Revised Big Bang Nucleosynthesis with long-lived negatively charged massive particles: updated recombination rates, primordial 9Be nucleosynthesis, and impact of new 6Li limits

Abstract

We extensively reanalyze effects of a long-lived negatively charged massive particle, X-, on big bang nucleosynthesis (BBN). The BBN model with an X- particle was originally motivated by the discrepancy between 6,7Li abundances predicted in standard BBN model and those inferred from observations of metal-poor stars. In this model 7Be is destroyed via the recombination with an X- particle followed by radiative proton capture. We calculate precise rates for the radiative recombinations of 7Be, 7Li, 9Be, and 4He with X-. In nonresonant rates we take into account respective partial waves of scattering states and respective bound states. The finite sizes of nuclear charge distributions cause deviations in wave functions from those of point-charge nuclei. For a heavy X- mass, m_X \gtrsim 100 GeV, the d-wave --> 2P transition is most important for 7Li and 7,9Be, unlike recombination with electrons. Our new nonresonant rate of the 7Be recombination for m_X=1000 GeV is more than 6 times larger than the existing rate. Moreover, we suggest a new important reaction for 9Be production: the recombination of 7Li and X- followed by deuteron capture. We derive binding energies of X-nuclei along with reaction rates and Q-values. We then calculate BBN and find that the amount of 7Be destruction depends significantly on the charge distribution of 7Be. Finally, updated constraints on the initial abundance and the lifetime of the X- are derived in the context of revised upper limits to the primordial 6Li abundance. Parameter regions for the solution to the 7Li problem are revised, and the primordial 9Be abundances is revised.