Speaker
Description
The inverse process of ${}^{9}\mathrm{Be}$ photo-disintegration, including both sequential and direct reactions combining two $\alpha$ and a neutron into $^9\textrm{Be}$, is a reaction of astrophysical interest, because it represents an alternative path to the ${}^{12}\mathrm{C}$ formation in a neutron-rich environment. Here we present the study of the inclusive reaction $\gamma + {}^{9}\mathrm{Be} \to \alpha + \alpha + n$, in the low-energy regime, where the cross section is calculated using the Lorentz Integral Transform method [1]. Furthermore, we calculate the $^9\textrm{Be}$ three-body binding energy via the Non-Symmetrized Hyperspherical Harmonics (NSHH) method [2].
The shallow binding of ${}^{9}\mathrm{Be}$ below the $\alpha\alpha n$ three-body threshold and the deep binding of $\alpha$ indicates a clear separation of energy scales, therefore, in the low energy regime, we are allowed to study ${}^{9}\mathrm{Be}$ as a three-body clustering system interacting through effective potentials. In the literature one finds calculations where $\alpha$-$\alpha$ and $\alpha$-$n$ potentials of phenomenological character have been used; here we present an attempt to use potentials derived from Halo Effective Field Theory (EFT) [3].
In order to quantify the contributions of the one- and higher-body nuclear currents to the reaction cross section, we compute the nuclear current matrix element using either the one-body convection current [4] or the dipole operator matrix element. The reason for this twofold calculation is that, at low energy, the latter includes the contributions of the one-body convection current as well as that of higher-body currents (Siegert theorem). We will discuss the results focusing on the interplay between these two contributions, driven by the EFT parameters, and in connection with the experimental results.
References
[1] V. D. Efros, et al., J. Phys. G: Nucl. Part. Phys. 34, R459 (2007).
[2] S. Deflorian, N. Barnea, W. Leidemann, and G. Orlandini, Few-Body Syst. 54, 1879 (2013).
[3] H. W. Hammer, C. Ji, and D. R. Phillips, J. Phys. G: Nucl. Part. Phys. 44, 103002 (2017).
[4] E. Filandri, Doctoral Thesis, Università di Trento (2022).
