Decoupling Neutrino Magnetic Moment from Mass with $SU(2)_L$ Invariance

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Hauptverfasser: Pagès, Julie, Thapa, Anil
Format: Preprint
Veröffentlicht: 2025
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author Pagès, Julie
Thapa, Anil
author_facet Pagès, Julie
Thapa, Anil
contents Standard Model extensions that yield observable neutrino magnetic moments typically also induce large neutrino masses, incompatible with experimental limits. This tension motivates the search for mechanisms that naturally decouple magnetic moments from mass generation without requiring fine-tuning. In this letter, we propose a novel mechanism for generating Dirac and Majorana neutrino magnetic moment, in which the associated mass contribution is forbidden by $SU(2)_L$ invariance. By carefully selecting the $SU(2)_L$ representations connecting the neutrino to the loop diagram, we ensure that only the effective dipole operator involving the non-Abelian part of the photon -- the neutral $SU(2)_L$ gauge boson -- is generated. Crucially, the corresponding mass diagram, obtained by removing the external gauge boson leg, vanishes. We provide explicit UV completions that implement this mechanism and yield neutrino magnetic moments within the sensitivity of current and future experiments.
format Preprint
id arxiv_https___arxiv_org_abs_2506_15777
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Decoupling Neutrino Magnetic Moment from Mass with $SU(2)_L$ Invariance
Pagès, Julie
Thapa, Anil
High Energy Physics - Phenomenology
Standard Model extensions that yield observable neutrino magnetic moments typically also induce large neutrino masses, incompatible with experimental limits. This tension motivates the search for mechanisms that naturally decouple magnetic moments from mass generation without requiring fine-tuning. In this letter, we propose a novel mechanism for generating Dirac and Majorana neutrino magnetic moment, in which the associated mass contribution is forbidden by $SU(2)_L$ invariance. By carefully selecting the $SU(2)_L$ representations connecting the neutrino to the loop diagram, we ensure that only the effective dipole operator involving the non-Abelian part of the photon -- the neutral $SU(2)_L$ gauge boson -- is generated. Crucially, the corresponding mass diagram, obtained by removing the external gauge boson leg, vanishes. We provide explicit UV completions that implement this mechanism and yield neutrino magnetic moments within the sensitivity of current and future experiments.
title Decoupling Neutrino Magnetic Moment from Mass with $SU(2)_L$ Invariance
topic High Energy Physics - Phenomenology
url https://arxiv.org/abs/2506.15777