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

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.