New color-octet axial vector boson revisited

Abstract

In this paper we re-examine how to utilize the previous proposed color-octet axial-vector boson $Z_{\mathrm{C}}$ to explain the $3.4\sigma$ anomaly of $t\bar{t}$ forward-backward (FB) asymmetry $A_{\mathrm{FB}}$ 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 $M_{\mathrm{C}}=440\text{GeV}$, 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 $Z_{\mathrm{C}}$.

Comments: 16 pages, 5 figures, published version in PRD