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

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