Big bang nucleosynthesis

Abstract

Primordial nucleosynthesis, or big bang nucleosynthesis (BBN), is one of the three evidences for the big bang model, together with the expansion of the Universe and the Cosmic Microwave Background. There is a good global agreement over a range of nine orders of magnitude between abundances of 4 He, D, 3 He and 7 Li deduced from observations, and calculated in primordial nucleosynthesis. However, there remain, a yet-unexplained, discrepancy of a factor 3, between the calculated and observed lithium primordial abundances, that has not been reduced, neither by recent nuclear physics experiments, nor by new observations. The precision in Deuterium observations in cosmological clouds has recently improved dramatically, so that nuclear cross sections involved in Deuterium BBN need to be known with similar precision. We will shortly discuss nuclear aspects related to BBN of Li and D, BBN with non-standard neutron sources, and finally, improved sensitivity studies using Monte Carlo that can be used in other site of nucleosynthesis.