New constraints on radiative decay of long-lived particles in big bang nucleosynthesis with new 4He photodisintegration data

A recent measurement of He-4 photodisintegration reactions, He-4(gamma, p)H-3 and He-4(gamma, n)He-3 with laser-Compton photons shows smaller cross sections than those estimated by other previous experiments at E-gamma less than or similar to 30 MeV. We study big bang nucleosynthesis with the radiative particle decay using the new photodisintegration cross sections of He-4 as well as previous data. The sensitivity of the yields of all light elements D, T, He-3, He-4, Li-6, Li-7, and Be-7 to the cross sections is investigated. The change of the cross sections has an influence on the nonthermal yields of D, He-3, and He-4. On the other hand, the nonthermal Li-6 production is not sensitive to the change of the cross sections at this low energy, since the nonthermal secondary synthesis of Li-6 needs energetic photons of E-gamma greater than or similar to 50 MeV. The nonthermal nucleosynthesis triggered by the radiative particle decay is one of candidates of the production mechanism of Li-6 observed in metal-poor halo stars. In the parameter region of the radiative particle lifetime and the emitted photon energy, which satisfies the Li-6 production above the abundance level observed in metal-poor halo stars, the change of the photodisintegration cross sections at E-gamma less than or similar to 30 MeV as measured in the recent experiment leads to similar to 10% reduction of resulting He-3 abundance, whereas the Li-6 abundance does not change for this change of the cross sections of He-4(gamma, p)H-3 and He-4(gamma, n)He-3. The Li-6 abundance, however, could show a sizable change and therefore the future precise measurement of the cross sections at high energy E-gamma greater than or similar to 50 MeV is highly required.