Top-spin analysis of new scalar and tensor interactions in e^+ e^- collisions with beam polarization

TL;DR

This paper demonstrates how top polarization in e+ e- collisions at the ILC can significantly improve the sensitivity to new scalar and tensor interactions beyond the standard model, using beam polarization and spin-momentum correlations.

Contribution

It introduces a model-independent framework utilizing top polarization to probe and disentangle scalar and tensor interactions in e+ e- collisions, with improved sensitivity estimates.

Findings

Sensitivity to scalar and tensor couplings of a few times 10^{-3} TeV^{-2} at 500 and 800 GeV.

Order of magnitude improvement in limits when top spin is measured.

Effective use of beam polarization and spin-momentum correlations for new physics searches.

Abstract

We utilize top polarization in the process e+ e-\rightarrow t\bar{t} at the ILC with transverse beam polarization to probe interactions of the scalar and tensor type beyond the standard model and to disentangle their individual contributions. 90% confidence level limits on the interactions with realistic integrated luminosity are presented and are found to improve by an order of magnitude compared to the case when the spin of the top quark is not measured. Sensitivities of the order of a few times 10^{-3} TeV^{-2} for real and imaginary parts of both scalar and tensor couplings at \sqrt{s}=500 and 800 GeV with an integrated luminosity of 500 fb^{-1} and completely polarized beams is shown to be possible. A powerful model-independent framework for inclusive measurements is employed to describe the spin-momentum correlations and their C, P and T properties is presented in a technical appendix.