The $\tau$ Magnetic Dipole Moment at Future Lepton Colliders

TL;DR

Future high-energy lepton colliders could significantly improve measurements of the tau lepton's magnetic dipole moment by probing rare Higgs decays, offering insights into potential new physics beyond the Standard Model.

Contribution

The paper demonstrates that future lepton colliders can enhance sensitivity to new physics affecting the tau magnetic moment through rare Higgs decay measurements.

Findings

Future colliders can improve sensitivity by a factor of 10.

Rare Higgs decays are effective probes of new physics.

Electroweak invariance links tau magnetic moment to Higgs processes.

Abstract

The magnetic moment of the $\tau$ lepton is an interesting quantity that is potentially sensitive to physics beyond the Standard Model. Electroweak gauge invariance implies that a heavy new physics contribution to it takes the form of an operator which involves the Higgs boson, implying that rare Higgs decays are able to probe the same physics as $a_\tau$. We examine the prospects for rare Higgs decays at future high energy lepton (electron or muon) colliders, and find that such a project collecting a few ab$^{-1}$ would be able to advance our understanding of this physics by roughly a factor of 10 compared to the expected reach of the high luminosity LHC.