Big-bang nucleosynthesis and hadronic decay of long-lived massive particles

Abstract

We study the big-bang nucleosynthesis (BBN) with the long-lived exotic particle, called X. If the lifetime of X is longer than ∼ 0.1 sec, its decay may cause nonthermal nuclear reactions during or after the BBN, altering the predictions of the standard BBN scenario. We pay particular attention to its hadronic decay modes and calculate the primordial abundances of the light elements. Using the result, we derive constraints on the primordial abundance of X.Compared to the previous studies, we have improved the following points in our analysis: The JETSET 7.4 Monte Carlo event generator is used to calculate the spectrum of hadrons produced by the decay of X; The evolution of the hadronic shower is studied taking account of the details of the energy-loss processes of the nuclei in the thermal bath; We have used the most recent observational constraints on the primordial abundances of the light elements; In order to estimate the uncertainties, we have performed the Monte Carlo simulation which includes the experimental errors of the cross sections and transfered energies.We will see that the non-thermal productions of D, 3 He, 4 He and 6 Li provide stringent upper bounds on the primordial abundance of late-decaying particle, in particular when the hadronic branching ratio of X is sizable. We apply our results to the gravitino problem, and obtain upper bound on the reheating temperature after inflation.

Gravitino dark matter and cosmological constraints

“…[29,31]. We have applied the BBN bounds from the observed abundances of primordial D and 4 He since they are the most reliable ones.…”

“…For 10 7 s τ NLSP 10 12 s, the reprocessing of light elements through energetic electromagnetic showers, i.e., photo-dissociation, can become more significant than hadro-dissociation. (For details, see [32,29] and references therein.) The constraints on electromagnetic and hadronic energy release can be quantified conveniently in terms of upper bounds on the quantities…”

“…[28,29]. These constraints were extracted with the following observational values of the light element abundances (1σ error):…”

“…9. For more details on these limits and their interpretation, we refer to the original papers [29,31].…”

Quintessential kination and thermal production of gravitinos and axinos

“…The latter requirement has to be satisfied also for unstable G. This restriction imposes a tight upper bound on the initial ("reheating") temperature, T I , of the universe in the SC [22,23,33,34,35]. On the other hand, if one of the e-WIMPs is a stable LSP, it has to obey the CDM constraint.…”