Review on effects of long-lived negatively charged massive particles on Big Bang Nucleosynthesis

Abstract

We review important reactions in the Big Bang Nucleosynthesis (BBN) model involving a long-lived negatively charged massive particle, [Formula: see text], 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 [Formula: see text] particle. Because of the heavy [Formula: see text] mass, the atomic size of bound states [Formula: see text] is as small as the nuclear size. The nonresonant recombination rates are then dominated by the [Formula: see text]-wave [Formula: see text] transition for 7Li and [Formula: see text]Be. The 7Be destruction occurs via a recombination with the [Formula: see text] followed by a proton capture, and the primordial 7Li abundance is reduced. Also, the 9Be production occurs via the recombination of 7Li and [Formula: see text] followed by deuteron capture. The initial abundance and the lifetime of the [Formula: see text] particles are constrained from a BBN reaction network calculation. We derived parameter region for the 7Li reduction 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 [Formula: see text] with [Formula: see text] TeV, while the stau and KK tau cannot.