Measurement of the anomalous like-sign dimuon charge asymmetry with 9 fb^-1 of p pbar collisions

TL;DR

This paper reports an updated measurement of the like-sign dimuon charge asymmetry in proton-antiproton collisions, revealing a significant deviation from the Standard Model prediction and indicating possible new sources of CP violation in B-hadron decays.

Contribution

The study provides the most precise measurement to date of the asymmetry, showing a 3.9 sigma deviation from the Standard Model, suggesting evidence for new physics in CP violation.

Findings

Aslb = (-0.787 +- 0.172 (stat) +- 0.093 (syst))%

Deviation from Standard Model by 3.9 standard deviations

Asymmetry consistent with origin from semi-leptonic b-hadron decays

Abstract

We present an updated measurement of the anomalous like-sign dimuon charge asymmetry Aslb for semi-leptonic $b$-hadron decays in 9.0 fb^-1 of p pbar collisions recorded with the D0 detector at a center-of-mass energy of sqrt{s} = 1.96 TeV at the Fermilab Tevatron collider. We obtain Aslb = (-0.787 +- 0.172(stat) +- 0.093 (syst))%. This result differs by 3.9 standard deviations from the prediction of the standard model and provides evidence for anomalously large CP violation in semi-leptonic neutral B decay. The dependence of the asymmetry on the muon impact parameter is consistent with the hypothesis that it originates from semi-leptonic b-hadron decays.