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

Our research goal is to measure the cross-section of the ⁷Be(d, p) reaction in search of a solution/key to the cosmological ⁷Li problem (CLP). The CLP is the overestimation of primordial ⁷Li 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 ⁷Li abundance is about three times larger than the recent precise observation [1], [2]. ⁷Li nuclei were considered to be produced predominantly by the electron capture decay of ⁷Be after the termination of nucleosynthesis in the standard BBN model. We focus on the ⁷Be(d, p) reaction since it is considered one of the contributors to ⁷Be destruction in the BBN [3]. Our experiment means that we reproduce the nuclear reactions that occurred in BBN are reproduced in the modern world. We developed a method to produce ⁷Be (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 ⁷Li particles to ⁷Be particles via the ⁷Li(p, n)⁷Be reaction [5]. We produced 3.03 × 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 ⁷Be(d, p) reaction was measured at energies 0.6, 0.86, 1.0, and 1.6 MeV. The outgoing protons were measured by layered silicon telescopes at 30 and 45 degrees.

In this talk, I will talk about the experimental setup and preliminary results of this study, including the ⁷Be(d, p) cross-section and its impact on the solution of the CLP.

References:

[1] R. H. Cyburt et al., J. Cosmol. Astropart. Phys. 11, 012 (2008).

[2] Brian D. Fields et al., J. Cosmol. Astropart. Phys. 03(2020)010.

[3] S. Q. Hou et al., Phys. Rev. C 91, 055802 (2015).

[4] ”Kobe University Tandem Electrostatic Accelerator” (Accessed 4th August 2022).

[5] K. K. Sekharan et al., Nucl. Instr. Meth. 133, 253-257 (1976).

This Friday colloquium will be hybrid. Attendees can therefore participate either in-person or via Zoom. Please join via Zoom at

https://uio.zoom.us/j/69001043754?pwd=cEJpbVE5ci9PdWNtRld2TDNNcGtKdz09

Meeting ID:690 0104 3754

Passcode: PeiseStua3

Attendees will be muted during the colloquium, but will have the opportunity to ask questions at the end by clicking on the "raise hand” button (or send a request via chat).