Relic neutrinos: Antineutrinos of primordial nucleosynthesis

Abstract

For the first time the antineutrino spectrum formed as a result of neutron and tritium decays during the epoch of primordial nucleosynthesis is calculated. This spectrum is a non-thermal increase in addition to the standard cosmic neutrino background (CνB) whose thermal spectrum was formed before the beginning of primordial nucleosynthesis. For energy larger than 10 −2 eV the calculated non-thermal antineutrino flux exceeds the CνB spectrum and there are no other comparable sources of antineutrino in this range. The observations of these antineutrinos will allow us to look directly at the very early Universe and non-equilibrium processes taken place before, during, and some time after primordial nucleosynthesis.

Grand Unified Neutrino Spectrum at Earth: Sources and Spectral Components

“…4 are β unstable and thus produce a small cosmic ν e or ν e density which is much smaller than the CNB density given in Eq. ( 8), but shows up at larger energies because of less redshifting due to late decays [84,85]. Ignoring for now the question of neutrino masses and flavor conversion, the resulting present-day number densities are shown in Fig.…”

“…2 of Ref. [85], where pre-asymptotic tritium was also included, producing the low-energy step-like feature. The isotropic flux shown in Ref.…”

“…The isotropic flux shown in Ref. [85] was multiplied with a factor 2/c to obtain our number density. 3 Our integrated ν e density then corresponds well to the tritium density in Eq.…”

Cosmic neutrino background search experiments as decaying dark matter detectors

“…We also show the results of the recent computations of the low energy thermal component of solar neutrinos [21] and the antineutrino flux from the decay of neutrons and tritons produced in primordial nucleosynthesis [22], which extend into the 0.1-1 eV range but in relatively low numbers.…”

“…1. The flux of neutrinos from J → νν, averaged over the universe, along with CνB, solar ν [19,21], and atmospheric ν [20] neutrinos, as well as antineutrinos from the decay of neutrons and tritons produced in primordial nucleosynthesis [22]. We show the flux for mJ = 50 keV, τJ = 10 3 yr, and, since the decays take place before recombination, ΩJ such that this gives ∆N eff = 0.28 (solid, cyan).…”