BBN as Probe of Fundamental Physics

Popa, L.; Caramete, A.

doi:10.5772/34349

Cited by 1 publication

(1 citation statement)

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“…If a primordial lepton asymmetry is present in the early Universe, the active-sterile transitions could be resonantly enhanced, as proposed by Shi and Fuller (SF) [28]. This mechanism produces a relatively cold DM component in addition to the thermal DW part, which leads to a colder spectrum in accordance with all bounds [17,29,30] -however, note that also this mechanism is in some tension with data if the 3.5 keV line is taken seriously [31]. In theories with an extended gauge group, the sterile neutrinos could equilibrate and be produced via generic freeze-out, if the resulting overabundance is corrected by a sufficient amount of entropy production [32,33] -however this scenario, even though not fully excluded, is on quite general grounds threatened by big bang nucleosynthesis [34].…”

Section: Introductionmentioning

confidence: 88%

keV sterile neutrino dark matter from singlet scalar decays: basic concepts and subtle features

Merle

Totzauer

2015

J. Cosmol. Astropart. Phys.

147

244

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We perform a detailed and illustrative study of the production of keV sterile neutrino Dark Matter (DM) by decays of singlet scalars in the early Universe. In the current study we focus on providing a clear and general overview of this production mechanism. For the first time we study all regimes possible on the level of momentum distribution functions, which we obtain by solving a system of Boltzmann equations. These quantities contain the full information about the production process, which allows us to not only track the evolution of the DM generation but to also take into account all bounds related to the spectrum, such as constraints from structure formation or from avoiding too much dark radiation. In particular we show that this simple production mechanism can, depending on the regime, lead to strongly non-thermal DM spectra which may even feature more than one peak in the momentum distribution. These cases could have particularly interesting consequences for cosmological structure formation, as their analysis requires more refined tools than the simplistic estimate using the free-streaming horizon. Here we present the mechanism including all concepts and subtleties involved, for now using the assumption that the effective number of relativistic degrees of freedom is constant during DM production, which is applicable in a significant fraction of the parameter space. This allows us to derive analytical results to back up our detailed numerical computations, thus leading to the most comprehensive picture of keV sterile neutrino DM production by singlet scalar decays that exists up to now. *

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