laboratory to study CP violation and the dynamics of strong interactions. Particularly interesting are $B^0_s\to K^-K^+$ and $B^0_d\toπ^-π^+$ decays, which are related by the $U$-spin symmetry of strong interactions, and allow for the extraction of CP-violating phases and tests of the Standard Model. The theoretical precision is limited by $U$-spin-breaking corrections and innovative methods are needed in view of the impressive future experimental precision expected in the era of Belle II and the LHCb upgrade. We have recently proposed a novel method to determine the $B_s^0$-$\bar{B}_s^0$ mixing phase $ϕ_s$ from the $B_s^0\to K^-K^+$, $B_d^0\to π^-π^+$ system, where semileptonic $B^0_s\to K^-\ell^+ν_\ell$, $B^0_d\to π^-\ell^+ν_\ell$ decays are a new ingredient and the theoretical situation is very favourable. We discuss this strategy in detail, with a focus on penguin contributions as well as exchange and penguin-annihilation topologies which can be probed by a variety of non-leptonic $B$ decays into charmless final states. We show that a theoretical precision as high as ${\cal O}(0.5^\circ)$ for $ϕ_s$ can be attained in the future, thereby offering unprecedented prospects for the search for new sources of CP violation.