Current and future constraints on heavy New Physics from $\tau$ weak dipole moments

Košnik, Nejc (author), Polonsky, Zachary (author), Smolkovič, Aleks (author)

We study the weak magnetic and electric dipole moments of the $\tau$ lepton as precision tests of the Standard Model (SM) and probes of heavy New Physics (NP). We present an updated SM prediction for the $\tau$ 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 $\tau$ dipole operators from a combination of observables: the $\tau$ 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 $\tau$ 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 $\tau$ weak dipole moments are already among the leading probes of the $\tau$ dipole operators, and will become increasingly dominant at future colliders.

• Language: English
• Keywords: electroweak precision physics, higher order electroweak calculations, electric dipole moments, Standard Model Effective Field Theory
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 31 str.
• Numbering: Vol. 2026, art. no. 129
• PID: 20.500.12556/RUL-187933
• UDC: 539.120
• ISSN on article: 1029-8479
• DOI: 10.1007/JHEP09(2026)129
• COBISS.SI-ID: 291277315
• Publication date in RUL: 16.09.2026

Record is a part of a journal

• Title: The journal of high energy physics
• Shortened title: J. high energy phys.
• Publisher: SISSA
• ISSN: 1029-8479
• COBISS.SI-ID: 1314148

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: fizika visokih energij, Standardni model, Nova fizika