Determination of gamma and -2beta_s from charmless two-body decays of beauty mesons

TL;DR

This paper uses recent LHCb measurements and symmetry relations to constrain the CP-violating phase gamma and the B_s mixing phase -2beta_s in charmless two-body beauty meson decays, accounting for U-spin breaking effects.

Contribution

It introduces a novel method combining time-dependent CP violation data and isospin symmetry to determine gamma and -2beta_s with consideration of U-spin breaking.

Findings

Gamma = (63.5 +7.2 -6.7) degrees at 68% probability

-2beta_s = -0.12 +0.14 -0.16 rad

Results include uncertainties from U-spin breaking effects up to 50%

Abstract

Using the latest LHCb measurements of time-dependent CP violation in the B^0_s -> K^+K^- decay, a U-spin relation between the decay amplitudes of B^0_s -> K^+K^- and B^0 -> \pi^+\pi^- decay processes allows constraints to be placed on the angle gamma of the unitarity triangle and on the B^0_s mixing phase -2\beta_s. Results from an extended approach, which uses additional inputs on B^0 -> \pi^0\pi^0 and B^+ -> \pi^+\pi^0 decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value \gamma = ( 63.5 +7.2 -6.7 ) degrees modulo 180 degrees is determined. In an alternative analysis, the value -2\beta_s = -0.12 +0.14 -0.16 rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included.