A3F-CNS Summer School 2022

Study of the contribution of the 7Be(d, p) reaction to the 7Li problem in the Big-Bang Nucleosynthesis

20 Aug 2022, 13:45

15m

Shinrin-Koen Heitage Resort

Experimental Nuclear Physics Young Scientist Session 1

Speaker

Azusa Inoue (Research Center for Nuclear Physics, Osaka university)

Description

Our research goal is to measure the cross-section of the ${}^7$Be($d$, $p$) reaction in search of a solution to the cosmological ${}^7$Li problem (CLP). The CLP is the overestimation of primordial ${}^7$Li abundance in the standard Big-Bang nucleosynthesis (BBN) model compared to observed abundances, a major unresolved problem in modern astrophysics. A recent theoretical BBN model emphasized the primordial ${}^7$Li abundance is about three times larger than the recent precise observation [1], [2]. ${}^7$Li nuclei were considered to be produced predominantly by the electron capture decay of ${}^7$Be after the termination of nucleosynthesis in the standard BBN model. We focus on the ${}^7$Be($d$, $p$) reaction since it is considered one of the contributors to ${}^7$Be destruction in the BBN [3]. We developed a method to produce ${}^7$Be (half life = 53.22 days) target to measure the reaction cross-section in normal kinematics. The experiment was performed at the Tandem Electrostatic Accelerator, Kobe University [4]. A 2.36 MeV proton beam irradiated a natural-Li target to transmute ${}^7$Li particles to ${}^7$Be particles via the ${}^7$Li($p$, $n$)${}^7$Be reaction [5]. We produced 3.03$\times$10${}^{13}$ ${}^7$Be particles in the target after two days of proton irradiation. After the target production, the beam ion was changed to deuterons and the ${}^7$Be($d$, $p$) reaction measured at energies 0.6, 1.0, and 1.6 MeV. The outgoing protons were measured by layered-silicon telescopes placed at 30 and 45 degrees. In this talk, I will report the experimental setup and preliminary results of this study, including the ${}^7$Be($d$, $p$) cross-section.\
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References\par
[1] R. H. Cyburt {\it et al.}, J. Cosmol. Astropart. Phys. {\bf 11}, 012 (2008).\par
[2] Brian D. Fields {\it et al.}, J. Cosmol. Astropart. Phys. 03(2020)010.\par
[3] S. Q. Hou {\it et al.}, Phys. Rev. C {\bf 91}, 055802 (2015).\par
[4] "Kobe University Tandem Electrostatic Accelerator" \url {https://www.maritime.kobe-u.ac.jp/en/study/tandem_e.html} (Accessed 4th August 2022)\par
[5] K. K. Sekharan et al., Nucl. Instr. Meth. {\bf 133}, 253-257 (1976).