Phase-space distributions of nuclear short-range correlations

W Cosyn,J Ryckebusch

doi:10.1016/j.physletb.2021.136526

W Cosyn, J Ryckebusch

Open Access

https://doi.org/10.1016/j.physletb.2021.136526

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Abstract

Nuclear short-range correlations (SRCs) induce high-momentum/high-energy fluctuations in the nuclear medium. In order to assess their impact on nuclear bulk properties, like nuclear radii and kinetic energies, it is instrumental to determine how SRCs are distributed in phase space as this sheds light on the connection between their appearance in coordinate and momentum space. Using the lowest-order correlation operator approximation (LCA) to include SRC, we compute two-dimensional nuclear Wigner quasiprobability distributions w(r,k) to locate those (r,k) phase-space regions that are most heavily impacted by SRCs. The SRC-induced high-momentum components find their origin in a radial range that is confined to the nuclear interior. Significant SRCs strength is generated in the full momentum range 0≤k≲5fm−1 covered in this work, but below the Fermi momentum those are dwarfed by the mean-field contributions. As an application of w(r,k), we focus on the radial dependence of the kinetic energy T and the momentum dependence of the radius rrms for the symmetric nuclei C12, Ca40 and the asymmetric nucleus Ca48. The kinetic energy almost doubles after including SRCs, with the largest increase occurring in the nuclear interior r≲2 fm. The momentum dependence of the rrms teaches that the largest contributions stem from k≲2 fm−1, where the SRCs induce a slight reduction of the order of a few percent. The SRCs systematically reduce the Ca48 neutron skin by an amount that can be 10%.

Highlights

The size of an atomic nucleus [1,2] and how protons and neutrons are spatially arranged for various proton-to-neutron ratios [3,4,5,6] are topics of continued great interest in the precision era of nuclear physics
As we quantify the effect of short-range correlations (SRCs) on nuclear radii in this work and wish to quantify uncertainties stemming from the model parameters, we explore other values of c1, c2 by fitting them to the measured nuclear rms charge radii of 4He, 9Be, 12C, 16O, 27Al, 40Ca, 48Ca, 56Fe, 108Ag, 197Au and 208Pb [39]
The IPM corresponds with the HO model that can be formally reached after setting all correlation operators equal to zero in lowest-order correlation operator approximation (LCA)

Summary

Introduction

The size of an atomic nucleus [1,2] and how protons and neutrons are spatially arranged for various proton-to-neutron ratios [3,4,5,6] are topics of continued great interest in the precision era of nuclear physics. Wigner distributions [8,9] provide a distinct view on the spatial and momentum structure of quantum systems and are widely applicable including in subatomic physics [10]. It is a subject of great interest in non-perturbative quantum chromodynamics (QCD) [11,12,13,14,15,16,17,18]. With the Wigner distributions one gains access to the momentum structure of radii and the spatial structure of the kinetic energy, and how those are impacted by SRCs. Alternate approaches [35] have addressed the SRCs in both coordinate and momentum space. Those distributions form the basis to elucidate the phase-space dependence of SRCs in the proton and neutron radii and kinetic energies

Formalism

Results

Conclusion and outlook