Light new physics and the τ lepton dipole moments

2025/11/05 by Hoferichter, Martin, Levati, Gabriele
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #Nuclear Theory (nucl-th)

paper · doi:10.48550/arxiv.2511.03786

Abstract

Testing New-Physics (NP) scenarios that couple predominantly to the third generation is notoriously difficult experimentally, as exemplified by comparing limits for the τ lepton dipole moments to those of electron and muon. In this case, extracting limits from processes such as e⁺e^-→τ⁺τ^- often relies on effective-field-theory (EFT) arguments, which allows for model-independent statements, but only applies if the NP scale is sufficiently large compared to the center-of-mass energy. In this work we offer a comprehensive analysis of light NP contributions to the τ dipole moments, providing a detailed account of the interpretation of asymmetry measurements in e⁺e^-→τ⁺τ^- that are tailored towards the extraction of dipole moments, for the test cases of new light spin-0 and spin-1 bosons. Moreover, we study the decoupling to the EFT limit in these scenarios and discuss the complementarity to constraints from other related processes, such as production in e⁺e^- reactions. While covering a wide range of light NP scenarios, as specific case study we present a detailed discussion of a tauphilic gauge vector boson at Belle II.

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