http://arxiv.org/abs/2210.08407
We discuss production of QCD axions in a novel scenario, which assumes time-varying scale of Peccei-Quinn symmetry breaking. The latter decreases as the Universe’s temperature at early times and eventually stabilises at a large constant value. Such behavior is caused by the portal interaction between the complex field carrying Peccei-Quinn charge and a Higgs-like scalar, which is in thermal equilibrium with primordial plasma. In this scenario, axions are efficiently produced during the parametric resonance decay of the complex Peccei-Quinn field, relaxing to the minimum of its potential in the radiation-dominated stage. Notably, this process is not affected by the Universe’s expansion rate and allows to generate the required abundance of dark matter independently of an axion mass. This remains the case in the narrow parametric resonance regime corresponding to small oscillation amplitudes. Phenomenological constraints on the model parameter space strongly depend on the number density of radial field fluctuations, which are also generically excited along with axions. Even if produced with a small abundance relative to axions, radial fluctuations can have a sizeable impact on the BBN and the CMB through their decay products contributing to dark radiation. Existing constraints on dark radiation bound Peccei-Quinn symmetry breaking scale below $10^{8}-10^{9}~\mbox{GeV}$ – this paves the way for ruling out our scenario with the near future searches for axions.
S. Ramazanov and R. Samanta
Tue, 18 Oct 22
4/99
Comments: 25 pages, 3 figures
You must be logged in to post a comment.