Nuclear Theory·nucl-th

Thursday·February 22, 2024

15 papers—8 primary·7 cross-listed

01
Behavior of the continuum coupling correlation energy in the vicinity of the particle emission threshold -- Gamow shell model study
J. P. Linares Fernandez🇺🇸 · N. Michel🇨🇳 · M. Płoszajczak🇫🇷
The Gamow shell model provides the open quantum system formulation of nuclear shell model. In the coupled-channel representation, Gamow shell model provides the unified theory of nuclear structure and reactions which is well suited for the study of resonances and clusterization. In this work, we apply this approach to study the continuum-coupling correlation energy for selected near-threshold states of $^{7}$ Li, $^{7}$ Be, using a translationally invariant Hamiltonian with an effective finite-range two-body interaction.
nucl-thEPJ Web Conf.(2024)·0 citations
02
Spin-Triplet Pairing in Heavy Nuclei is Stable Against Deformation
G. Palkanoglou · M. Stuck · A. Gezerlis
Any experimental evidence of nucleons paired in spin-triplet states will confirm the existence of an exotic phase of nuclear matter. This type of nuclear superfluidity has been hypothesized in heavy nuclei, where the antagonizing spin-orbit effects are damped, and there it oftentimes coexists with traditional spin-singlet pairing, leading to the possibility of mixed-spin pairing. Realistic nuclear deformation, not considered in such studies, could make-or-break these proposals, since its effect on triplet-pairing, and the competition (and coexistence) of the two superfluid phases, was expected to be crucial. We report on a thorough study on the effect of deformation on triplet-, singlet-, and mixed-spin pairing in the relevant region of the nuclear chart. We find that, at low isospin asymmetries, spin-triplet pairing is enhanced by deformation, while below the proton-drip line, the novel superfluid phase survives alongside the usual spin-singlet pairing. These results suggest that spin-triplet superfluidity exists in realistic nuclei and can be probed in the lab.
nucl-thcond-mat.supr-conPRL(2025)·13 citations
03
Low-energy dipole strength in 8He
Francesca Bonaiti · Sonia Bacca
In this work, we present new ab initio coupled-cluster calculations of dipole-excited state properties of 8He based on the chiral effective field theory interaction 1.8/2.0 (EM). We focus on the dipole polarizability, and compare the results to our previous study [Phys. Rev. C 105, 034313 (2022)] and subsequent theoretical work. With the aim of connecting the presence of low-lying dipole strength to structure properties of 8He, we compute the point-neutron radius, finding excellent agreement with available experimental data, and investigate its correlation with the dipole polarizability.
nucl-thnucl-exFew Body Syst.(2024)·5 citations
04
Double Scattering in Deuteron Electrodisintegration
Werner U Boeglin🇺🇸 · Misak M Sargsian🇺🇸
We demonstrate that at sufficiently high energies where the eikonal regime is established for hadronic interactions, the double scattering subprocess can be clearly identified and isolated in quasi-elastic deuteron electro-disintegration processes. Comparing theoretical calculations with the recent high precision experimental data we present a ``proof of principle" that these processes can be used to study advanced issues related to hadron formation in QCD. In this case, the double scattering represents as a fermi-scale ``detector" which probes products of high $Q^{2}$ scattering from the bound nucleon through their rescattering from the spectator nucleon in the deuteron.
nucl-thnucl-exPLB(2024)·5 citations
05
Non-nucleonic degrees of freedom and the spin structure of the deuteron
Misak M Sargsian🇺🇸
Electro-disintegration of the deuteron at large $Q^{2}$ currently represents on of the most promising reactions which allows to probe the bound nuclear state at internal momenta comparable to the rest mass of the nucleon. Large internal momentum in this case makes non-nuncleonic states energetically more feasible and the question that we address is what are the signatures that will indicate the existence of such states in the ground state of the nuclear wave function. To probe such states we developed a light-front formalism for relativistic description of a composite pseudo-vector system in which emerging proton and neutron are observed in electro-disintegration reaction. In leading high energy approximation our calculations show the possibility of the existence of a new ``incomplete" P-state-like structure in the deuteron at extremely large internal momenta. The incompleteness of the observed P-state violates the angular condition for the momentum distribution, which can happen only if the deuteron contains non-nucleonic structures, such as $ΔΔ$ , $N^{*} N$ or hidden color components. Because such states have distinctive angular momentum ( $l = 1$ ) they significantly modify the polarization properties of the deuteron wave function. As a result in addition to angular anisotropy of the LF momentum distribution of the nucleon in the deuteron one predicts strong modification of the tensor polarization asymmetry of the deuteron beyond the S- and D- wave predictions at large internal momenta in the deuteron.
nucl-thhep-phnucl-exPoS(2024)·0 citations
06
Kaon production in the HADES experiment in Au+Au collisions at $s_{NN} = 2.4$ GeV
Gao-Feng Wei🇨🇳 · Yu-Liang Zhao🇨🇳
Within an isospin- and momentum-dependent transport model by including the kaon reaction channels, we study the kaon prodution in heavy-ion collisions (HICs) at SIS (Darmstadt Schwerionen Synchrotron, GSI) energies. Based on simulations of a centrality of 0-40% Au + Au collision at $s_{N N} = 2.4$ GeV, a typical reaction that has been carried out by the HADES Collaboration, we confirm that the medium modification of kaon masses plays a vital role in studying the kaon productions in HICs, and is also unavoidable for the successful interpretation of the HADES data on kaon rapidity distributions and transverse mass spectra. Moreover, it is shown that the directed flows of kaons are affected significantly by the kaon potential and slightly affected by the medium modification of kaon masses. Also, the rapidity-dependent inverse slope parameter $T_{B}$ of the kaon transverse mass spectra is shown to be affected considerably by both the kaon potential and medium modification of kaon masses. However, through checking the simulations of related reactions in FOPI and/or KaoS experiments, some of these regular effects do not seem to be obvious and appear to be the reaction system and/or beam energy dependent. Nevertheless, it can be confirmed that the medium modification of kaon masses is favored by observations from the inverse slope parameter $T_{B}$ and transverse mass spectra of kaons in both HADES Au + Au collisions at $s_{N N} = 2.4$ GeV and FOPI Ni + Ni collisions at 1.93\textit{A} GeV. Therefore, measurements of the inverse slope parameter $T_{B}$ of kaon transverse mass spectra and the kaon directed flows in HADES Au + Au collisions would be great benefit to detection of the kaon potential and the corresponding medium effects on kaon masses.
nucl-thnucl-exPRC(2024)·3 citations
07
Theoretical analysis and predictions for the double electron capture of $^{124}$ Xe
Ovidiu Niţescu🇸🇰 · Stefan Ghinescu🇷🇴 · Vasile-Alin Sevestrean🇷🇴 · Mihai Horoi🇷🇴 · Fedor Šimkovic🇸🇰 · Sabin Stoica🇷🇴
We provide a complete theoretical description of the two-neutrino electron capture in $^{124}$ Xe, improving both the nuclear and the atomic structure calculations. We improve the general formalism through the use of the Taylor expansion method, leading to higher order terms in the decay rate of the process. The nuclear part is treated with pn-QRPA and interacting shell model (ISM) methods. The nuclear matrix elements (NMEs) are calculated with the pn-QRPA method with spin restoration by fixing the input parameters so that the experimental decay rate is reproduced, resulting in values significantly lower than in previous calculations. The validity of the pn-QRPA NMEs is tested by showing their values to be comparable with the ones for double-beta decay with emission of two electrons of $^{128, 130}$ Te, which have similar pairing features. Within the ISM, we reproduce the total experimental half-life within a factor of two and predict the capture fraction to the KK channel of about 74\%. We also predict the capture fractions to other decay channels and show that for the cumulative decay to the $K L_{1}$ - $K O_{1}$ channels, a capture fraction of about 24\% could be observed experimentally. On the atomic side, calculations are improved by accounting for the Pauli blocking of the decay of innermost nucleon states and by considering all $s$ -wave electrons available for capture, expanding beyond the K and L $_{1}$ orbitals considered in previous studies. We also provide improved atomic relaxation energies of the final atomic states of $^{124}$ Te, which may be used as input for background modeling in liquid Xenon experiments.
nucl-thJ.Phys.G(2024)·15 citations
08
Uncovering the sign of nuclear deformations: Determination of prolate or oblate shape via low-energy $α$ inelastic scattering
Shin Watanabe · Yoshiki Suzuki · Masaaki Kimura · Kazuyuki Ogata
Background: Understanding nuclear shape is a crucial problem in nuclear physics. In particular, determining the sign of quadrupole deformation, i.e., whether prolate or oblate, remains a challenging problem. Purpose: Our aim is to propose a method for determining the sign of quadrupole deformation using $α$ inelastic scattering data and to demonstrate its effectiveness. Method: Our approach is the standard coupled-channel method based on the macroscopic model. We utilize the nuclear reorientation effect, a phenomenon associated with the self coupling of excited states, as a probe sensitive to the sign of deformation. Results: We first provide an overview of how the reorientation effect influences inelastic scattering cross sections, and numerically confirm its validity in realistic cases. We then demonstrate that the sign of deformation can be uniquely determined from inelastic scattering cross section data. Conclusion: Our technique offers a systematic approach for determining the sign of deformation in both stable and unstable nuclei. The broad applicability of $α$ inelastic scattering will make it a valuable tool to study shape of nuclei, especially unstable nuclei.
nucl-thPRC(2024)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE