Forward-Backward Asymmetry in Top Quark Production in ppbar Collisions at sqrt{s}=1.96 TeV

TL;DR

Measurements of the forward-backward charge asymmetry in top pair production using 1.96 TeV recorded with the Collider Detector at Fermilab II show values consistent with the standard model expectation and disfavor exotic production mechanisms with significant negative values.

Abstract

Reconstructable final state kinematics and charge assignment in the reaction ppbar->ttbar allows tests of discrete strong interaction symmetries at high energy. We define frame dependent forward-backward asymmetries for the outgoing top quark in both the ppbar and ttbar rest frames, correct for experimental distortions, and derive values at the parton-level. Using 1.9/fb of ppbar collisions at sqrt{s}=1.96 TeV recorded with the CDF II detector at the Fermilab Tevatron, we measure forward-backward top quark production asymmetries in the ppbar and ttbar rest frames of A_{FB,pp} = 0.17 +- 0.08 and A_{FB,tt} = 0.24 +- 0.14.

Figures (1)

• Figure 1: The two top quark production angle variables, $\cos\theta$ for the ${ p} \bar{{ p}}$ frame and $\Delta Y$ for the $t\bar{t}$ frame. The solid line is the prediction for $t\bar{t}$ with mc@nlo model of the QCD induced charge asymmetry and $\sigma_{t\bar{t}}=8.2$ pb, plus the expected non-$t\bar{t}$ backgrounds. The dashed curve shows the prediction when $t\bar{t}$ is reweighted according to the form $1 + A_\mathrm{FB}\cos\alpha$ using measured values of $A_\mathrm{FB}$.