Zooming into CP violation in $B_{(s)}\to hh$ Decays

TL;DR

This paper analyzes CP violation in B meson decays, demonstrating how Standard Model effects can explain observed differences, and introduces new methods to extract key parameters like the unitarity triangle angle and mixing phase with consistency checks.

Contribution

It provides a novel analysis of CP violation in B decays using U-spin symmetry, constrains penguin topologies, and proposes new strategies for measuring the mixing phase $\

Findings

Standard Model penguin effects can explain CP asymmetry differences.

Extracted unitarity angle $\

Determined the $B_s$--$ar B_s$ mixing phase $\

Abstract

The LHCb collaboration has recently reported the first observation of CP violation in the penguin-dominated $B^0_s\to K^-K^+$ decay and further new measurements, indicating differences between the direct CP asymmetries of both the $B^0_s\to K^-K^+$, $B^0_d\to\pi^-K^+$ and the $B^0_d\to \pi^-\pi^+$, $B^0_s\to K^-\pi^+$ 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 $\gamma$ of the unitarity triangle from the CP asymmetries in the $B^0_s\to K^-K^+$, $B^0_d\to \pi^-\pi^+$ system alone, finding $\gamma=(65^{+11}_{-7})^\circ$, in perfect agreement with the determination from tree-level $B\to DK$ decays. The $B^0_s$--$\bar B^0_s$ mixing phase $\phi_s$ can be extracted from CP violation measurements in $B^0_s\to K^-K^+$ in a clean way. We present a new strategy and extract $\phi_s=-(3.6\pm 5.4)^\circ$. This result is in agreement with the determination from $B^0_s\to J/\psi \phi$ decays. New CP-violating contributions would influence these determinations differently. Hence it is interesting to keep monitoring both as the experimental picture sharpens.