Short-range and tensor correlations in $^{4}$He and $^{8}$Be studied with the antisymmetrized quasi-cluster model

We apply the tensor version of the antisymmetrized quasi-cluster model (AQCM-T) to $^4\textrm{He}$ and $^8\textrm{Be}$ while focusing on the $NN$ correlations in $\alpha$ clusters. We adopt the $NN$ interactions including realistic ones containing a repulsive core for the central part in addition to the tensor part. In $^4\textrm{He}$, the $pn$ pair in the $^3D$ channel has been known to play a decisive role in the tensor correlation and the framework is capable of treating not only this channel but also the $NN$ correlations in the $^1S$ and $^3S$ channels. In $^8\textrm{Be}$, when two $\alpha$ clusters approach, the $^3D$ pair is suppressed because of the Pauli blocking effect, which also induces a decrease in the $^3S$ component through the $^3S$–$^3D$ coupling. These coherent effects result in the reduction of the attractive effect of the central-even interaction in the middle-range region and keep the distance between two $\alpha$ clusters.

Analyses of alpha–alpha elastic scattering data in the energy range 53.4–119.9 MeV

The differential and reaction cross sections for alpha–alpha elastic scattering at energies ranging from 50 to 120 MeV (lab. system) have been clearly explained for the first time, by using a new optical potential type. This potential, which is different from all other proposed potentials, is composed of two real parts: one is an attractive squared Woods–Saxon and the other is a repulsive core of the Woods–Saxon form in addition to a surface Woods–Saxon form for the imaginary part. The nature of the real part has been determined from available phase shifts through using inverse scattering theory for the identical particles at a fixed energy, adopting the framework of the Schrödinger equation. It is found that the repulsive real part is essential for improving the fit to the measured elastic differential cross sections, and in explaining the kink that appears at r < 1.0 fm in the shape of the real part of the potential. Using this new potential, our calculated reaction cross sections are in reasonable agreement with the ones reported by both Darriulat et al. (Phys. Rev. 137, B315 (1965). doi:10.1103/PhysRev.137.B315) and Brown and Tang (Nucl. Phys. A, 170, 225 (1971). doi:10.1016/0375-9474(71)90633-6 ).