Nuclear Theory·nucl-th

Friday·May 5, 2023

8 papers—4 primary·4 cross-listed

01
[Submitted on 4 May 2023]
Light nuclei production in Au+Au collisions at $s_{N N} = 3$ GeV from coalescence model
Yue Xu🇨🇳 · Xionghong He🇨🇳 · Nu Xu🇨🇳
The nucleon coalescence model is one of the most popular theoretical models for light nuclei production in high-energy heavy-ion collisions. The production of light nuclei $d$ , $t$ , $^{3}$ He, and $^{4}$ He is studied using the transport model JAM with a simplified afterburner coalescence at $s_{N N} = 3$ GeV Au+Au collisions. We scan the cut-off of phenomenological coalescence parameters, the relative spatial distance $Δ R$ and momentum difference $Δ P$ , for formation of light nuclei by nucleon coalescence to reproduce the light nuclei $p_{T}$ spectra measured by STAR experiment. The results indicate a potential connection between the coalescence parameters and the binding energy as well as the diameter of these light nuclei.
Comments:
to be published in Chinese Physics C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2305.02487 [pdf]
CPC(2023)·5 citations
02
[Submitted on 4 May 2023]
Probabilistic neural networks for improved analyses with phenomenological models
C.H. Kim · K.Y. Chae · M.S. Smith · D.W. Bardayan · C.R. Brune · R.J. deBoer · D. Lu · D. Odell
Physics models typically contain adjustable parameters to reproduce measured data. While some parameters correspond directly to measured features in the data, others are unobservable. These unobservables can, in some cases, cause ambiguities in the extraction of observables from measured data, or lead to questions on the physical interpretation of fits that require these extra parameters. We propose a method based on deep learning to extract values of observables directly from the data without the need for unobservables. The key to our approach is to label the training data for the deep learning model with only the observables. After training, the deep learning model can determine the values of observables from measured data with no ambiguities arising from unobservables. We demonstrate this method on the phenomenological R-matrix that is widely utilized in nuclear physics to extract resonance parameters from cross section data. Our deep learning model based on Transformers successfully predicts nuclear properties from measurements with no need for the channel radius and background pole parameters required in traditional R-matrix analyses. Details and limitations of this method, which may be useful for studies of a wide range of phenomena, are discussed.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2305.02623 [pdf]
PRC(2024)·3 citations
03
[Submitted on 4 May 2023]
Collapse of the $N = 28$ shell closure in the newly discovered $^{39}$ Na and the development of deformed halos towards the neutron dripline
K. Y. Zhang · P. Papakonstantinou · M.-H. Mun · Y. Kim · H. Yan · X.-X. Sun
Halos and changes of nuclear magicities have been extensively investigated in exotic nuclei during past decades. The newly discovered $^{39}$ Na with the neutron number $N = 28$ provides a new platform to explore such novel phenomena near the neutron dripline of the sodium isotopic chain. We study the shell property and the possible halo structure in $^{39}$ Na within the deformed relativistic Hartree-Bogoliubov theory in continuum. It is found that the lowering of $2 p$ orbitals in the spherical limit results in the collapse of the $N = 28$ shell closure in $^{39}$ Na, and a well deformed ground state is established. The pairing correlations and the mixing of $p f$ components driven by deformation lead to the occupation of weakly bound or continuum $p$ -wave neutron orbitals. An oblate halo is therefore formed around the prolate core in $^{39, 41}$ Na, making $^{39}$ Na a single nucleus with the coexistence of several exotic structures, including the quenched $N = 28$ shell closure, Borromean structure, deformed halo, and shape decoupling. The microscopic mechanisms behind the shape decoupling phenomenon and the development of halos towards dripline are revealed.
Comments:
8 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2305.02636 [pdf]
PRC(2023)·58 citations
04
[Submitted on 4 May 2023]
Kinetic approach of light-nuclei production in intermediate-energy heavy-ion collisions
Rui Wang · Yu-Gang Ma · Lie-Wen Chen · Che Ming Ko · Kai-Jia Sun · Zhen Zhang
We develop a kinetic approach to the production of light nuclei up to mass number $A$ $⩽$ $4$ in intermediate-energy heavy-ion collisions by including them as dynamic degrees of freedom. The conversions between nucleons and light nuclei during the collisions are incorporated dynamically via the breakup of light nuclei by a nucleon and their inverse reactions. We also include the Mott effect on light nuclei, i.e., a light nucleus would no longer be bound if the phase-space density of its surrounding nucleons is too large. With this kinetic approach, we obtain a reasonable description of the measured yields of light nuclei in central Au+Au collisions at energies of $0.25$ - $1.0 A GeV$ by the FOPI collaboration. Our study also indicates that the observed enhancement of the $α$ -particle yield at low incident energies can be attributed to a weaker Mott effect on the $α$ -particle, which makes it more difficult to dissolve in nuclear medium, as a result of its much larger binding energy.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2305.02988 [pdf]
PRC(2023)·48 citations
05
[Submitted on 3 May 2023] (cross-list from hep-ph)
Searching for the baryon-to-meson transition region with the MPD at NICA
Alejandro Ayala🇲🇽 · Wolfgang Bietenholz🇲🇽 · Eleazar Cuautle🇲🇽 · Rodrigo García Formentí🇲🇽 · Rodrigo Guzmán🇲🇽
In heavy-ion reactions, statistical models predict a rapid change in the baryon-to-meson ratio as a function of the collision energy. This change occurs when the hadronic medium transits from a baryon- to a meson-dominated gas. The transition is expected to take place at a temperature around 140 MeV and a baryon chemical potential around 420 MeV, corresponding to a center-of-mass collision energy of $s_{N N} ≃ 8.2$ GeV. The energy range of the MPD experiment will be suitable for the exploration of this transition region. We present preliminary results of feasibility studies for the measurement of the transverse momentum spectra for mesons and baryons, using Monte Carlo data samples, in order to study the crossing point between these transverse momenta, as a function of the centrality and collision energy.
Comments:
5 pages, LaTex, 5 figures, to appear in Phys. At. Nucl
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2305.02455 [pdf]
Phys.Atom.Nucl.(2023)·5 citations
06
[Submitted on 4 May 2023] (cross-list from hep-ph)
Exotic spin-dependent interactions through unparticle exchange
L. Y. Wu🇨🇳 · K. Y. Zhang🇨🇳 · H. Yan🇨🇳
The potential discovery of unparticles could have far-reaching implications for particle physics and cosmology. For over a decade, high-energy physicists have extensively studied the effects of unparticles. In this study, we derive six types of nonrelativistic potentials between fermions induced by unparticle exchange in coordinate space. We consider all possible combinations of scalar, pseudo-scalar, vector, and axial-vector couplings to explore the full range of possibilities. Previous studies have only examined scalar-scalar (SS), pseudoscalar-pseudoscalar (PP), vector-vector (VV), and axial-axial-vector (AA) type interactions, which are all parity even. We propose SP and VA interactions to extend our understanding of unparticle physics, noting that parity conservation is not always guaranteed in modern physics. We explore the possibilities of detecting unparticles through the long-range interactions they may mediate with ordinary matter. Dedicated experiments using precision measurement methods can be employed to search for such interactions. We discuss the properties of these potentials and estimate constraints on several coupling constants based on existing experimental data. Our findings indicate that the coupling between vector unparticles and fermions is constrained by up to 9 orders of magnitude more tightly than the previous limits.
Comments:
15 pages, 1 figure, 1 table; References updated
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2305.02628 [pdf]
JHEP(2024)·4 citations
07
[Submitted on 4 May 2023] (cross-list from hep-ph)
Bound state solutions of the Schrödinger equation for dibaryons via asymptotic iteration method
Nazanin Shiri🇮🇷 · Narges Tazimi🇮🇷 · Majid Monemzadeh🇮🇷
Conventionally, hexaquarks are claimed to be exotic particles, most of which have not yet been experimentally detected. In this work, we study the mass spectra of exotic hadrons known as hexaquarks in the form of dibaryons. We investigate the hexaquark states with the twobody configuration in more detail. Starting from the analytical solution of the radial Schrödinger equation for the Hulthén potential in the framework of the asymptotic iteration method (AIM), we obtain the binding energy and mass spectrum of charm and bottom hexaquarks for different spin states. We strongly recommend searching experimentally for double charm and bottom dibaryons in the future.
Comments:
27 pages, 3 figures,. arXiv admin note: text overlap with arXiv:math-ph/0609010 by other authors
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2305.02716 [pdf]
5 citations
08
[Submitted on 4 May 2023] (cross-list from hep-ph)
Quarkonium spin alignment in a vortical medium
Paulo Henrique De Moura🇧🇷 · Kayman J. Goncalves🇧🇷 · Giorgio Torrieri🇧🇷
We use a potential model to investigate the phenomenology of quarkonium in a thermal rotating medium, where vorticity and spin density are not necessarily in equilibrium. We find that the quarkonium spin density matrix, as well as the binding energy and melting temperature, are sensitive to both the vorticity and the lack of equilibrium between vorticity and spin. This means that quarkonium spin alignment is a sensitive probe for vorticity and spin within the hydrodynamic phase. Information unequivocably pointing to spin-orbit non-equilibrium dynamics can be obtained from a combined study of quarkonium relative abundance and spin alignment, as well as experimentally obtainable off-diagonal density matrix elements.
Comments:
Version accepted for publication, Phys.Rev.D. arXiv admin note: text overlap with arXiv:2205.15087
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2305.02985 [pdf]
PRD(2023)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE