Probing chromomagnetic and chromoelectric couplings of the top quark using its polarization in pair production at hadron colliders

TL;DR

This paper explores how top-quark polarization measurements at hadron colliders can reveal potential anomalous chromomagnetic and chromoelectric couplings, providing a new way to test physics beyond the Standard Model.

Contribution

It introduces a method to probe anomalous top-gluon couplings using top polarization and angular distributions of decay leptons at Tevatron and LHC.

Findings

Sensitivity estimates for detecting anomalous couplings at Tevatron and LHC.

Angular asymmetries of decay leptons as probes of top polarization.

Potential to distinguish new physics effects from Standard Model predictions.

Abstract

The Tevatron, where the top quark was discovered, and the currently functional Large Hadron Collider (LHC), with copiously produced top pairs, enable a detailed study of top-quark properties. In particular, they can be used to test the couplings of the top quark to gauge bosons. Several extensions of the standard model (SM) can give rise to anomalous couplings of the top quark to gauge bosons, in particular, the gluons. In this work we examine how top-quark polarization, which is predicted to be negligibly small in the SM, can be used to measure chromomagnetic and chromoelectric couplings of the top quark to gluons. We lay special emphasis on the use of angular distributions and asymmetries of charged leptons arising from top decay as measures of top polarization and hence of these anomalous couplings. Sensitivities that may be reached at the Tevatron and the LHC are obtained.