Origin of Neutrino Masses

Determine the physical origin of neutrino masses of the three active neutrinos inferred from oscillation data by identifying the mechanism that generates non-zero neutrino masses.

Background

Neutrino oscillation measurements establish that at least two neutrino mass eigenstates are non-zero, implying physics beyond the minimal Standard Model. Pinning down the mechanism that generates these masses remains a central challenge in particle physics.

This paper investigates phenomenology where ultralight scalar dark matter interacts with sterile neutrinos, inducing time- and redshift-dependent effective masses for active neutrinos via mixing. While these effects can modify cosmological and laboratory observables, the fundamental question of how neutrino masses originate remains an open problem motivating such studies.

References

The origin of neutrino masses and the nature of dark matter constitute, at present, the two main open questions in our understanding of the Universe.

— Effects of Neutrino-Ultralight Dark Matter Interaction on the Cosmic Neutrino Background  (2406.01682 - Martínez-Miravé et al., 2024) in Section 1, Introduction (first paragraph), p. 1

The riddle of their mass, however, remains unsolved, though the combination of many experiments is now beginning to settle the so-called neutrino mass ordering — an important ingredient for interpreting future absolute-mass measurements [6].

— After 60 years, here comes the Sun  (2609.18799 - Cabrera et al., 16 Sep 2026) in Section “The pioneers' ambition: on hold for sixty years — so far”

Neutrino telescopes search for rare interactions caused by neutrinos, an elusive particle central to many open questions in the Standard Model of particle physics, such as the origin of their masses and the matter anti-matter asymmetry of the universe.

— Learning Efficient Representations of Neutrino Telescope Events  (2410.13148 - Yu et al., 2024) in Section 1 (Introduction), first paragraph

Nonetheless, several open questions remain, including the origin of neutrino masses, the nature of parity violation, and the existence of lepton flavor violation (LFV).

— Implications of the muon anomalous magnetic moment in a Doublet Left-Right Symmetric Model  (2603.28041 - Zeleny-Mora et al., 30 Mar 2026) in Introduction (Section 1)

The origin of neutrino mass remains one of the most compelling open problems in particle physics.

— Nested Disappearing-Track plus Displaced-Vertex Topology at the HL-LHC: A Dual Long-Lived-Particle Signature of the Scotogenic Model  (2609.28334 - Wang, 23 Sep 2026) in Section 1, Introduction