Big Bang Nucleosynthesis―“Trojan Horse Method” Approaching the “Cosmological Lithium Problem”

Abstract

We determined the ⁷Be (n, p₀)⁷Li, ⁷Be (n, p₁)⁷Li* and ⁷Be (n, α)⁴He reaction cross sections by means of the Trojan Horse method which covered the big bang nucleosynthesis (BBN) energy range. The present and the previous data were analyzed by a multi-channel R-matrix fit, providing an improved error evaluation of the (n, p₀) channel and the first-ever quantification of the (n, p₁) contribution. The reaction rate summing both the present (n, p₀) and (n, p₁) contributions imposes a new constraint on the ⁷Li abundance in the BBN calculation, which offers a “free ⁷Li reduction” to further theoretical challenges to the long-standing cosmological lithium problem.