New color-octet axial vector boson revisited

TL;DR

This paper re-examines the potential of a color-octet axial-vector boson to explain the top quark forward-backward asymmetry anomaly, fitting parameters to recent data and exploring its effects at the LHC.

Contribution

It provides a revised analysis of the $Z_C$ boson model, identifying best-fit parameters and proposing $A_{OFB}$ as a measurable signature at the LHC.

Findings

Best-fit parameters: $g_A^q=0.07$, $g_A^Q=3$, $M_C=440$ GeV.

$A_{OFB}$ can be used to measure properties of $Z_C$ at the LHC.

The model explains the $A_{FB}$ anomaly with specific axial couplings.

Abstract

In this paper we re-examine how to utilize the previous proposed color-octet axial-vector boson $Z_{\rm C}$ to explain the $3.4\sigma$ anomaly of $t\bar t$ forward-backward (FB) asymmetry $A_{\rm FB}$ for $m_{t\bar t}> 450$GeV observed by CDF. Our numerical results indicate that the best-fit parameters are $g_A^q=0.07$, $g_A^Q=3$, and $M_{\rm C}=440\text{GeV}$, which are obtained by fitting the mass dependent $A_{\rm FB}$ and total cross section data provided by a recent CDF measurement. Here $g_A^q (g_A^Q)$ and $M_{\rm C}$ are the axial couplings among $Z_{\rm C}$ with the first two (the third) generation quarks, and $Z_{\rm C}$ mass respectively. We also calculate one-side forward-backward asymmetry $A_{\rm OFB}$ for top and bottom quark pair production at the LHC, focusing on the new contributions from $Z_{\rm C}$. Our studies show that $A_{\rm OFB}$ can be utilized to measure the properties of new particle $Z_{\rm C}$.