https://doi.org/10.1140/epjc/s10052-025-14636-6
Regular Article - Theoretical Physics
Neutrino masses and mixing in an axion model
1
School of Natural Science, Seoul National University of Science and Technology, 01811, Seoul, Korea
2
Department of Physics, Henan Normal University, 453007, Xinxiang, China
a
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Received:
7
May
2025
Accepted:
9
August
2025
Published online:
29
August
2025
Abstract
We propose a novel framework that simultaneously addresses three critical issues: tiny neutrino masses and their mixing patterns, dark matter, and the strong CP problem. Our model extends the Peccei–Quinn (PQ) symmetry by incorporating modular 
symmetry, which plays a central role in explaining the observed neutrino mixing structure. The field content includes two vector-like colored fermions and three colored scalars as singlets, an isospin doublet inert scalar and a singlet PQ scalar, each assigned appropriate modular weights. We show that such an extension, together with a suitable assignment of modular weights to the fields, can lead to holomorphic modular forms of Yukawa interactions, which can be derived from a superpotential. Furthermore, we explore an extension of the model to include non-holomorphic Yukawa interactions in the non-supersymmetric framework and show that the results are distinct from the holomorphic case. Tiny neutrino masses are generated radiatively through colored mediators, while the KSVZ-type axion appears to dynamically resolve the strong CP problem. We investigate the phenomenology of lepton flavor violation and the muon 
anomaly within this framework. Additionally, we explore the axion’s properties and its role as dark matter.
© The Author(s) 2025
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