Bounds on long-lived charged massive particles from Big Bang nucleosynthesis

Abstract

The Big Bang nucleosynthesis (BBN) process in the presence of charged massive particles(CHAMPs) is studied in detail. All currently known effects due to the existence of boundstates between CHAMPs and nuclei, including possible late-time destruction of6Li and 7Li, are included. The study sets conservative bounds on CHAMP abundances in the decaytime range . It is stressed that the production of6Li at early timesT∼10 keV is overestimatedby a factor ∼10 when the approximation of the Saha equation for the4He boundstate fraction is utilized. To obtain conservative limits on the abundance of CHAMPs, a Monte Carlo analysiswith ∼3 × 106 independent BBN runs, varying the reaction rates of 19 different reactions, is performed.The analysis yields the surprising result that, except for small areas in the particleparameter space, conservative constraints on the abundance of decaying charged particlesare currently very close to those of neutral particles. It is shown that, in the case that therates of a number of heretofore unconsidered reactions may be determined reliably in thefuture, it is conceivable that the limit on CHAMPs in the early Universe could be tightenedby orders of magnitude.