The cosmic 6Li and 7Li problems and BBN with long-lived charged massive particles
Résumé
Charged massive particles (CHAMPs), when present during the Big Bang nucleosynthesis (BBN) era, may significantly alter the synthesis of light elements when compared to a standard BBN scenario. This is due to the formation of bound states with nuclei. This paper presents a detailed numerical and analytical analysis of such CHAMP BBN. All reactions important for predicting light-element yields are calculated within the Born approximation. Three priorly neglected effects are treated in detail:(a) photodestruction of bound states due to electromagnetic cascades induced by the CHAMP decay, (b) late-time efficient destruction/production of H2, Li6, and Li7 due to reactions on charge Z=1 nuclei bound to CHAMPs, and (c) CHAMP exchange between nuclei. Each of these effects may induce orders-of-magnitude changes in the final abundance yields. The study focusses on the impact of CHAMPs on a possible simultaneous solution of the Li6 and Li7 problems. It is shown that a priorly suggested simultaneous solution of the Li6 and Li7 problems for a relic decaying at tau_x = 1000 sec is only very weakly dependent on the relic being neutral or charged, unless its hadronic branching ratio is Bh << 10^-4 very small. By use of a Monte-Carlo analysis it is shown that within CHAMP BBN the existence of further parameter space for a simultaneous solution of the Li6 and Li7 problem for long decay times tau_x > 10^6 sec seems possible but fairly unlikely.