Model independent analysis of the forward-backward asymmetry of top quark production at the Tevatron

Abstract

Motivated by a possible anomaly in the forward-backward (FB) asymmetry of top quark (A_{\rm FB}) observed at the Tevatron, we perform a model independent analysis on q \bar{q} \to t \bar{t} using an effective lagrangian with dim-6 four-quark operators. We derive necessary conditions on new physics structures and the couplings that are consistent with the t\bar{t} production cross section and A_{\rm FB} measured at the Tevatron, and discuss possible new physics scenarios that could generate such dim-6 operators.

Figures (3)

• Figure 1: The region in $( C_1 , C_2 )$ plane that is consistent with the Tevatron data at the $1 \sigma$ level: $\sigma_{t\bar{t}} = (7.50 \pm 0.48)$ pb and $A_{\rm FB} = (0.24 \pm 0.13 \pm 0.04)$. Also shown are the boundaries of the validity regions described in the text taking $r=0.3$ (magenta), $0.5$ (blue) and $1$ (black). The straight lines are from the inequality Eq. (4), the circles and their mirror images from the inequality Eq. (5), and the ellipses centered at the origin from Eq. (6).
• Figure 2: (a) The $M_{t\bar{t}}$ distribution for the points I,II,III, IV and the SM and (b) the spin-spin correlations $C$ and $C_{FB}$.
• Figure 3: The 1-$\sigma$ favored region of the couplings for the exchanges of the spin-1 FC color-octet vector bosons $V_8$.