Linearly Polarized Photon Fusion as a Precision Probe of the Tau Lepton Dipole Moments at Lepton Colliders

TL;DR

This paper proposes a novel method using linearly polarized photon fusion and azimuthal asymmetries at future lepton colliders to precisely measure the tau lepton's dipole moments, approaching Standard Model prediction accuracy.

Contribution

It introduces new azimuthal asymmetry observables in photon-photon fusion to improve the precision of tau lepton dipole moment measurements at future colliders.

Findings

Enhanced constraints on the real part of $a_\tau$ to $[-4.6, 7.0] \times 10^{-3}$ at 2σ

Demonstrates the potential of azimuthal asymmetries for high-precision particle property measurements

Approaches the Standard Model prediction for the tau lepton's anomalous magnetic moment

Abstract

We present a comprehensive investigation into the anomalous magnetic dipole moment ($a_\tau$) and electric dipole moment ($d_\tau$) of the $\tau$ lepton using the $\gamma\gamma \to \tau^+\tau^-$ process at future lepton colliders, with the Super Tau-Charm Facility serving as a benchmark. By employing transverse-momentum-dependent factorization, we introduce novel observables derived from $\cos2\phi$, $\sin2\phi$, and $\cos4\phi$ azimuthal asymmetries to precisely probe the $\tau$ lepton's electromagnetic structure. Our analysis significantly enhances the precision of $a_\tau$ constraints within the photon-photon fusion process, yielding $\mathrm{Re}(a_\tau) \in [-4.6, 7.0] \times 10^{-3}$ at the $2\sigma$ confidence level, which approaches the precision of the Standard Model prediction. These findings highlight the considerable potential of azimuthal asymmetry measurements for high-precision determinations of fundamental particle properties at future lepton colliders.