Quantum tops at circular lepton colliders

TL;DR

This paper investigates the quantum properties of top quark pairs at lepton colliders, analyzing spin correlations, entanglement, and Bell inequality violations within the Standard Model and SMEFT, revealing rich phenomenology and potential for new physics detection.

Contribution

It provides analytical results on quantum correlations of top quarks in lepton colliders, exploring their implications for understanding the Standard Model and beyond.

Findings

Quantum observables show rich phenomenology in the SM.

Entanglement correlates with parity symmetry.

Quantum measurements can help detect new physics.

Abstract

We study the quantum properties of top quark pairs in lepton colliders with unpolarised beams, including spin correlations, entanglement, and violation of Bell inequalities. We present analytical results in the SM and in the SMEFT and discuss several practical aspects, like the choice of quantization axes and $t \bar t$ threshold effects. We also note a correspondence between parity symmetry and entanglement. We find that quantum observables exhibit a rich phenomenology in the SM, and can also provide additional leverage in detecting new physics residing at higher scales.