Interference Resurrection of the $\tau$ Dipole through Quantum Tomography

TL;DR

This paper compares quantum information observables and traditional spin correlations in detecting the tau lepton's anomalous dipole moment, finding spin correlations more sensitive for probing new physics effects.

Contribution

It demonstrates that spin correlation observables outperform quantum information measures in sensitivity to SMEFT operators affecting the tau lepton.

Findings

Spin correlations improve sensitivity to new physics by up to a factor of 3.

Quantum information observables are less effective than spin correlations for interference resurrection.

Traditional spin correlations outperform quantum measures in detecting CP-violating effects.

Abstract

Helicity selection rules can suppress the leading contributions from dimension-6 operators in the Standard Model Effective Field Theory (SMEFT), reducing sensitivity to potential new physics. This paper explores how the interference contributions from the $\tau$ lepton's anomalous dipole moment are restored in different observable, in particular comparing the sensitivity to SMEFT operators of quantum information observables and more traditional spin correlations. We compute the sensitivity of various observables-including entanglement measures, Bell inequality violations, and quantum uncertainties-to new physics effects using Monte Carlo simulations. Spin correlation observables are found to outperform both the integrated cross-section and quantum information observables in sensitivity to both $CP$-conserving and -violating effects, improving the sensitivity to the scale of new physics by up to a factor of 3. Our results suggest that quantum information observables are suboptimal probes for resurrecting the interference, and more in general to disentangle the $CP$ properties of new physics