Axionlike dark matter from the type-II seesaw mechanism

Abstract

Although axionlike particles (ALPs) are popular dark matter candidates, their mass generation mechanisms as well as cosmic thermal evolutions are unclear. In this paper, we propose a new mass generation mechanism of an ALP during the electroweak phase transition in the presence of the type-II seesaw mechanism. In this scenario, the ALP gets mass uniquely at the electroweak scale, so there is a cutoff scale on the ALP oscillation temperature that is irrelevant to the specific mass of the ALP, serving as a distinctive feature of this scenario. Interactions of the ALP have been systematically studied, which shows that the ALP does not couple to diphotons. Instead, it couples to active neutrinos as well as the electron. Therefore, it can be boosted by cosmic rays and can be tested in proposed direct detection experiments with various condensed matter materials as targets. Published by the American Physical Society 2024