Current and future constraints on heavy New Physics from τ weak dipole moments
Abstract
We study the weak magnetic and electric dipole moments of the τ lepton as precision tests of the Standard Model (SM) and probes of heavy New Physics (NP). We present an updated SM prediction for the τ weak magnetic dipole moment at one loop, including a careful assessment of theoretical uncertainties from electroweak scheme dependence. Working within the SM Effective Field Theory, we derive comprehensive current constraints on the τ dipole operators from a combination of observables: the τ weak and electromagnetic dipole moments, high-mass Drell-Yan tails at the LHC, Z partial decay widths, and the electron electric dipole moment. Finally, we assess the prospects of measuring the SM value of the τ weak magnetic moment at the FCC-ee Tera-Z run, and project the sensitivities of the leading observables to heavy NP at FCC-ee and HL-LHC, incorporating informed assumptions about improvements of systematic uncertainties. We find that the τ weak dipole moments are already among the leading probes of the τ dipole operators, and will become increasingly dominant at future colliders.
Versions
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BibTeX
@misc{kosnik2026current,
title = {{Current and future constraints on heavy New Physics from $τ$ weak dipole moments}},
author = {Nejc Košnik and Zachary Polonsky and Aleks Smolkovič},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.07232},
eprint = {2606.07232},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.07232},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Current and future constraints on heavy New Physics from τ weak dipole moments
AU - Nejc Košnik
AU - Zachary Polonsky
AU - Aleks Smolkovič
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2606.07232
UR - https://arxiv.org/abs/2606.07232
AB - We study the weak magnetic and electric dipole moments of the τ lepton as precision tests of the Standard Model (SM) and probes of heavy New Physics (NP). We present an updated SM prediction for the τ weak magnetic dipole moment at one loop, including a careful assessment of theoretical uncertainties from electroweak scheme dependence. Working within the SM Effective Field Theory, we derive comprehensive current constraints on the τ dipole operators from a combination of observables: the τ weak and electromagnetic dipole moments, high-mass Drell-Yan tails at the LHC, Z partial decay widths, and the electron electric dipole moment. Finally, we assess the prospects of measuring the SM value of the τ weak magnetic moment at the FCC-ee Tera-Z run, and project the sensitivities of the leading observables to heavy NP at FCC-ee and HL-LHC, incorporating informed assumptions about improvements of systematic uncertainties. We find that the τ weak dipole moments are already among the leading probes of the τ dipole operators, and will become increasingly dominant at future colliders.
ER -