Sterile neutrino dark matter: impact of active-neutrino opacities

Abstract

The resonant production of keV sterile-neutrino dark matter mainly takes place during the QCD epoch of the early universe. It has been argued that it could be strongly affected by the opacities (or damping rates) of active neutrinos, which receive nonperturbative QCD-contributions. We find that for lepton asymmetries n Lα /s below 10 −6 the opacities significantly affect the sterile-neutrino yield, but that for larger asymmetries, which are necessary for producing a significant fraction of the dark matter, the yield is insensitive to changes of the opacities. Thus non-perturbative QCD contributions to the opacities at temperatures around 160 MeV will not affect this dark matter scenario. We obtain larger sterile-neutrino yields than previous studies, and thus weaker lower limits on the active-sterile mixing angle from Big Bang Nucleosynthesis.

Momentum distributions of cosmic relics: Improved analysis

“…We have presented a computational method that is generally applicable for solving the coupled set of Boltzmann equations for phase space distribution functions of cosmic relics. Similar techniques have been developed earlier in the context of the neutrino astrophysics [13][14][15][16], but until now they have not been carefully adapted to be used in the dark matter abundance calculations. For earlier implementations that use different levels of approximations for the collision integrals see however [6,7].…”

“…[6] are also performed in terms of the physical momentum, which requires that the derivative term ∂ p f (p, t) is computed from the discrete data. This is a potential source of inaccuracy [7], which can be alleviated by using large number of grid points, or by judicious implementation of a dynamical grid, as was done in the context of resonant neutrino oscillations [13][14][15][16]. Anyway, this problem is completely avoided by the use of the method of characteristics in our formulation.…”

“…In this paper we complement these earlier analyses by presenting a numerical method based on discretization of the momentum space, that allows for a completely general solution of the Boltzmann equations for the momentum distributions of multiple number of particle species, any number of which can be out of equilibrium. We note that advanced momentum-dependent methods have also been developed and used to treat neutrino-oscillations in the early universe [13][14][15][16].…”

Baryogenesis from the weak scale to the grand unification scale

“…Additional constraints (not shown) come from structure formation (Schneider, 2016). From Bodeker and Klaus, 2020. masses in the range 0.1-50 GeV. 20 It is encouraging that mixings and masses with successful leptogenesis can be probed through a number of ongoing experiments.…”

Axion–Sterile Neutrino Dark Matter

“…The second mechanism to produce sterile neutrino DM is a resonantly enhanced version of the DW mechanism, which relies on a non-vanishing lepton asymmetry L [39,85] and is based on the Mikheyev-Smirnov-Wolfenstein effect [86,87] (see Refs. [88][89][90] for more recent and precise calculations). In practice, the effective mixing in the plasma is enhanced by L, such that the abundance of active neutrinos allows the creation of sterile neutrinos more efficiently.…”