Radiative decay of a massive particle and the nonthermal process in primordial nucleosynthesis - art. no. 103502

We consider the effects on big bang nucleosynthesis (BBN) of the radiative decay of a long-lived massive particle. If high-energy photons are emitted after the BBN epoch (t similar to1-10(3) sec), they may change the abundanc e of the light elements through photodissociation processes, which may resu lt in a significant discrepancy between standard BBN and observation. Takin g into account recent observational and theoretical developments in this fi eld, we revise our previous study constraining the abundance of the radiati vely decaying particles. In particular, on the theoretical side it was rece ntly claimed that the nonthermal production of Li-6, which is caused by the photodissociation of He-4, most severely constrains the abundance of the r adiatively decaying particle. We will see however, that it is premature to emphasize the importance of the nonthermal production of Li-6 because (i) t he theoretical computation of the Li-6 abundance has a large uncertainty du e to the lack of a precise understanding of the Li-6 production cross secti on, and (ii) the observational data of the Li-6 abundance has large errors.