New Constraints on Radiative Decay of Long-Lived Particles in Big Bang Nucleosynthesis with New 4He Photodisintegration Data
Abstract
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 Eγ 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 non-thermal yields of D, 3He and 4He. On the other hand, the non-thermal 6Li production is not sensitive to the change of the cross sections at this low energy, since the non-thermal secondary synthesis of 6Li needs energetic photons of Eγ 50 MeV. The non-thermal nucleosynthesis triggered by the radiative particle decay is one of candidates of the production mechanism of 6Li observed in metal-poor halo stars (MPHSs). 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 MPHSs, the change of the photodisintegration cross sections at Eγ 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 Eγ 50 MeV is highly required.