We review important reactions in the big bang nucleosynthesis (BBN) model involving a long-lived negatively charged massive particle, X^-, which is much heavier than nucleons. This model can explain the observed ^7Li abundances of metal-poor stars, and predicts a primordial ^9Be abundance that is larger than the standard BBN prediction. In the BBN epoch, nuclei recombine with the X^- particle. Because of the heavy X^- mass, the atomic size of bound states A_X is as small as the nuclear size.

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... nonresonant recombination rates are then dominated by the d-wave → 2P transition for ^7Li and ^7,9Be. The ^7Be destruction occurs via a recombination with the X^- followed by a proton capture, and the primordial ^7Li abundance is reduced. Also, the ^9Be production occurs via the recombination of ^7Li and X^- followed by deuteron capture. The initial abundance and the lifetime of the X^- particles are constrained from a BBN reaction network calculation. We estimate that the derived parameter region for the ^7Li reduction is allowed in supersymmetric or Kaluza-Klein (KK) models. We find that either the selectron, smuon, KK electron or KK muon could be candidates for the X^- with m_X∼ O(1) TeV, while the stau and KK tau cannot.