Measurement of the CP-violation parameter of B⁰ mixing and decay with pp̅ →µµX data

Abstract

We measure the dimuon charge asymmetry A in pp̅ collisions at a center of mass energy √s=1960 GeV. The data was recorded with the D0 detector and corresponds to an integrated luminosity of approximately 1.0 fb⁻¹. Assuming that the asymmetry A is due to asymmetric B⁰↔B̅ ⁰ mixing and decay, we extract the CP-violation parameter of B⁰ mixing and decay: ℜ εB⁰)/1+|εB⁰|²=A_B⁰/4= -0.0023±0.0011(stat)±0.0008(syst).A_B⁰ is the dimuon charge asymmetry from decays of B⁰B̅⁰ pairs.The general case, with CP violation in both B⁰ and B₂⁰systems, is also considered. Finally we obtain the forward-backward asymmetry that quantifies the tendency of μ⁺ to go in the proton direction and μ^- to go in the antiproton direction. The results are consistent with the standard model and constrain new physics.