Evidence for an anomalous like-sign dimuon charge asymmetry

TL;DR

This paper reports the first evidence of anomalous CP-violation in neutral B meson mixing, based on a precise measurement of like-sign dimuon charge asymmetry in proton-antiproton collisions, showing a significant deviation from the Standard Model prediction.

Contribution

It provides the first experimental evidence of anomalous CP-violation in B meson mixing through a detailed measurement of dimuon charge asymmetry.

Findings

Measured like-sign dimuon charge asymmetry $ ext{A}$ with high precision.

Found a 3.2 sigma deviation from the Standard Model prediction.

Indicates potential new physics beyond the Standard Model.

Abstract

We measure the charge asymmetry $A$ of like-sign dimuon events in 6.1 fb$^{-1}$ of $p\bar{p}$ collisions recorded with the D0 detector at a center-of-mass energy $\sqrt{s} = 1.96$ TeV at the Fermilab Tevatron collider. From $A$, we extract the like-sign dimuon charge asymmetry in semileptonic $b$-hadron decays: $\aslb = -0.00957 \pm 0.00251 ({\rm stat}) \pm 0.00146 ({\rm syst})$. This result differs by 3.2 standard deviations from the standard model prediction $\aslb(SM) = (-2.3^{+0.5}_{-0.6}) \times 10^{-4}$ and provides first evidence of anomalous CP-violation in the mixing of neutral $B$ mesons.