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Probing anomalous top quark interactions at the Fermilab Tevatron Collider

Ken-ichi Hikasa, K. Whisnant, Jin Min Yang, Bing-Lin Young

TL;DR

The paper uses an effective field theory with dimension-six operators to parameterize anomalous top-quark interactions at the Fermilab Tevatron, focusing on the $gt\bar t$ and $Wt\bar b$ vertices. It derives Run 1 bounds from top-pair cross sections and projects Run 2/3 sensitivity, showing that future data can significantly tighten limits or reveal new physics effects. Two concrete disentangling strategies are proposed: energy-dependent distortions in the $t\bar t$ invariant-mass spectrum and a top-quark polarization asymmetry, enabling separation of operators with overlapping signatures. The analysis also evaluates single-top production, finds strong $R_b$ constraints for several operators, and identifies the remaining operators that Tevatron Run 2/3 can meaningfully probe, with implications for the scale $\Lambda$ of new physics.

Abstract

We study the effects of dimension-six operators contributing to the $gt\bar t$ vertex in top quark pair production at the Tevatron collider. We derive both the limits from Run 1 data and the potential bounds from future runs (Run 2 and 3). Although the current constraints are not very strong, the future runs are quite effective in probing these operators. We investigate the possibility of disentangling different operators with the $t\bar t$ invariant mass distribution and the top quark polarization asymmetry. We also study the effects of a different set of operators contributing to single top production via the $Wt\bar b$ coupling. We derive the current and potential future bounds on these anomalous operators and find that the upgraded Tevatron can improve the existing constraints from $R_b$ for one of the operators.

Probing anomalous top quark interactions at the Fermilab Tevatron Collider

TL;DR

The paper uses an effective field theory with dimension-six operators to parameterize anomalous top-quark interactions at the Fermilab Tevatron, focusing on the and vertices. It derives Run 1 bounds from top-pair cross sections and projects Run 2/3 sensitivity, showing that future data can significantly tighten limits or reveal new physics effects. Two concrete disentangling strategies are proposed: energy-dependent distortions in the invariant-mass spectrum and a top-quark polarization asymmetry, enabling separation of operators with overlapping signatures. The analysis also evaluates single-top production, finds strong constraints for several operators, and identifies the remaining operators that Tevatron Run 2/3 can meaningfully probe, with implications for the scale of new physics.

Abstract

We study the effects of dimension-six operators contributing to the vertex in top quark pair production at the Tevatron collider. We derive both the limits from Run 1 data and the potential bounds from future runs (Run 2 and 3). Although the current constraints are not very strong, the future runs are quite effective in probing these operators. We investigate the possibility of disentangling different operators with the invariant mass distribution and the top quark polarization asymmetry. We also study the effects of a different set of operators contributing to single top production via the coupling. We derive the current and potential future bounds on these anomalous operators and find that the upgraded Tevatron can improve the existing constraints from for one of the operators.

Paper Structure

This paper contains 13 sections, 37 equations, 2 figures, 3 tables.

Table of Contents

  1. Introduction
  2. List of the relevant operators
  3. Top pair total cross section
  4. Anomalous contribution to top pair production cross section
  5. Current bounds from Run 1
  6. Expectations for Run 2 and 3
  7. Disentangling different operators
  8. $t\bar{t}$ invariant mass distribution
  9. Top polarization asymmetry
  10. Single top quark production
  11. Signal and backgrounds
  12. Improvement of the bounds with Run 2 and 3
  13. Conclusions

Figures (2)

  • Figure 1: Top pair invariant mass distribution in the SM (solid), with contributions from $O_{tG\Phi}$ (dashed) and with $O_{tG}$ and/or $O_{qG}$ (dotted and dash-dotted). The two curves for $O_{tG}/O_{qG}$ correspond to different coupling strengths.
  • Figure 2: The ratio $R$ with $M_0=600$ GeV as a function of $(C_{tG}+C_{qG})/\Lambda^2$. The SM value is indicated by the dashed line.