Speaker
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).
