CosmicLi6andLi7problems and BBN with long-lived charged massive particles

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 lightelement 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 2 H, 6 Li, and 7 Li 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 6 Li and 7 Li problems. It is shown that a priorly suggested simultaneous solution of the 6 Li and 7 Li problems for a relic decaying at τx ≈ 1000 sec is only very weakly dependent on the relic being neutral or charged, unless its hadronic branching ratio is B h ≪ 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 6 Li and 7 Li problem for long decay times τx > ∼ 10 6 sec seems possible but fairly unlikley.

New results on catalyzed big bang nucleosynthesis with a long-lived negatively charged massive particle

“…They then found that 9 Be * (1/2 + , 1.684 MeV) X is not a resonance but a bound state located below the 8 Be X +n threshold. The resonant 8 Be X (n,X − ) 9 Be X reaction is thus not likely to contribute.…”

“…[7]). A resonant reaction 8 Be X (n,X − ) 9 Be through the atomic ground state of 9 Be * (1/2 + ,1.684 MeV) X , i.e., an atom composed of the 1/2+ nuclear excited state of 9 Be and an X − particle, has also been suggested as a possible reaction to produce mass 9 nuclides [10]. Kamimura et al [9], however, adopted a root mean square charge radius for 8 Be of 3.39 fm as a more realistic input.…”

“…Of particular interest in this work is the apparent discrepancy between the inferred primordial abundances of 6 Li and 7 Li and the predictions of standard BBN. A popular model to resolve this discrepancy is the existence of an unstable negatively charged supersymmetric particle during the nucleosynthesis epoch [1][2][3][4][5][6][7][8][9][10][11][12][13]. Depending upon their abundance and lifetime [7], such particles can catalyze the nuclear reactions leading to enhanced 6 Li [1] and depleted 7 Li [5,6] as required by observations.…”

“…They affect the nucleosynthesis in a different way [1][2][3][4][5][6][7][8][9][10][11][12][13]. The X − particles become electromagnetically bound to positively charged nuclides with binding energies of ∼ O(0.1−1) MeV with the largest binding energies for heavier nuclei with larger charges.…”

6Li/7Li estimates for metal-poor stars

“…Their derived abundances in metal-poor stars are difficult to reconcile simultaneously with standard predictions. Different production sites in the early Galaxy have been discussed: Big Bang nucleosynthesis (Wagoner et al 1967;Nollett et al 1997;Coc et al 2004;Jedamzik 2008), cosmic ray spallation and/or α-fusion (Reeves et al 1970;Vangioni-Flam et al 2000) and neutrino spallation (see e.g. Vangioni-Flam et al 1996).…”