Abstract
We investigate a minimal neutrino portal dark matter (DM) model where a right-handed neutrino both generates the observed neutrino masses and mediates between the SM and the dark sector, which consists of a fermion and a boson. In contrast to earlier work, we explore regions of the parameter space where DM is produced via freeze-in instead of freeze-out motivated by the small neutrino Yukawa couplings in case of mathcal {O} left( mathrm {TeV} right) heavy neutrinos. For a non-resonant production of DM, its energy density is independent of the DM mass. Assuming a democratic coupling structure we find M_N approx 10 , mathrm {TeV}. For the resonant production of DM, we find that it can be produced via freeze-in or freeze-out even with couplings of mathcal {O} (10^{-5} ). However, the measurement of the Lyman-alpha forest rules out the feeble coupled freeze-out case completely, while the resonant freeze-in production is only viable for m_{DM} gtrsim 3 , mathring{keV}.
Highlights
Both dark matter (DM) and neutrino masses provide strong hints for beyond standard model physics (BSM)
We have investigated a minimal neutrino portal DM model
The SM is extended by three right-handed neutrinos which generate the neutrino masses via a type I seesaw mechanism and, act as mediator between the SM and DM
Summary
Both dark matter (DM) and neutrino masses provide strong hints for beyond standard model physics (BSM). Even in this case the right-handed neutrino can act as a mediator to DM since it is a SM singlet, a possibility which is referred to as neutrino portal DM (NPDM) [9,10,11,12] Within these works, the small neutrino masses are generated by the type I seesaw mechanism and DM is produced via the freeze-out mechanism. While they are uncharged under the SM gauge groups, they are charged under a dark symmetry, e.g. a dark U(1) or a Z2.2 Assuming the SM particles to be uncharged under the dark symmetry renders the lighter particle of χ and φ to be a stable DM candidate since the dark symmetry forbids couplings between SM and dark sector particles In this scenario, the resulting heavy neutrinos Ni mediate between the DM and the SM particles since the singlets νRi can couple to χand φ via a Yukawa coupling as long as the expression χφ is a singlet under all gauge groups. Whereas for MN ≤ MW , the W l N and Z ν N vertices are expected to contribute the most to DM production as long as MN mν
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
