Probing the Anomalous Couplings of the Top Quark with Gluon at the LHC and Tevatron

TL;DR

This paper investigates how anomalous top quark couplings to gluons, specifically chromoelectric and chromomagnetic dipole moments, affect top pair production rates and asymmetries at the LHC and Tevatron, providing bounds on these couplings.

Contribution

It introduces a detailed analysis of the sensitivity of top pair production observables to anomalous couplings, deriving new bounds on CEDM and CMDM from experimental data.

Findings

Non-zero CMDM can suppress top pair production rates.

The ratio of gluon-gluon to quark-antiquark top pair production is highly sensitive to anomalous couplings.

Combined measurements impose stringent limits on CEDM and CMDM.

Abstract

In this paper, we study the sensitivity of the fraction of $t\bar{t}$ events arising from gluon-gluon fusion to the chromoelectric and chromomagnetic dipole moments (CEDM and CMDM) as well as the total and differential $t\bar{t}$ cross sections at the LHC and Tevatron. The sensitivity of measured charged asymmetry at the LHC to CEDM and CMDM is also studied. We find that at the Tevatron and the LHC, non-zero values of CMDM could suppress the $t\bar{t}$ production rate. It is shown that the ratio of $\sigma(gg\rightarrow t\bar{t})/\sigma(p\bar{p}\rightarrow t\bar{t})$ at the Tevatron is more sensitive to CEDM and CMDM than the LHC case. The presence of CEDM always increases the contribution of gluon-gluon fusion process in top pair rate at the Tevatron and LHC. Except for a small range of CMDM, the presence of CEDM and CMDM can increase the fraction of gluon-gluon fusion at the Tevatron and LHC. The measured ratio of $\sigma(gg\rightarrow t\bar{t})/\sigma(p\bar{p}\rightarrow t\bar{t})$ at the Tevatron is used to derive bounds on the chromoelectric and chromomagnetic dipole moments as well as the total and differential ($d\sigma/dm_{t\bar{t}}$) cross sections at the LHC and Tevatron, and the measured charged asymmetry at the LHC. The combination of $d\sigma_{TeV}/dm_{t\bar{t}}$ and $\sigma_{LHC}$ provides stringent limits on CMDM and CEDM.