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

Abstract

Abstract The LHCb collaboration has recently reported the first observation of CP violation in the penguin-dominated $$ {B}_s^0 $$ B s 0 → K−K+ decay and further new measurements, indicating differences between the direct CP asymmetries of both the $$ {B}_s^0 $$ B s 0 → K−K+, $$ {B}_d^0 $$ B d 0 → π−K+ and the $$ {B}_d^0 $$ B d 0 → π−π+, $$ {B}_s^0 $$ 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 $$ {B}_s^0 $$ B s 0 → K−K+, $$ {B}_d^0 $$ B d 0 → π−π+ system alone, finding $$ \gamma =\left({65}_{-7}^{+11}\right){}^{\circ} $$ γ = 65 − 7 + 11 ° , in perfect agreement with the determination from tree-level B → DK decays. The $$ {B}_s^0-{\overline{B}}_s^0 $$ B s 0 − B ¯ s 0 mixing phase ϕs can be extracted from CP violation measurements in $$ {B}_s^0 $$ 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 $$ {B}_s^0 $$ 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.