Constraints on Ωb from nucleosynthesis of 7Li in the standard big bang model -: art. no. 043510

We update standard big bang nucleosynthesis (SBBN) calculations on the basis of recent nuclear physics compilations (NACRE in particular), experimental and theoretical works. By a Monte Carlo technique, we calculate the uncertainties on the light element yields (He-4, D, He-3 and Li-7) related to nuclear reactions. The results are compared to observations that are thought to be representative of the corresponding primordial abundances. It is found that Li-7 could lead to more stringent constraints on the baryonic density of the universe (Omega(b)h(2)) than deuterium, because of much higher observation statistics and an easier extrapolation to primordial values. The confrontation of SBBN results with Li-7 observations is of special interest since other independent approaches have also recently provided Omega(b)h(2) Values: (i) the anisotropies of the cosmic microwave background by the BOOMERANG, CBI, DASI and MAXIMA experiments and (ii) the Lyman-alpha forest at high redshift. A comparison between these results obtained by different methods provides a test of their consistency and could provide a better determination of the baryonic density in the universe. However, the agreement between Omega(b)h(2) values deduced from SBBN calculation and Li-7 observation on the one hand and CMB observations on the other hand is only marginal.