High-momentum components in the $^4$He nucleus caused by inter-nucleon correlations

TL;DR

This paper investigates the high-momentum components in the $^4$He nucleus caused by inter-nucleon correlations using a variational ab initio approach, providing analytical derivations and confirming tensor correlation effects around 2 fm$^{-1}$.

Contribution

It introduces a comprehensive variational method (TO-HMAMD) for analyzing high-momentum components in $^4$He from bare nucleon-nucleon interactions, with new analytical derivations and detailed correlation analysis.

Findings

High-momentum components agree with experimental data up to high momentum.

Tensor correlations are explicitly confirmed around 2 fm$^{-1}$.

Different nucleon interactions show the manifestation of tensor correlations.

Abstract

High-momentum components of nuclei are essential for understanding the underlying inter-nucleon correlations in nuclei. We perform the comprehensive analysis for the origin of the high-momentum components of $^4$He in the framework of Tensor-optimized High-momentum Antisymmetrized Molecular Dynamics (TO-HMAMD), which is a completely variational approach as an $ab$ $initio$ theory starting from the bare nucleon-nucleon ($NN$) interaction. The analytical derivations are provided for the nucleon momentum distribution of the Antisymmetrized Momentum Dynamics (AMD) wave functions, with subtraction of center-of-mass motion. The nucleon momentum distribution for $^4$He is calculated by applying a new expansion technique to our $ab$ $initio$ wave function, and agrees with the values extracted from experimental data up to the high-momentum region. Fine-grained analysis is performed for the high-momentum components in $^4$He with respect to different nucleon correlations. Contributions from tensor, central with short-range, and many-body correlations are extracted from the nucleon momentum distributions. The manifestation of tensor correlation around 2 fm$^{-1}$ region is explicitly confirmed by comparing the momentum distributions predicted using different types of $NN$ interactions with and without the tensor force.