Four-nucleon scattering with a correlated Gaussian basis method

TL;DR

This paper develops a correlated Gaussian basis method to study four-nucleon scattering, highlighting the impact of tensor forces and cluster distortions using realistic and effective interactions.

Contribution

It introduces a new triple global vector representation for correlated Gaussian basis functions in four-body nuclear scattering calculations.

Findings

Realistic interactions show strong channel coupling in phase shifts.

Tensor forces significantly affect cluster distortions and energy splittings.

Effective interactions fail to reproduce certain experimental splittings.

Abstract

Elastic-scattering phase shifts for four-nucleon systems are studied in an $ab$-$initio$ type cluster model in order to clarify the role of the tensor force and to investigate cluster distortions in low energy $d+d$ and $t+p$ scattering. In the present method, the description of the cluster wave function is extended from a simple (0$s$) harmonic-oscillator shell model to a few-body model with a realistic interaction, in which the wave function of the subsystems are determined with the Stochastic Variational Method. In order to calculate the matrix elements of the four-body system, we have developed a Triple Global Vector Representation method for the correlated Gaussian basis functions. To compare effects of the cluster distortion with realistic and effective interactions, we employ the AV8$^{\prime}$ potential as a realistic interaction and the Minnesota potential as an effective interaction. Especially for $^1S_0$, the calculated phase shifts show that the $t+p$ and $h+n$ channels are strongly coupled to the $d+d$ channel for the case of the realistic interaction. On the contrary, the coupling of these channels plays a relatively minor role for the case of the effective interaction. This difference between both potentials originates from the tensor term in the realistic interaction. Furthermore, the tensor interaction makes the energy splitting of the negative parity states of $^4$He consistent with experiments. No such splitting is however reproduced with the effective interaction.