The cosmic 6Li and 7Li problems and BBN with long-lived charged massive particles

TL;DR

This paper investigates how long-lived charged massive particles (CHAMPs) during Big Bang nucleosynthesis could resolve the lithium abundance discrepancies, analyzing their effects on light element synthesis with detailed reactions and decay processes.

Contribution

It provides a comprehensive numerical and analytical analysis of CHAMP effects on BBN, including previously neglected processes, and assesses their potential to solve lithium problems.

Findings

CHAMPs can significantly alter light element yields during BBN.

A simultaneous solution to Li6 and Li7 problems is weakly dependent on relic neutrality.

Long decay times for relics may allow solutions but are unlikely within current constraints.

Abstract

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.