Measurement of the CP-violation parameter of B^0 mixing and decay with pp(bar) -> mu mu X data

TL;DR

This paper measures the CP-violation parameter in B^0 meson mixing and decay using dimuon charge asymmetry data from proton-antiproton collisions, providing results consistent with the Standard Model and constraining new physics.

Contribution

It presents the first measurement of the CP-violation parameter in B^0 mixing and decay from pp̄ collisions at 1960 GeV, using dimuon charge asymmetry data.

Findings

Measured the CP-violation parameter as -0.0023 +/- 0.0011 (stat) +/- 0.0008 (syst)

Results are consistent with the Standard Model predictions

Constrained possible new physics contributions to B^0 mixing and decay

Abstract

We measure the dimuon charge asymmetry A in pp(bar) collisions at a center of mass energy sqrt{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 B^0 <-> B(bar)^0 mixing and decay, we extract the CP-violation parameter of B^0 mixing and decay: Re(epsilon_B^0)(1 + |epsilon_B^0|^2) = A_B^0/4 = -0.0023 +/- 0.0011 (stat) +/- 0.0008 (syst). A_B^0 is the dimuon charge asymmetry from decays of B^0 B(bar)^0 pairs. The general case, with CP violation in both B^0 and B_s^0 systems, is also considered. Finally we obtain the forward-backward asymmetry that quantifies the tendency of mu+ to go in the proton direction and mu- to go in the anti-proton direction. The results are consistent with the standard model and constrain new physics.