Experimental Approach to the Key, Li Problem in the Big Bang Nucleosynthesis

2017 Fiscal Year Final Research Report

• Project/Area Number: 26287058
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Kubono Shigeru 国立研究開発法人理化学研究所, 仁科加速器研究センター, 客員主管研究員 (20126048)
• Co-Investigator(Kenkyū-buntansha): 岩佐 直仁 東北大学, 理学研究科, 准教授 (50322996) ; 川畑 貴裕 京都大学, 理学研究科, 准教授 (80359645) ; 西村 俊二 国立研究開発法人理化学研究所, その他, 研究員 (90272137)
• Project Period (FY): 2014-04-01 – 2018-03-31
• Keywords: 始原的７Ｌｉ問題 / ビッグバン元素合成 / 不安定核の核反応 / ビッグバン模型 / 宇宙核物理実験

Outline of Final Research Achievements

The primordial nucleosynthesis (BBN) is one of the key evidences that support the big bang model. However, the 7Li abundance has been over predicted by BBN simulation roughly by a factor of three, which is called the cosmological Li problem. We have studied the nuclear physics side for this problem by experiments. Namely, we have experimmentally studied for the first time the cross sections of (1) the 7Be(n.a)4He and (2) the 7Be(n,p1)7Li*(1/2) reaction at the BBN temperature region, and succeeded deriving them.
The reaction rate of (1) was found to be smaller by a factor of ten than the postulated value currently adopted, and thus we have identified that the reaction of (1) has a negligible influence to the Li problem.
The cross section of (2) has been neglected up to now, but our experimental result indicates that this channel contributes signifcantly to the destruction of 7Be. Thus, the reaction of (2) has been concluded to be included in the BBN simulation.

Free Research Field

原子核物理実験