Intrinsic Mass Operator for Neutrinos: A Comprehensive and Conceptually Rich UV-Complete Framework

Neutrino physics continues to present one of the most intriguing windows into phenomena beyond the Standard Model. Observed neutrino oscillations imply that neutrinos possess mass, yet their origin remains elusive, particularly in light of the absence of right-handed neutrinos in the Standard Model. In this work, we propose a novel approach in which neutrino mass is derived from an intrinsic mass operator that exists independently of the Higgs mechanism. By embedding neutrino flavor states into an extended Hilbert space with internal degrees of freedom, we elevate mass to the status of a quantum operator, allowing for a natural quantization and discrete spectrum. We construct a UV-complete model involving heavy singlet neutrinos and an internal scalar field, develop the effective low-energy mass matrix, and analyze its eigenvalues and eigenvectors. Our results demonstrate that this framework reproduces the observed mass splittings, effective electron-neutrino masses, and satisfies constraints from cosmology and neutrinoless double-beta decay. Beyond numerical agreement, this formalism provides deep conceptual insight into the origin of neutrino mass and flavor oscillations.