Determination of γ and −2[subscript βs] from charmless two-body decays of beauty mesons

Abstract

Using the latest LHCb measurements of time-dependent CP violation in the B[subscript s][superscript 0] → K[superscript +]K[superscript −] decay, a U-spin relation between the decay amplitudes of B[subscript s][superscript 0]→K[superscript +]K[superscript −] and B[superscript 0] →π[superscript +]π[superscript −] decay processes allows constraints to be placed on the angle γ of the unitarity triangle and on the B[subscript s][superscript 0] mixing phase −2[subscript βs]. Results from an extended approach, which uses additional inputs on B[superscript 0]→π[superscript 0]π[superscript 0] and B[superscript +]→π[superscript +]π[superscript 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[subscript −6.7][superscript +7.2])° modulo 180° is determined. In an alternative analysis, the value −2βs=−0.12[subscript −0.16][superscript +0.14] rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included.