New color-octet axial vector boson revisited

Abstract

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