Primordial nucleosynthesis with decaying particles. I - Entropy-producing decays. II - Inert decays

The authors investigate the effect of a nonrelativistic particle X, which decays out of equilibrium, on primordial nucleosynthesis, including both the energy density of the X particle and the electromagnetic entropy production from its decay. The results are parameterized in terms of the X particle lifetime τ and the density parameter rmx, where mx is the X particle mass, and r is the ratio of X number density to photon number density prior to nucleosynthesis. The results of primordial nucleosynthesis are given for 10⁻²s ≤ τ ≤ 10⁷s, 10⁻²MeV ≤ rmx ≤ 10⁸MeV, and 10-10.5 ≤ ηf ≤ 10-7.5, where ηf is the final baryon-photon ratio.