Post-inflationary production of particle Dark Matter: Hilltop and Coleman-Weinberg inflation

Abstract

We investigate the production of non-thermal dark matter (DM), $\chi$, during post-inflationary reheating era. For inflation, we consider two slow roll single field inflationary scenarios - generalized version of Hilltop (GH) inflation, and Coleman-Weinberg (CW) inflation. Using a set of benchmark values that comply with the current constraints from Cosmic Microwave Background Radiation (CMBR) data for each inflationary model, we explored the parameter space involving mass of dark matter particles, $m_\chi$, and coupling between inflaton and $\chi$, $y_\chi$. For these benchmarks, we find that tensor-to-scalar ratio $r$ can be as small as $2.69\times 10^{-6}$ for GH and $1.91\times 10^{-3}$ for CW inflation, both well inside $1-\sigma$ contour on scalar spectral index versus $r$ plane from Planck2018+BICEP3+KeckArray2018 dataset, and testable by future cosmic microwave background (CMB) observations e.g. Simons Observatory. For the production of $\chi$ from the inflaton decay satisfying CMB and other cosmological bounds and successfully explaining total cold dark matter density of the present universe, we find that $y_\chi$ should be within this range ${\cal O}\left(10^{-4}\right) \gtrsim y_\chi\gtrsim {\cal O}\left(10^{-20}\right)$ for both inflationary scenarios. We also show that, even for the same inflationary scenario, the allowed parameter space on reheating temperature versus $m_\chi$ plane alters with inflationary parameters including scalar spectral index, $r$, and energy scale of inflation.