Determination of γ and -2βs from charmless two-body decays of beauty mesons

Abstract

Using the latest LHCb measurements of time-dependent CP violation in the B0 s → K + K − decay, a U-spin relation between the decay amplitudes of B0 s → K + K − and B0 → π +π − decay processes allows constraints to be placed on the angle γ of the unitarity triangle and on the B0 s mixing phase −2βs . Results from an extended approach, which uses additional inputs on B0 → π 0π 0 and B+ → π +π 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 γ = (63.5+7.2 −6.7)◦ modulo 180◦ is determined. In an alternative analysis, the value −2βs = −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