Nuclear Theory·nucl-th

Thursday·November 16, 2023

11 papers—6 primary·5 cross-listed

01
Four-body bound states in momentum space: the Yakubovsky approach without two-body $t -$ matrices
M. Mohammadzadeh · M. Radin · K. Mohseni · M. R. Hadizadeh
This study presents a solution to the Yakubovsky equations for four-body bound states in momentum space, bypassing the common use of two-body $t -$ matrices. Typically, such solutions are dependent on the fully-off-shell two-body $t -$ matrices, which are obtained from the Lippmann-Schwinger integral equation for two-body subsystem energies controlled by the second and third Jacobi momenta. Instead, we use a version of the Yakubovsky equations that doesn't require $t -$ matrices, facilitating the direct use of two-body interactions. This approach streamlines the programming and reduces computational time. Numerically, we found that this direct approach to the Yakubovsky equations, using 2B interactions, produces four-body binding energy results consistent with those obtained from the conventional $t -$ matrix dependent Yakubovsky equations, for both separable (Yamaguchi and Gaussian) and non-separable (Malfliet-Tjon) interactions.
nucl-thphysics.comp-phquant-phFront.in Phys.(2023)·3 citations
02
Parameters of nucleon densities and the Coulomb barrier in heavy-ion collisions
Makar Simonov (1 and 2 and 3) · Alexander Karpov (2 and 4) · Tatiana Tretyakova (2 and 3) ((1) II. Physikalisches Institut, Justus-Liebig-Universität Gießen, Gießen, Germany, (2) Joint Institute for Nuclear Research, Dubna, Russia, (3) Lomonosov Moscow State University, Moscow, Russia, (4) Dubna State University, Dubna, Russia)
When modeling nuclear processes which occur in heavy-ion reactions, it is necessary to calculate the potential energy of interaction between two nuclei. One of the main features determining the dynamics of the nucleus-nucleus collision is the Coulomb barrier, the knowledge of which is especially important when low- and intermediate-energy reactions are being studied. Our goal is to establish a parameterization of nucleon density distributions for calculation of the nucleus-nucleus double-folding potential in nuclear reactions. Special attention is paid to the description of the Coulomb barrier. The study analyzes experimental data on charge radii, diffuseness, and neutron skin thickness of atomic nuclei. The nucleus-nucleus potential is calculated in the framework of the double-folding method with the effective nucleon-nucleon interaction taken in the form of the zero-range Migdal potential. Based on this analysis and comparison with the Bass potential, parameters of nucleon density distributions are fitted to reproduce the Coulomb barrier. A method for correcting the parameters of nucleon densities to reproduce the Coulomb barrier with the double-folding potential is proposed. The presented way to correct nucleon densities allows obtaining a satisfactory description of the Coulomb barrier that is important for modeling near-barrier collisions of heavy ions.
nucl-th0 citations
03
Role of the isospin diffusion on cluster transfer in $^{12, 14}$ C + $^{209}$ Bi reactions
Zepeng Gao · Yinu Zhang · Long Zhu · Zehong Liao · Yu Yang · Chenchen Guo · Jun Su
Heavy-ion collisions at near-barrier energies provide a crucial pathway for investigating nucleon correlations and clustering structures. Recent experimental results showed that the valence neutrons in light projectiles obviously enhance the $α$ transfer. This finding is extremely puzzled and fascinating, because it violates the ground-state $Q$ value systematics unexpectedly. In this work, the time-dependent Hartree-Fock approach is utilized to investigate the cluster transfer. By comparing the reactions $^{12, 14}$ C + $^{209}$ Bi, we discover that above puzzling behavior is because of the strong correlation between isospin diffusion and clustering. Our calculations clearly show that the equilibrium of neutron-to-proton ratio strongly inhibits the clustering. This work opens a prospect for investigating the clustering in open quantum system.
nucl-thPRC(2024)·5 citations
04
Effective Range Approximation in Variable Phase Approach for Triplet $^{3} S_{1}^{{n p}}$ and Singlet $^{1} S_{0}^{{nn, n p, pp}}$ State
Anil Khachi
This work is a short communication where phase function method has been applied to obtain the phase shifts using Effective Range Approximation potential for $^{3} S_{1} - n p$ , $^{1} S_{0} - nn$ , $^{1} S_{0} - n p$ , and $^{1} S_{0} - pp$ states. No free fitting parameters are used in calculations and reasonably good match with the experimental phase shifts is observed for E $\leq$ 20 MeV. Potentials are obtained for n-n, n-p, and p-p scattering that are exponential well-shaped.
nucl-thRom.J.Phys.(2025)·2 citations
05
Constraints on Density Dependent MIT Bag Model Parameters for Quark and Hybrid Stars
Soumen Podder🇮🇳 · Suman Pal🇮🇳 · Debashree Sen🇰🇷 · Gargi Chaudhuri🇮🇳
We compute the equation of state (EoS) of strange quark stars (SQSs) with the MIT Bag model using density dependent bag pressure, characterized by a Gaussian distribution function. The bag pressure's density dependence is controlled by three key parameters namely the asymptotic value ( $B_{a s}$ ), $Δ B (= B_{0} - B_{a s})$ , and $β$ . We explore various parameter combinations ( $B_{a s}$ , $Δ B$ , $β$ ) that adhere to the Bodmer-Witten conjecture, a criterion for the stability of SQSs. Our primary aim is to analyze the effects of these parameter variations on the structural properties of SQSs. However we find that none of the combinations can satisfy the NICER data for PSR J0030+0451 and the constraint on tidal deformability from GW170817. So it can be emphasized that this model cannot describe reasonable SQS configurations. We also extend our work to calculate structural properties of hybrid stars (HSs). With the density dependent bag model (DDBM), these astrophysical constraints are fulfilled by the HSs configurations within a very restricted range of the three parameters. The present work is the first to constrain the parameters of DDBM for both SQS and HSs using the recent astrophysical constraints on tidal deformabiity from GW170817 and that on mass-radius relationship from NICER data.
nucl-thhep-phNPA(2024)·26 citations
06
Differential Rotation in Compact Objects with Hyperons and Delta Isobars
Delaney Farrell🇺🇸 · Fridolin Weber🇺🇸 · Jia Jie Li🇨🇳 · Armen Sedrakian🇩🇪
Neutron stars may experience differential rotation on short, dynamical timescales following extreme astrophysical events like binary neutron star mergers. In this work, the masses and radii of differentially rotating neutron star models are computed. We employ a set of equations of states for dense hypernuclear and $Δ$ -admixed-hypernuclear matter obtained within the framework of CDF theory in the relativistic Hartree-Fock (RHF) approximation. Results are shown for varying meson- $Δ$ couplings, or equivalently the $Δ$ -potential in nuclear matter. A comparison of our results with those obtained for non-rotating stars shows that the maximum mass difference between differentially rotating and static stars is independent of the underlying particle composition of the star. We further find that the decrease in the radii and increase in the maximum masses of stellar models when $Δ$ -isobars are added to hyperonuclear matter (as initially observed for static and uniformly rotating stars) persist also in the case of differentially rotating neutron stars.
nucl-thastro-ph.HEAstron.Nachr.(2024)·0 citations
07
Relaxation time for the alignment between quark spin and angular velocity in a rotating QCD medium
Alejandro Ayala🇲🇽 · Santiago Bernal-Langarica🇲🇽 · Isabel Domínguez Jiménez🇲🇽 · Ivonne Maldonado🇷🇺 · José Jorge Medina-Serna🇲🇽 · Javier Rendón🇲🇽 · María Elena Tejeda-Yeomans🇲🇽
We compute the relaxation times for massive quarks and anti-quarks to align their spins with the angular velocity in a rigidly rotating medium at finite temperature and baryon density. The rotation effects are implemented using a fermion propagator immersed in a cylindrical rotating environment. The relaxation time is computed as the inverse of the interaction rate to produce an asymmetry between the quark (anti-quark) spin components along and opposite to the angular velocity. For conditions resembling heavy-ion collisions, the relaxation times for quarks are smaller than for anti-quarks. For semi-central collisions the relaxation time is within the possible life-time of the QGP for all collision energies. However, for anti-quarks this happens only for collision energies $s_{N N} ≳ 50$ GeV. The results are quantified in terms of the intrinsic quark and anti-quark polarizations, namely, the probability to build the spin asymmetry as a function of time. Our results show that these intrinsic polarizations tend to 1 with time at different rates given by the relaxation times with quarks reaching a sizable asymmetry at a faster pace. These are key results to further elucidate the mechanisms of hyperon polarization in relativistic heavy-ion collisions.
↳ hep-phnucl-thPRD(2024)·8 citations
08
Pion distribution functions from low-order Mellin moments
Ya Lu🇨🇳 · Yin-Zhen Xu🇪🇸 · Khépani Raya🇪🇸 · Craig D. Roberts🇨🇳 · José Rodríguez-Quintero🇪🇸
Exploiting an evolution scheme for parton distribution functions (DFs) that is all-orders exact, contemporary lattice-QCD (lQCD) results for low-order Mellin moments of the pion valence quark DF are shown to be mutually consistent. The analysis introduces a means by which key odd moments can be obtained from the even moments in circumstances where only the latter are available. Combining these elements, one arrives at parameter-free lQCD-based predictions for the pointwise behaviour of pion valence, glue, and sea DFs, with sound uncertainty estimates. The behaviour of the pion DFs at large light-front momentum fraction, $x > 0.85$ , is found to be consistent with QCD expectations and continuum analyses of pion structure functions, i.e., damping like $(1 - x)^{β_{parton}}$ , with $β_{valence} \approx 2.4$ , $β_{glue} \approx 3.6$ , $β_{sea} \approx 4.6$ . It may be possible to test these predictions using data from forthcoming experiments.
↳ hep-phhep-exhep-latnucl-ex+1PLB(2024)·35 citations
09
Identification of a natural fieldlike entanglement resource in trapped-ion chains
Natalie Klco🇺🇸 · D. H. Beck🇺🇸
The electromagnetic trapping of ion chains can be regarded as a process of non-trivial entangled quantum state preparation within Hilbert spaces of the local axial motional modes. To begin uncovering properties of this entanglement resource produced as a byproduct of conventional ion-trap quantum information processing, the quantum continuous-variable formalism is herein utilized to focus on the leading-order entangled ground state of local motional modes in the presence of a quadratic trapping potential. The decay of entanglement between disjoint subsets of local modes is found to exhibit features of entanglement structure and responses to partial measurement reminiscent of the free massless scalar field vacuum. With significant fidelities between the two, even for large system sizes, a framework is established for initializing quantum field simulations via "imaging" extended entangled states from natural sources, rather than building correlations through deep circuits of few-body entangling operators. By calculating probabilities in discrete Fock subspaces of the local motional modes, considerations are presented for locally transferring these pre-distributed entanglement resources to the qudits of ion internal energy levels, improving this procedure's anticipated experimental viability.
↳ quant-phhep-latnucl-thPRA(2024)·4 citations
10
Systematic study of the low-lying electric dipole strength in Sn isotopes and its astrophysical implications
M. Markova🇳🇴 · A. C. Larsen🇳🇴 · P. von Neumann-Cosel🇩🇪 · E. Litvinova🇺🇸 · A. Choplin🇧🇪 · S. Goriely🇧🇪 · S. Martinet🇧🇪 · L. Siess🇧🇪 · M. Guttormsen🇳🇴 · F. Pogliano🇳🇴 · S. Siem🇳🇴
The $γ$ -ray strength functions (GSF) and nuclear level densities (NLD) below the neutron threshold have been extracted for $^{111 - 113, 116 - 122, 124}$ Sn from particle- $γ$ coincidence data with the Oslo method. The evolution of bulk properties of the low-lying electric dipole response has been investigated on the basis of the Oslo GSF data and results of a recent systematic study of electric and magnetic dipole strengths in even-even Sn isotopes with relativistic Coulomb excitation. The obtained GSFs reveal a resonance-like peak on top of the tail of the isovector giant dipole resonance, centered at $\approx$ 8 MeV and exhausting $\approx$ 2\% of the classical Thomas-Reiche-Kuhn (TRK) sum. In contrast to predictions of the relativistic quasiparticle random-phase and time-blocking approximation calculations (RQRPA and RQTBA), no monotonous increase in the total low-lying $E 1$ strength was observed in the experimental data from $^{111}$ Sn to $^{124}$ Sn, demonstrating rather similar strength distributions in these nuclei. The Oslo GSFs and NLDs were further used as inputs to constrain the cross sections and Maxwellian-averaged cross sections of $(n, γ)$ reactions in the Sn isotopic chain using TALYS. The obtained results agree well with other available experimental data and the recommended values from the JINA REACLIB, BRUSLIB, and KADoNiS libraries. Despite relatively small exhausted fractions of the TRK sum rule, the low-lying electric dipole strength makes a noticeable impact on the radiative neutron-capture cross sections in stable Sn isotopes. Moreover, the experimental Oslo inputs for the $^{121, 123}$ Sn $(n, γ)$ $^{122, 124}$ Sn reactions were found to affect the production of Sb in the astrophysical $i$ -process, providing new constraints on the uncertainties of the resulting chemical abundances from multi-zone low-metallicity Asymptotic Giant Branch stellar models.
↳ nucl-exnucl-thPRC(2024)·23 citations
11
Breakdown of collinear factorization in the exclusive photoproduction of a $π^{0} γ$ pair with large invariant mass
Saad Nabeebaccus🇫🇷 · Jakob Schoenleber🇩🇪 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷
We study the exclusive photoproduction of a $π^{0} γ$ pair with large invariant mass $M_{γ π}^{2}$ , which is sensitive to the exchange of either two quarks or two gluons in the $t$ -channel. In this paper, we show that the process involving two-gluon exchanges does not factorize in the Bjorken limit at the leading twist. This can be explicitly demonstrated by the fact that there exist diagrams, which contribute at the leading twist, for which Glauber gluons are trapped, due to the pinching of the contour integration of both the plus and minus component of the Glauber gluon momentum. For the same reason, $π^{0}$ -nucleon scattering to two photons also suffers from the same issue. On the other hand, we stress that there are no issues with respect to collinear factorization for the quark channels. By considering an analysis of all potential reduced diagrams of leading pinch-singular surfaces, we argue that the quark channel is safe from Glauber pinches, and therefore, a collinear factorization in that case follows through without any problems. This means that processes where gluon exchanges are forbidden, such as the exclusive photoproduction of $π^{\pm} γ$ and $ρ^{0, \pm} γ$ , are unaffected by the factorization breaking effects we point out in this paper.
↳ hep-phnucl-thPRD(2025)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE