Freeze-in Axion-like Dark Matter
Abstract
We present an interesting Higgs portal model where an axion-like particle (ALP) couples to the Standard Model sector only via the Higgs field. The ALP becomes stable due to CP invariance and turns out to be a natural candidate for freeze-in dark matter because its properties are controlled by the perturbative ALP shift symmetry. The portal coupling can be generated non-perturbatively by a hidden confining gauge sector, or radiatively by new leptons charged under the ALP shift symmetry. Such UV completions generally involve a CP violating phase, which makes the ALP unstable and decay through mixing with the Higgs boson, but can be sufficiently suppressed in a natural way by invoking additional symmetries.
Cite
@article{arxiv.1907.07383,
title = {Freeze-in Axion-like Dark Matter},
author = {Sang Hui Im and Kwang Sik Jeong},
journal= {arXiv preprint arXiv:1907.07383},
year = {2019}
}
Comments
1+14 pages; v2: updated ALP longevity bound from gamma ray observations, references added, version to appear in PLB