T-odd observables from anomalous $tbW$ couplings in single-top production at an $ep$ collider

TL;DR

This paper explores how T-odd observables in single-top production at an ep collider can measure imaginary anomalous tbW couplings, providing potential signals of CP violation or absorptive effects.

Contribution

It introduces T-odd observables sensitive to the imaginary part of anomalous tbW couplings in ep collisions, highlighting their potential to detect CP-odd or absorptive effects.

Findings

T-odd observables are proportional to the imaginary part of a specific anomalous coupling.

Estimated 1-sigma limits for different collider energies.

Potential to distinguish CP-odd and absorptive effects.

Abstract

We investigate the possibility that an imaginary anomalous $tbW$ coupling can be measured in the process $e^-p \to \nu_e \overline t X$ by means of T-odd observables. One such observable considered here is the polarization of the top antiquark transverse to the production plane. The other is a T-odd correlation constructed out of observable momenta when the top quark decays leptonically. Both these T-odd observables are shown to be proportional to the imaginary part of only one of the $tbW$ anomalous couplings, the other couplings giving either vanishing or negligible contribution. This imaginary part could signal either a CP-odd coupling, or an absorptive part in the effective coupling, or both. We estimate the 1-$\sigma$ limits that might be derived in the case of each of these observables for a collider with a proton energy of 7 TeV and an electron energy of 60 GeV and also in the case of a higher electron energy of 150 GeV.