We study radiative plateau-like inflation \& Z$_{ BL}$-portal freeze-in fermionic dark matter (DM) in a minimal B-L extended model. The U(1)$_{ B-L}$ Higgs, responsible for heavy neutrino masses, also drives inflation in the early universe, thanks to radiative corrections from the heavy neutrinos \& the Z$_{ BL}$ gauge boson. In our benchmark choice for the U(1)$_{ B-L}$ gauge coupling $g_{ B-L}\sim10^{ -4}$, a light Z$_{ BL}$ boson can be explored by current and future lifetime frontier experiments, such as FASER and FASER 2 at the LHC, SHiP, Belle II and LHCb. For the benchmark, the Hubble scale of inflation ($\mathcal{ H}_{ inf}$) is very low ($\mathcal{ H}_{ inf} = \mathcal{ O}(100)$ eV) \& the inflaton turns out to be very light with mass of $\mathcal{ O}(1)$ eV, and consequently the decay width of inflaton is extremely small. We investigate a 2-field system with the inflaton/B-L Higgs and the Standard Model (SM) Higgs, and find that the reheating with a suffuciently high temperature occurs when the water-fall direction to the SM Higgs direction opens up in the trajectory of the scalar field evolution.
Categories: hep-ph astro-ph.CO