REVISED BIG BANG NUCLEOSYNTHESIS WITH LONG-LIVED, NEGATIVELY CHARGED MASSIVE PARTICLES: UPDATED RECOMBINATION RATES, PRIMORDIAL Be-9 NUCLEOSYNTHESIS, AND IMPACT OF NEW Li-6 LIMITS

초록

We extensively reanalyze the 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 the Li-6,Li-7 abundances predicted in the standard BBN model and those inferred from observations of metal-poor stars. In this model, Be-7 is destroyed via the recombination with an X- particle followed by radiative proton capture. We calculate precise rates for the radiative recombinations of Be-7, Li-7, Be-9, and He-4 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) greater than or similar to 100 GeV, the d-wave -> 2P transition is most important for Li-7 and Be-7,Be-9, unlike recombination with electrons. Our new nonresonant rate of the Be-7 recombination for m(X) = 1000 GeV is more than six times larger than the existing rate. Moreover, we suggest a new important reaction for Be-9 production: the recombination of Li-7 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 Be-7 destruction depends significantly on the charge distribution of Be-7. 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 Li-6 abundance. Parameter regions for the solution to the Li-7 problem and the primordial Be-9 abundances are revised.

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