TY  - JOUR
PB  - SciPost Foundation
DO  - 10.21468/SciPostPhys.18.4.140
TI  - Two portals to GeV sterile neutrinos: Dipole versus mixing
PY  - 2025/04/28
UR  - https://scipost.org/SciPostPhys.18.4.140
JF  - SciPost Physics
JA  - SciPost Phys.
VL  - 18
IS  - 4
SP  - 140
A1  - Bertuzzo, Enrico
AU  - Frigerio, Michele
AB  - 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.
ER  -

@Article{10.21468/SciPostPhys.18.4.140,
	title={{Two portals to GeV sterile neutrinos: Dipole versus mixing}},
	author={Enrico Bertuzzo and Michele Frigerio},
	journal={SciPost Phys.},
	volume={18},
	pages={140},
	year={2025},
	publisher={SciPost},
	doi={10.21468/SciPostPhys.18.4.140},
	url={https://scipost.org/10.21468/SciPostPhys.18.4.140},
}