Speaker
Description
The aim of our research is to achieve a comprehensive understanding of the Big Bang Nucleosynthesis (BBN) process and to potentially resolve the Cosmological Lithium Problem (CLP). The CLP is a well-known issue in astrophysics, referring to the overestimation of the primordial $^7\mathrm{Li}$ abundance in standard BBN models compared to astronomical observations. One of the major challenges in addressing this problem is that many of the nuclear reaction cross sections relevant to BBN have not been measured over the full BBN energy range. Addressing this limitation requires a combination of experimental measurements and theoretical modeling to provide reliable cross sections for BBN calculations.
Our research employs both experimental and theoretical approaches to address the CLP: high-precision measurements of key nuclear reaction cross sections and the re-evaluation of nuclear reactions used in BBN calculations, including investigations of possible resonant contributions through flexible cross-section parametrizations.
In this study, we present the results of our previous experimental study and discuss a future theoretical approach.
The experimental approach focuses on measuring the cross section of the $^7\mathrm{Be}(d,p)^8\mathrm{Be}$ reaction, motivated by theoretical suggestions of its important role in the destruction of $^7\mathrm{Be}$ during BBN [1]. We produced a radioactive $^7\mathrm{Be}$ target and measured the $^7\mathrm{Be}(d,p)^8\mathrm{Be}$ reaction cross section at the tandem facility of Kobe University in Japan. The cross section at the lowest energy of $E_{\mathrm{c.m.}} = 0.12$ MeV was measured with the highest sensitivity achieved in previous measurements [2,3,4]. The measured $^7\mathrm{Be}(d,p)^8\mathrm{Be}$ cross sections indicate a modest impact on the CLP.
A future theoretical study is outlined, focusing on the exploration of potential resonant contributions in key nuclear reactions. In this approach, nuclear reaction cross sections are parametrized using an external functional form, enabling a flexible inclusion of resonant contributions within the BBN reaction network. This allows us to investigate whether such resonant effects could modify reaction rates relevant to BBN and thereby provide further insight into the CLP.
References
[1] S. Q. Hou et al., Phys. Rev. C 91, 055802 (2015).
[2] R. Kavanagh, Nucl. Phys. 18, 492--501 (1960).
[3] C. Angulo et al., ApJ 630, L105 (2005).
[4] N. Rijal et al., Phys. Rev. Lett. 122, 182701 (2019).
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