Post-inflationary production of particle Dark Matter: non-minimal Natural and Coleman--Weinberg inflationary scenarios
We investigate the production of non-thermal fermionic dark matter particles during the reheating era following slow roll inflation, driven by inflaton $φ$ non-minimally coupled to the curvature scalar, $\mathcal{R}$. Two types of non-minimal couplings are considered: $ξφ^2\cal{R}$ for both natural (referred to as NM-N) and for Coleman-Weinberg (referred to as NM-CW) inflation, and $α\left(1+\cos(\fracφ{f_a})\right)$ only for natural inflation (referred to as NMP-N), where $α$ and $ξ$ are dimensionless parameters and $f_a$ is an energy scale. We determine benchmark values for slow roll inflationary scenarios satisfying current bounds from Cosmic Microwave Background (CMB) radiation measurement and find the mass of inflaton to be $m_ϕ\sim {\cal O}\left(10^{12}\right) \text{GeV}$ for all three inflationary scenarios and tensor-to-scalar ratio, $r\sim 0.0177$ (for NM-N), $\sim 0.0097$ (for NMP-N), and $r\sim 0.0157$ (for NM-CW) which fall inside $1-σ$ contour on scalar spectral index versus $r$ plane of Planck2018+BICEP3+KeckArray2018 joint analysis, and can be probed by future CMN~observations e.g. Simons Observatory. We then show that dark matter particles produced from the decay of inflaton can fully match the present-day cold dark matter (CDM) yield, as well as other cosmological constraints, if the coupling value between inflaton and dark matter, $y_χ$, and the dark matter mass, $m_χ$, are within the range $10^{-1}\gtrsim y_χ\gtrsim 10^{-20}$ for NM-N and NMP-N ($10^{-4}\gtrsim y_χ\gtrsim 10^{-20}$ for NM-CW) and ${\cal O}\left(\text{keV}\right)\lesssim m_χ\lesssim m_ϕ/2$ (for NM-N, NMP-N, and NM-CW). The exact range of $y_χ$ and $m_χ$ varies with different benchmark values as well as parameters of inflation, like energy scale of inflation and $r$, some of which are within reach of next-generation CMB experiments.