Two portals to GeV sterile neutrinos: Dipole versus mixing
Enrico Bertuzzo, Michele Frigerio
SciPost Phys. 18, 140 (2025) · published 28 April 2025
- doi: 10.21468/SciPostPhys.18.4.140
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Abstract
Massive sterile neutrinos, also known as heavy neutral leptons, can have a mixing with active neutrinos, $\theta$, as well as a dipole coupling to the photon, $d$. We study the interplay between these two portals, considering the production from meson decays of sterile neutrinos with mass $0.1$ GeV $≲ M_N ≲ 10$ GeV, at beam-dump facilities such as NA62 and SHiP, and at the FASER2 experiment. These sterile neutrinos can be long-lived and decay into a photon in a distant detector, via the dipole operator. We find that all these experiments will be sensitive to values of $d$ which are presently unconstrained. The experimental reach varies strongly with the mass $M_N$ and the mixing $\theta$, and one observes specific correlations with the flavour of active neutrinos. The SHiP experiment will mark a jump in sensitivity: (i) it will probe a sterile dipole as small as $d\sim 10^{-8}\ \text{GeV}^{-1}$, thus testing new physics well above the electroweak scale; (ii) it may detect the active-sterile dipole to the level predicted by electroweak loops, if $\theta$ is close to the present bound.
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Authors / Affiliations: mappings to Contributors and Organizations
See all Organizations.- 1 2 Enrico Bertuzzo,
- 3 4 5 Michele Frigerio
- 1 INFN Sezione di Bologna / INFN Bologna [INFN Bologna]
- 2 Università degli Studi di Modena e Reggio Emilia / University of Modena and Reggio Emilia
- 3 Centre National de la Recherche Scientifique / French National Centre for Scientific Research [CNRS]
- 4 Université de Montpellier / University of Montpellier [UM]
- 5 Laboratoire Charles Coulomb [L2C]
- HORIZON EUROPE Marie Sklodowska-Curie Actions
- Instituto Nazionale di Fisica Nucleare (INFN) (through Organization: Istituto Nazionale di Fisica Nucleare / National Institute for Nuclear Physics [INFN])