Nuclear Theory·nucl-th

Monday·May 16, 2022

7 papers—3 primary·4 cross-listed

01
[Submitted on 12 May 2022]
Dibaryon resonances and short-range $N N$ interaction
V.I. Kukulin🇷🇺 · V.N. Pomerantsev🇷🇺 · O.A. Rubtsova🇷🇺 · M.N. Platonova🇷🇺 · I.T. Obukhovsky🇷🇺
The dibaryon concept for the nuclear force is presented, assuming that the main attraction between the nucleons at medium distances is determined by the $s$ -channel exchange of an intermediate six-quark (dibaryon) state. To construct the respective $N N$ interaction model, a microscopic six-quark description of the $N N$ system is used, in which symmetry aspects play a special role. It is shown that the $N N$ interaction in all important partial waves can be described properly by a superposition of the long-range $t$ -channel one-pion exchange and the $s$ -channel exchange by an intermediate dibaryon. The developed model gives a good description of both elastic phase shifts and inelasticities of $N N$ scattering in all $S$ , $P$ , $D$ and $F$ partial waves at energies from zero to 600 - 800 MeV and even higher.The parameters of the intermediate six-quark states corresponding to the best fit of $N N$ scattering data are found to be consistent with the parameters of the known dibaryon resonances in those $N N$ partial configurations where their existence has been experimentally confirmed. Predictions for new dibaryon states are given as well.
Comments:
23 pages, 9 figures; version accepted to Chinese Physics C with updated references
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2205.06377 [pdf]
CPC(2022)·14 citations
02
[Submitted on 13 May 2022]
R-matrix analysis of elastic scattering, phase shift and radiative capture reaction cross sections in the $α + α$ system
Suprita Chakraborty · Rajkumar Santra · Subinit Roy · V.M. Datar
The unstable nucleus $^{8}$ Be, with its two $α$ -cluster configuration, is the doorway to the formation of heavier $α$ -cluster nuclei. Most importantly, its the precursor of the production of $^{12}$ C through the Hoyle state, a resonance state of three $α$ clusters, in the helium burning phase of a massive star. The nucleus exhibits a ground state band of rotational states established through $α - α$ scattering experiments. A subsequent precision particle- $γ$ coincidence measurement of the electromagnetic transition between the 4 $^{+} \to$ 2 $^{+}$ excited states also corroborated the evidence for a highly deformed dumb-bell shaped structure of $^{8}$ Be. A simultaneous phenomenological R-matrix analysis of the measured capture reaction cross sections along with the elastic excitation function and phase shift data has been performed. The resulting reduced transition strength of 21.96 $\pm$ 3.86 $e^{2} f m^{4}$ compares well with the estimated experimental value of 21.0 $\pm$ 2.3 e $^{2}$ fm $^{4}$ . The R-matrix yield of the B( $E 2$ ) value is closer to the prediction of cluster model but about 19 $%$ less than the {\it ab initio} result.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2205.06488 [pdf]
PRC(2022)·3 citations
03
[Submitted on 13 May 2022]
The quasi-deuteron model at low RG resolution
A. J. Tropiano · S. K. Bogner · R. J. Furnstahl · M. A. Hisham
The quasi-deuteron model introduced by Levinger is used to explain cross sections for knocking out high-momentum protons in photo-absorption on nuclei. This is within a framework we characterize as exhibiting high renormalization group (RG) resolution. Assuming a one-body reaction operator, the nuclear wave function must include two-body short-range correlations (SRCs) with deuteron-like quantum numbers. In a previous paper, we showed that SRC physics can be naturally accounted for at low RG resolution. Here we describe the quasi-deuteron model at low RG resolution and determine the Levinger constant, which is proportional to the ratio of nuclear photo-absorption to that for photo-disintegration of a deuteron. We extract the Levinger constant based on the ratio of momentum distributions at high relative momentum. We compute momentum distributions evolved under similarity RG (SRG) transformations, where the SRC physics is shifted into the operator as a universal two-body term. The short-range nature of this operator motivates using local-density approximations with uncorrelated wave functions in evaluating nuclear matrix elements, which greatly simplifies the analysis. The operator must be consistently matched to the RG scale and scheme of the interaction for a reliable extraction. We apply SRG transformations to different nucleon-nucleon (NN) interactions and use the deuteron wave functions and Weinberg eigenvalues to determine approximate matching scales. We predict the Levinger constant for several NN interactions and a wide range of nuclei comparing to experimental extractions. The predictions at low RG resolution are in good agreement with experiment when starting with a hard NN interaction and the initial operator. Similar agreement is found using soft NN interactions when the additional two-body operator induced by evolution from hard to soft is included.
Comments:
8 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.06711 [pdf]
PRC(2022)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE

Dibaryon resonances and short-range NN interaction

R-matrix analysis of elastic scattering, phase shift and radiative capture reaction cross sections in the α+α system

The quasi-deuteron model at low RG resolution

Affiliations

Dibaryon resonances and short-range $N N$ interaction

R-matrix analysis of elastic scattering, phase shift and radiative capture reaction cross sections in the $α + α$ system