T-odd observables from anomalous $tbW$ couplings in single-top W associated production at the LHC

TL;DR

This paper explores how T-odd observables in single-top W associated production at the LHC can measure imaginary anomalous $tbW$ couplings, which could indicate CP violation or absorptive effects, with estimated sensitivity at various energies.

Contribution

It introduces specific T-odd observables sensitive to the imaginary part of $tbW$ couplings and analyzes their potential to detect CP-odd or absorptive effects at the LHC.

Findings

T-odd observables are proportional to the imaginary part of a single $tbW$ coupling.

Estimated 1-$\sigma$ limits for these observables at different LHC energies.

Potential to distinguish CP-odd couplings from absorptive effects.

Abstract

We investigate the possibility that an imaginary anomalous $tbW$ coupling can be measured in the process $pp \to tW^-X$ by means of T-odd observables. One such observable is the polarization of the top quark transverse to the production plane. Another is the asymmetry between the cross sections with a positive and with a negative value of a certain T-odd correlation constructed out of observable momenta when the top quark decays leptonically. The mean value of this correlation, which is also T-odd, is the third observable. These three T-odd observables are shown to be proportional to the imaginary part of only one of the $tbW$ anomalous couplings, the other couplings giving vanishing contributions. This imaginary part could signal either a CP-odd coupling, or an absorptive part in the effective coupling. We estimate the 1-$\sigma$ limits that might be derived in the case of each of these observables for centre-of-mass energies 7, 8, 13 and 14 TeV at the LHC.