Be7 charge exchange between Be3+7 ion and an exotic long-lived negatively charged massive particle in big bang nucleosynthesis

The existence of an exotic long-lived negatively charged massive particle, i.e., X^-, during big bang nucleosynthesis can affect primordial light element abundances. In particular, the final abundance of Li7, mainly originating from the electron capture of Be7, has been suggested to be made smaller by the Be7 destruction via the radiative X^- capture of Be7 followed by the radiative proton capture of the bound state of Be7 and X ^- (BeX7). We suggest a new route of BeX7 formation, that is the Be7 charge exchange at the reaction of Be3+7 ion and X^-. The formation rate depends on the number fraction of the Be3+7 ion, the charge exchange cross section of Be3+7, and the probability that produced excited states BeX*7 are converted to the ground state. We estimate respective quantities affecting the BeX7 formation rate and find that this reaction pathway can be more important than the ordinary radiative recombination of Be7 and X^-. The effect of the charge exchange reaction is then shown in a latest nuclear reaction network calculation. Quantum physical model calculations for related reactions are needed to precisely estimate the efficiency of this pathway in the future.