Zooming into CP violation in B(s)→ hh decays

Abstract

The LHCb collaboration has recently reported the first observation of CP violation in the penguin-dominated {B}_s^0 → K−K+ decay and further new measurements, indicating differences between the direct CP asymmetries of both the {B}_s^0 → K−K+, {B}_d^0 → π−K+ and the {B}_d^0 → π−π+, {B}_s^0 → K−π+ modes. We show that these puzzling differences can be accommodated through sizeable penguin annihilation and exchange topologies in the Standard Model, and constrain them. Utilising the U-spin symmetry, we extract the angle γ of the unitarity triangle from the CP asymmetries in the {B}_s^0 → K−K+, {B}_d^0 → π−π+ system alone, finding gamma =left({65}_{-7}^{+11}right){}^{circ} , in perfect agreement with the determination from tree-level B → DK decays. The {B}_s^0-{overline{B}}_s^0 mixing phase ϕs can be extracted from CP violation measurements in {B}_s^0 → K−K+ in a clean way. We present a new strategy and extract ϕs = −(3.6 ± 5.4)°. This result is in agreement with the determination from {B}_s^0 → J/ψϕ decays. New CP-violating contributions would influence these determinations differently. Hence it is interesting to keep monitoring both as the experimental picture sharpens.