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Axigluon as Possible Explanation for $p\bar{p} \to t\bar{t}$ Forward-Backward Asymmetry

Paul H. Frampton, Jing Shu, Kai Wang

TL;DR

The paper addresses the Tevatron anomaly in the top quark forward-backward asymmetry by proposing a flavor-nonuniversal chiral color model with a heavy axigluon arising from $SU(3)_A\times SU(3)_B \to SU(3)_c$. With axial couplings of opposite sign for light quarks and the top, and a specific vector-coupling pattern, the model explains the observed asymmetry via interference below the axigluon resonance and makes a distinctive rise-and-fall prediction for $A^{t}_{FB}$ as a function of $M_{t\bar{t}}$ near the resonance. A scan of the parameter space identifies viable regions, and a benchmark point illustrates the characteristic $A^{t}_{FB}$ shape, offering a discriminant from other explanations before direct axigluon discovery. The work also discusses possible extra-dimensional realizations and notes post-submission data that bolster the proposed correlations between $A^{t}_{FB}$ and $M_{t\bar{t}}$, providing a concrete target for experimental tests.

Abstract

A flavor-nonuniversal chiral color model is introduced. It is used for comparison to the recent data on $\bar{p} p \to \bar{t} t$. We concluded that the data are consistent with interpretation as an axigluon exchange within 1$σ$ and a unique rise and fall behavior is predicated with regard to the asymmetry $A^t_{FB}$ as a function of $t \bar{t}$ invariant mass, which can distinguish our model from others before one discovers the axigluon resonance. Further aspects of the model are discussed.

Axigluon as Possible Explanation for $p\bar{p} \to t\bar{t}$ Forward-Backward Asymmetry

TL;DR

The paper addresses the Tevatron anomaly in the top quark forward-backward asymmetry by proposing a flavor-nonuniversal chiral color model with a heavy axigluon arising from . With axial couplings of opposite sign for light quarks and the top, and a specific vector-coupling pattern, the model explains the observed asymmetry via interference below the axigluon resonance and makes a distinctive rise-and-fall prediction for as a function of near the resonance. A scan of the parameter space identifies viable regions, and a benchmark point illustrates the characteristic shape, offering a discriminant from other explanations before direct axigluon discovery. The work also discusses possible extra-dimensional realizations and notes post-submission data that bolster the proposed correlations between and , providing a concrete target for experimental tests.

Abstract

A flavor-nonuniversal chiral color model is introduced. It is used for comparison to the recent data on . We concluded that the data are consistent with interpretation as an axigluon exchange within 1 and a unique rise and fall behavior is predicated with regard to the asymmetry as a function of invariant mass, which can distinguish our model from others before one discovers the axigluon resonance. Further aspects of the model are discussed.

Paper Structure

This paper contains 7 sections, 8 equations, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Chiral Color with a Fourth Family
  3. Forward-Backward Asymmetry
  4. Numerical Results
  5. Discussion
  6. Notes Added
  7. Acknowledgement

Figures (3)

  • Figure 1: Contour plot for $1~\sigma$, $1.28~\sigma$ and $1.64~\sigma$ allowed parameter space in the $\theta$ - $M_G$ plane.
  • Figure 2: $A^{t}_{FB}$ vs. $M_{t\bar{t}}$ with $M_{t\bar{t}}$ integrated over each 150 GeV of $M_{t\bar{t}}$ using the benchmark point, $M_{G}=1525~$GeV, $g^q_V=-0.577g_s$ and $g^q_A=-g^t_A=-1.155g_s$. The solid line corresponds to our model with $g^{q}_{V}=g^{t}_{V}$ and dashed line is a comparison plot with $g^{q}_{V}=-g^{t}_{V}$, as explained in the text.
  • Figure 3: $A^{t}_{FB}$ vs. above/below $M_{t\bar{t}}$ edge using the benchmark point, $M_{G}=1525~$GeV, $g^q_A=-g^t_A=-1.155g_s$ and $g^{q}_{V}=g^{t}_{V}=-0.577g_s$