MeV-scale reheating temperature and thermalization of the neutrino background

By M. Kawasaki, K. Kohri, N. Sugiyama. 2000

511 citations recorded by the source corpus.

The late-time entropy production by the massive particle decay induces the various cosmological effects in the early epoch and modify the standard scenario. We investigate the thermalization process of the neutrinos after the entropy production by solving the Boltzmann equations numerically. We find that if the large entropy are produced at t $\sim$ 1 sec, the neutrinos are not thermalized very well and do not have the perfect Fermi-Dirac distribution. Then the freeze-out value of the neutron to proton ratio is altered considerably and the produced light elements, especially He4, are drastically changed. Comparing with the observational light element abundances, we find that $T_R$ 2.5 MeV - 4 MeV, for the hadronic branching ratio $B_h = 10^{-2} - 1$. Possible influence of late-time entropy production on the large scale structure formation and temperature anisotropies of cosmic microwave background is studied. It is expected that the future satellite experiments (MAP and PLANCK) to measure anisotropies of cosmic microwave background radiation temperature can detect the vestige of the late-time entropy production as a modification of the effective number of the neutrino species $N_{\nu}^{\rm eff}$.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/124e69efb9842f27e4cdd1778f728a12d8b9d39b

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Citations in the corpus

Freeze-In dark matter with displaced signatures at colliders (2015, background): “It is commonly assumed that TR is very high, many orders of magnitude above the TeV scale, but observationally the most stringent constraints are from the effective number of neutrino species from CMB measurements, TR > 4 MeV [1, 2], and from Big Bang Nucleosynthesis [3, 4].”
Black hole genesis of dark matter (2017, methodology): “radiation bath at the end pBH decay { the ‘reheat’ temperature, T RH { and the yield of the DM. We will minimally impose that T RH >3MeV, the starting temperature of Big Bang Nucleosynthesis (BBN) [20, 21], and that the DM yield and mass satisfy Y = 0:43eV, ensuring, respectively, that BBN is sta”
Neutrino decoupling beyond the Standard Model: CMB constraints on the Dark Matter mass with a fast and precise Neff evaluation (2018, background): “y appeared in the literature and which explain in more detail and with explicit formulae how to perform the dierent integration steps. 3In previous versions of this paper we took the rates from Ref. [39]. However, we found that the formulae in Ref. [39] have missing factors of 2 and 8 for annihilati”