Programme

O.3 -- Oral, VCTP-50

Date: Monday, 4 August 2025

Time: 14:40 - 15:05

U(1)_N as a common source for light fermionic dark matter and radiative neutrino masses

D. T. Huong (1), A. E. Ca ́rcamo Hernandez(2), T. T. Hieu (3)

(1) Institute of Physics, VAST, 10 Dao Tan, Ba Dinh, Hanoi, Vietnam, (2) Universidad T ́ecnica Federico Santa Mar ́ıa, Casilla 110-V, Valpara ́ıso, Chile, (3) Department of Physics, Hanoi Pedagogical University 2, Phuc Yen, Vinh Phuc 15000, Vietnam

Within the framework of a U(1)_N extended Standard Model, we explore mechanisms to simultaneously generate small neutrino masses and keV-scale fermionic dark matter (DM). These include: a radiative seesaw mechanism to produce keV-scale DM candidates and a radiative inverse seesaw mechanism to generate the tiny masses of active neutrinos. The models residual Z_2 symmetry plays a dual role: it ensures DM stability by forbidding its decay and suppresses mixing between DM and active neutrinos, thereby evading stringent astrophysical and cosmological constraints. It is well-established that keV dark matter can be thermally generated during the early stages of the Universe, wherein it decouples while remaining relativistic, facilitated by U(1)_N portal interactions, but it gets overproduced thermally. To reconcile this overabundance with observational limits, we invoke late-time entropy dilution from the decay of long-lived particles, which effectively reduces the DM relic density. Crucially, the proposed parameter space accommodates both observational data of cosmic inflation and kev dark matter, offering a unified resolution to these distinct challenges in particle cosmology.

Presenter: Do Thi Huong