Abstract
The non-thermal dark matter (DM) production via the so-called freeze-in mechanism provides a simple alternative to the standard thermal WIMP scenario. In this work, we consider a popular U(1)B−L extension of the standard model (SM) in the context of inverse seesaw mechanism which has at least one (fermionic) FIMP DM candidate. Due to the added ℤ2 symmetry, a SM gauge singlet fermion, with mass of order keV, is stable and can be a warm DM candidate. Also, the same ℤ2 symmetry helps the lightest right-handed neutrino, with mass of order GeV, to be a stable or long-lived particle by making a corresponding Yukawa coupling very small. This provides a possibility of a two component DM scenario as well. Firstly, in the absence of a GeV DM component (i.e., without tuning its corresponding Yukawa coupling to be very small), we consider only a keV DM as a single component DM, which is produced by the freeze-in mechanism via the decay of the extra Z′ gauge boson associated to U(1)B−L and can consistently explain the DM relic density measurements. In contrast with most of the existing literature, we have found a reasonable DM production from the annihilation processes. After numerically studying the DM production, we show the dependence of the DM relic density as a function of its relevant free parameters. We use these results to obtain the parameter space regions that are compatible with the DM relic density bound. Secondly, we study a two component DM scenario and emphasize that the current DM relic density bound can be satisfied for a wide range of parameter space.
Highlights
The dark matter (DM) is very feebly interacting with the other particles, and as a result never achieves thermal equilibrium in the early universe with the cosmic soup
After explaining the keV Feebly Interacting Massive Particles (FIMPs) warm DM (WDM) as a successful single component FIMP DM scenario to satisfy the correct value of the DM relic density, we study a two component FIMP DM as another possible scenario in the present model, where in addition to the FIMP WDM S11, the lightest heavy right-handed neutrino νH1 can be a FIMP DM by tuning its corresponding Yukawa coupling to be very small [60, 61]
In this work we studied two beyond standard model (SM) problems, viz., the non-zero neutrino masses and the existence of the DM
Summary
S11 is a WDM candidate with mass in the few keV range [83,84,85]. We start with taking only the decay contribution and show in the left and right panels of figure 2 the variation of DM relic density as a function of z, for different values of the initial temperature T0 (= Msc/z0) and different values of the WDM mass MS11, respectively. In figure 6, we show the total relic density (blue dashed-dotted line) as well as the relative contributions of the two different types of WDM production processes, decay Variation of total WDM relic density (Ωh2) as a function of the gauge coupling g can be seen, where the BLSMIS points have been generated over the following ranges of its fundamental parameters: 1 ≤ MS11 ≤ 10 keV, 1 ≤ MZ ≤ 100 GeV, 10−12 ≤ g ≤ 10−8, Mh2 = 1 TeV, z0 = 0.01, and α = 0.01 rad. We discuss a two component FIMP DM possibility as a well-motivated scenario to get an extra relic density contribution from the lightest heavy RH neutrino, νH1 , as a GeV scale DM
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