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 γ = 65 − 7 + 11 ° $$ \gamma =\left({65}_{-7}^{+11}\right){}^{\circ} $$ , in perfect agreement with the determination from tree-level B → DK decays. The B s 0 − B ¯ s 0 $$ {B}_s^0-{\overline{B}}_s^0 $$ mixing phase ϕ s 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 ϕ s = −(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.

Keywords

• Bottom Quarks
• CP Violation