The effects of unstable particles on light-element abundances:: Lithium versus deuterium and 3He

We reconsider the effects of the radiation from the decays of unstable particles on the production and destruction of the primordial light elements, with a view to reconciling the high primordial Li-7 abundance deduced from big bang nucleosynthesis (BBN), as implied by the baryon-to-photon ratio now inferred from the anisotropies of the cosmic microwave background (CMB), with the lower abundance of Li-7 observed in halo stars. The potential destruction of Li-7 is strongly constrained by observations of deuterium (D), He-3 and Li-6. We identify ranges for the unstable particle abundance and lifetime which would deplete Li-7 while remaining consistent with the abundance of Li-6. However, in these regions either the D abundance is unacceptably low or the ratio He-3/D is unacceptably large. We conclude that late particle decay is unable to explain both the discrepancy of the calculated Li-7 abundance and the observed Li-7 plateau. In the context of supersymmetric theories with neutralino or gravitino dark matter, we display the corresponding light-element constraints on the model parameters. (c) 2005 Elsevier B.V. All rights reserved.