New results in primordial nucleosynthesis

Big Bang Nucleosynthesis (BBN) is one of the most powerful tools to study fundamental interactions since light nuclei abundances crucially depend on many elementary particle properties, like the number of effective neutrino degrees of freedom, Nν . At the moment, however, recent data on Hemass fraction, Y4, and Deuterium (D) and Li abundances, Y2 ≡ D/H and Y7 ≡ 7 Li/H , produced during BBN are controversial, since there are different sets of results, two of them mutually incompatible: Y (l) 4 = 0.234± 0.002± 0.005 and Y (h) 4 = 0.243 ± 0.003 [1], Y (l) 2 = (3.4 ± 0.3)10 and Y (h) 2 = (1.9 ± 0.4)10 −4 [2], Y (l) 7 = (1.6 ± 0.36)10 and Y (h) 7 = (1.73± 0.21)10 −10 [3] (for a brief summary of the experimental situation on primordial abundances see Ref. [4]). In spite of this discrepancies, which could be of systematic origin, the above results for He data indicate that one is reaching a precision of the order of percent, requiring a similar level for the uncertainties on the theoretical predictions. Besides the corrections to the proton/neutron conversion rates, which fix at the freeze out temperature ∼ 1 MeV the neutron to proton density ratio, the other main source of theoretical uncertainty comes from nuclear rates relevant for nuclei