Probing scalar particle and unparticle couplings in e+ e- -> t tbar with transversely polarized beams

TL;DR

This paper investigates how transversely polarized beams at e+ e- colliders can enhance the detection of new scalar and unparticle physics effects in top quark pair production, providing analytical tools for future experiments.

Contribution

It introduces a general formalism using spin density matrices to analytically describe the process including anomalous couplings with polarized beams.

Findings

Transversely polarized beams enable first-order sensitivity to anomalous couplings.

Analytical expressions for squared amplitudes including anomalous effects are derived.

Differences in SM and anomalous contributions can be exploited to detect new physics.

Abstract

In searching for indications of new physics scalar particle and unparticle couplings in e^+ e^- \to t\bar t, we consider the role of transversely polarized initial beams at e^+ e^- colliders. By using a general relativistic spin density matrix formalism for describing the particles spin states, we find analytical expressions for the squared amplitude of the process with t or \bar t polarization measured, including the anomalous coupling contributions. Thanks to the transversely polarized initial beams these contributions are first order anomalous coupling corrections to the Standard Model (SM) contributions. We present and analyse the main features of the SM and anomalous coupling contributions. We show how differences between SM and anomalous coupling contributions provide means to search for anomalous coupling manifestations at future e^+ e^- linear colliders.