Relaxed big bang nucleosynthesis constraints on neutrino oscillation parameters

Abstract

We study the cosmological constraints on active-sterile neutrino oscillations ν e ↔ ν s for the case when ν s is partially filled initially, i.e. 0 < δN s < 1. We provide numerical analysis of the cosmological production of 4 He, in the presence of ν e ↔ ν s oscillations, effective after neutrino decoupling, accounting for all known oscillations effects on cosmological nucleosynthesis. Cosmological constraints on oscillation parameters corresponding to higher than 5% 4 He overproduction and different non-zero initial populations of the sterile state δN s < 1 are calculated. These generalized cosmological constraints corresponding to δN s > 0 are relaxed in comparison with the δN s = 0 case and the relaxation is proportional to δN s .

Neutrino Mass from Cosmology

“…Correspondingly, distortions in the momentum spectra of neutrinos are expected which directly affect the production of 4 He at BBN when the active neutrinos are of the electron flavour (see e.g. [35], also for the case of non-zero initial ν s abundance). Instead, for much larger values of ∆m 2 oscillations are effective before neutrino decoupling, when weak interactions are frequent.…”

Neutrinos from the Early Universe and physics beyond standard models

“…The most stringent limits on sterile neutrino and on active-sterile oscillation parameters have been obtained from BBN considerations [41][42][43][44][45][46], and will be discussed in detail the next sections.…”

“…[15,41,42,[44][45][46]. The precise account of the energy spectrum distribution of oscillating neutrino allowed to extend the BBN constraints towards very small mass di erences -down to − .…”

Parameterizing the SFC Baryogenesis Model

“…2 The importance of a precise numerical account for the particle creation processes was explored further in refs. [68,69]. Different possibilities of SFC baryogenesis models were discussed.…”

“…In series of papers [69,75,76], we explored numerically SFC baryogenesis model. Here we present the results of our extended numerical analysis of the evolution of the baryon excess in SFC baryogenesis model and its dependence on the model parameters.…”