First measurement of the forward-backward asymmetry in bottom-quark pair production at high mass

TL;DR

This paper reports the first measurement of the forward-backward asymmetry in bottom-quark pair production at high mass, using proton-antiproton collision data, and compares results with standard model predictions and new physics models.

Contribution

It provides the first experimental measurement of the asymmetry at high mass and tests specific new physics models involving axigluons.

Findings

Asymmetry consistent with zero and standard model predictions

Disfavors a 200 GeV/c^2 axigluon model

Does not exclude a 345 GeV/c^2 axigluon model

Abstract

We measure the particle-level forward-backward production asymmetry in $b\bar{b}$ pairs with masses $m(b\bar{b})$ larger than 150 GeV/$c^2$, using events with hadronic jets and employing jet charge to distinguish $b$ from $\bar{b}$. The measurement uses 9.5/fb of ppbar collisions at a center of mass energy of 1.96 TeV recorded by the CDF II detector. The asymmetry as a function of $m(b\bar{b})$ is consistent with zero, as well as with the predictions of the standard model. The measurement disfavors a simple model including an axigluon with a mass of 200 GeV/$c^2$ whereas a model containing a heavier 345 GeV/$c^2$ axigluon is not excluded.