Abstract
We study effects of long-lived massive particles, which decay during the big-bang nucleosynthesis (BBN) epoch, on the primordial abundances of light elements. Compared to the previous studies, (i) the reaction rates of the standard BBN reactions are updated, (ii) the most recent observational data of light element abundances and cosmological parameters are used, (iii) the effects of the interconversion of energetic nucleons at the time of inelastic scatterings with background nuclei are considered, and (iv) the effects of the hadronic shower induced by energetic high energy anti-nucleons are included. We compare the theoretical predictions on the primordial abundances of light elements with latest observational constraints, and derive upper bounds on relic abundance of the decaying particle as a function of its lifetime. We also apply our analysis to unstable gravitino, the superpartner of the graviton in supersymmetric theories, and obtain constraints on the reheating temperature after inflation.
Highlights
Big-bang nucleosynthesis (BBN) is one of the most important predictions of big-bang cosmology
We study the effects of long-lived massive particles, which decayed during the big-bang nucleosynthesis (BBN) epoch, on the primordial abundance of light elements
Compared to previous studies, (i) the reaction rates of standard BBN reactions are updated, (ii) the most recent observational data on the light element abundance and cosmological parameters are used, (iii) the effects of the interconversion of energetic nucleons at the time of inelastic scattering with background nuclei are considered, and (iv) the effects of the hadronic shower induced by energetic high-energy antinucleons are included
Summary
Big-bang nucleosynthesis (BBN) is one of the most important predictions of big-bang cosmology. In order not to spoil the agreement between theoretical predictions and observational constraints, upper bounds on the primordial abundance of the unstable particles are obtained. Such constraints have been intensively studied in the past. The purpose of this paper is to revisit the BBN constraints on long-lived particles, which we call X, taking into account recent progress in theoretical and observational studies of the primordial abundance of the light elements.
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