Nuclear Theory·nucl-th

Wednesday·March 6, 2024

15 papers—10 primary·5 cross-listed

01
[Submitted on 4 Mar 2024]
Shell Effects in Quasi-fission in Reactions Forming 226Th Compound Nucleus
Hyeonseop Lee · Patrick McGlynn · Cedric Simenel
Quasi-fission (QF) reactions occur in fully damped heavy-ion collisions without the formation of an equilibrated compound nucleus, leading to the formation of fragments with similar properties as in fission reactions. Similar shell effects are expected to affect fragment formation in both fission and QF. Our purpose is to investigate QF dynamics in different reactions forming the same compound nucleus and search for possible signatures of shell effects in fragment formation. 50Ca+176Yb and 96Zr+130Sn QF reactions are simulated with the time-dependent Hartree-Fock code Sky3D near the Coulomb barrier. Evolutions of the quadrupole (Q20) and octupole (Q30) moments are interpreted in terms of features of the potential energy surface (PES) of the 226Th compound nucleus. Both reactions encounter QF. In 50Ca+176Yb, those only occur at finite angular momenta. In the more symmetric 96Zr+130Sn reaction with stronger Coulomb repulsion in the entrance channel, QF also occurs in central collisions. In agreement with earlier predictions, 50Ca+176Yb encounters partial mass equilibration that is stopped when the heavy fragment reaches Z~54 protons, as in the asymmetric fission mode of 226Th. 96Zr+130Sn encounters an inverse QF also leading to similar fragments as in asymmetric fission. In both systems, QF trajectories in the Q20-Q30 plane follow the asymmetric fission valley of 226Th PES. The observation of an inverse QF is a clear prediction that shell effects have a strong influence in QF. The similarity between fragments formed in asymmetric fission and QF supports the idea that the same shell effects are at play in both mechanisms. Interpreting QF dynamics with PES used in fission is naturally limited by the fact that these PES are usually computed with axial symmetry, no angular momentum and no excitation energy, thus motivating future developments of PES for QF.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2403.02541 [pdf]
PRC(2024)·14 citations
02
[Submitted on 5 Mar 2024]
Macroscopic neutrinoless double beta decay: long range quantum coherence
Gordon Baym🇺🇸 · Jen-Chieh Peng🇺🇸
We re-introduce, in light of our modern understanding of neutrinos, the concept of ``macroscopic neutrinoless double beta decay" (MDBD) for Majorana neutrinos. In this process an antineutrino produced by a nucleus undergoing beta decay, $X \to Y + e^{-} + ν ˉ_{e}$ , is absorbed as a neutrino by another identical $X$ nucleus via the inverse beta decay reaction, $ν_{e} + X \to e^{-} + Y$ . The distinct signature of MDBD is that the total kinetic energy of the two electrons equals twice the endpoint energy of single beta decay. The amplitude for MDBD, a coherent sum over the contribution of different mass states of the intermediate neutrinos, reflects quantum coherence over macroscopic distances, and is a new macroscopic quantum effect. We evaluate the rate of MDBD for a macroscopic sample of `` $X$ " material, e.g., tritium, acting both as the source and the target. The accidental background for MDBD originating from two separate single beta decays, which contains two final state neutrinos, can be readily rejected by measuring the energy of the detected two electrons. We discuss the similarities and differences between the MDBD and conventional neutrinoless double beta decay.
Comments:
11 pages, 6 figures, final version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2403.02602 [pdf]
NPB(2025)·1 citation
03
[Submitted on 5 Mar 2024]
Impact of (magneto-)thermoelectric effect on diffusion of conserved charges in hot and dense hadronic matter
He-Xia Zhang🇨🇳 · Ke-Ming Shen🇨🇳 · Yu-Xin Xiao🇨🇳 · Ben-Wei Zhang🇨🇳
We investigate the thermoelectric effect, which describes the generation of an electric field induced by temperature and conserved charge chemical potential gradients, in the hot and dense hadronic matter created in heavy-ion collisions. Utilizing the Boltzmann kinetic theory within the repulsive mean-field hadron resonance gas model, we evaluate both the diffusion thermopower matrix and diffusion coefficient matrix for the baryon number ( $B$ ), electric charge ( $Q$ ), and strangeness ( $S$ ). The Landau-Lifshitz choice for the rest frame of the fluid is enforced in the derivation. We find that the thermoelectric effect hinders the diffusion processes of multiple conserved charges, particularly reducing the coupling between electric charge and baryon number (strangeness) in baryon (strangeness) diffusion. Given that the repulsive mean-field interactions between hadrons have a significant effect on the diffusion thermopower matrix and diffusion coefficient matrix in the baryon-rich region, we extend the investigation to include the impact of magnetic fields, analyzing the magneto-thermoelectric effect on both the diffusion coefficient matrix and the Hall-like diffusion coefficient matrix. The sensitivities of the magnetic field-dependent diffusion thermopower matrix and magneto-thermoelectric modified diffusion coefficient matrix to the choices of various transverse conditions are also studied.
Comments:
21 pages, 12 figures, Version accepted by Phys. Rev. D
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2403.02705 [pdf]
PRD(2024)·4 citations
04
[Submitted on 5 Mar 2024]
Nuclear medium effects on the properties of $Λ (1405)$
J. Y. Süngü🇹🇷 · N. Er🇹🇷
We study the $Λ (1405)$ resonance with $I (J^{P}) = 0 (1/ 2^{-})$ in the context of the pentaquark hypothesis in the nuclear medium. For the investigation of the influence of the nuclear medium on the physical parameters of $Λ (1405)$ , we propose a molecular-type structure involving $K^{-} p$ and $K ˉ^{0} n$ admixtures, correlated with the nuclear matter density. Our analysis reveals a substantial shift in both mass and residue, approximately $20%$ and $38%$ , respectively. These findings have significant implications for experimental researchers aimed at identifying in-medium characteristics of hyperon resonances.
Comments:
15 pages, 6 graphs, 3 table
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2403.02728 [pdf]
J.Phys.G(2024)·4 citations
05
[Submitted on 5 Mar 2024]
Relativistic energy density functional from momentum space to coordinate space within a coherent density fluctuation model
Praveen K. Yadav · Raj Kumar · M. Bhuyan
In this theoretical study, we have derived a simplified analytical expression for the binding energy per nucleon as a function of density and isospin asymmetry within the relativistic mean-field model. We have generated a new parameterization for the density-dependent DD-ME2 parameter set using the Relativistic-Hartree-Bogoliubov approach. Moreover, this work attempts to revisit the prior polynomial fitting in [Phy. Rev. C 103, 024305 (2021)] for the non-linear NL3 force parameter to provide a simplified set of equations for the energy density functional which is used for calculating the surface properties of finite nuclei. The current study improves the existing fitting procedure by effectively proposing a simpler model that provides comparably precise results while lowering the computational expense. To study the surface properties of finite nuclei with these parameterizations, we have adopted the coherent density fluctuation model, which effectively translates the quantities of nuclear matter from momentum space to coordinate space at local density. The isospin properties, such as symmetry energy and its surface and volume components, slope parameter, finite nuclear incompressibility, and surface incompressibility for even-even nuclei, are calculated for different mass regions. Moreover, we have studied the effect of density, weight function, and choice of relativistic force parameters on the surface properties. The consequence of this work will help to determine the properties of nuclei along the nuclear landscape and can facilitate an improved understanding of the island of stability, heavy-ion collision, and nucleosynthesis, among others.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2403.02729 [pdf]
EPL(2024)·5 citations
06
[Submitted on 5 Mar 2024]
Implementation of the microscopic nuclear potential in the coupled channels calculations to study the fusion dynamics of Oxygen based reactions
N. Jain · M. Bhuyan · Raj Kumar
In the present work, we have incorporated the microscopic relativistic nuclear potential obtained from recently developed relativistic R3Y NN potential in the coupled channels code CCFULL to study the fusion dynamics. The R3Y NN-potential and the densities of interacting nuclei are obtained for the relativistic mean-field approach for the NL3 $^{*}$ parameter set. It is to be noted that the R3Y NN potential can be expressed in terms of masses of the mesons and their couplings by considering the meson degrees of freedom within the relativistic mean field, which has a form similar to the widely used M3Y potential. We focused on the fusion cross-sections for $O x y g e n$ -based reactions with targets from different mass regions of the periodic table i.e. $^{16}$ O + $^{24}$ Mg, $^{18}$ O + $^{24}$ Mg, $^{16}$ O + $^{148}$ Sm, $^{16}$ O + $^{176}$ Hf, $^{16}$ O + $^{176}$ Yb, $^{16}$ O + $^{182}$ W, and $^{16}$ O + $^{186}$ W. A comparison is also made with the ones calculated using the nuclear potential obtained from the traditional Woods-Saxon potential and the widely used M3Y NN potential within CCFULL. The coupled channel calculations are performed with shape and rotational degrees of freedom to examine the fusion enhancement at below-barrier energies. It is observed from the calculations that the fusion cross-sections obtained using R3Y NN potential with rotational degrees of freedom are found to be more consistent with the experimental data than those for the M3Y and Woods-Saxon potentials mainly at below barrier energies.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2403.02739 [pdf]
PRC(2024)·5 citations
07
[Submitted on 5 Mar 2024]
Relativistic mean-field study of alpha decay in superheavy isotopes with 100 \texorpdfstring{ $\leq$ Z $\leq$ }-120
Nishu Jain · M. Bhuyan · Raj Kumar
The $α$ -decay half-lives of superheavy nuclei with $100 \leq Z \leq 120$ are comprehensively analyzed using the axially deformed relativistic mean field (RMF) formalism for the NL3 $^{*}$ parameter set. We employ RMF binding energies to determine the $α$ -decay energies and make a comparison with both the available experimental data and the theoretical results obtained from the global nuclear mass model WS4. The four distinct formulae, specifically the modified scaling law Brown, modified Viola-Seaborg, Yibin {\it et al.} formula, and its modified form are used to calculate the decay half-lives and examine the numerical correlation between the half-life ( $T_{1/2}$ ) for each $α$ -decay energy. We notice that $T_{1/2}$ is significantly dependent on the decay formula in terms of isospin asymmetry and decay energy. We also noticed that modified scaling law Brown formula estimates of half-lives agreed comparatively better with the experiment as compared to others. Moreover, the present investigation provides significant information on the stability of the superheavy island considered for ongoing and/or future experiments.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2403.02748 [pdf]
Phys.Part.Nucl.Lett.(2024)·4 citations
08
[Submitted on 5 Mar 2024]
Kinetic temperature and radial flow velocity estimation using identified hadrons and light (anti-)nuclei produced in relativistic heavy-ion collisions at RHIC and LHC
Junaid Tariq🇮🇹 · M. U. Ashraf🇧🇪 · Grigory Nigmatkulov🇺🇸
We report the investigation of the kinetic freeze-out properties of identified hadrons ( $π^{\pm}$ , $K^{\pm}$ and $p (p ˉ)$ ) along with light (anti-)nuclei $d (d ˉ)$ , $t (t ˉ)$ and $^{3} H e$ in relativistic heavy-ion collisions at RHIC and LHC energies. A simultaneous fit is performed with the Blast-Wave (BW) model to the transverse momentum ({\ppt}) spectra of identified hadrons together with light (anti-)nuclei produced in $A u + A u$ collisions at {\sqrtsNN} = 7.7 -- 200 GeV at the RHIC and in $P b + P b$ collisions at $s_{_{NN}}$ = 2.76 TeV at the LHC. The energy and centrality dependence of freeze-out parameters, i.e., kinetic freeze-out temperature ( $T_{k in}$ ) and collective flow velocity $⟨ β ⟩$ has been studied. It is observed that light (anti-)nuclei also participate in the collective expansion of the medium created in the collision when included in a common fit with the light hadrons. We observe a marginal rise in $T_{k in}$ and a slight decrease in $⟨ β ⟩$ when compared to the values obtained from the fit to light hadrons. A similar $⟨ β ⟩$ and significantly larger $T_{k in}$ is observed when a fit is performed to only protons and light (anti-)nuclei. Both, $T_{k in}$ and $⟨ β ⟩$ show a weak energy dependence at most collision energies.
Comments:
11 pages, 6 figures, 4 Tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2403.02759 [pdf]
PRC(2024)·4 citations
09
[Submitted on 5 Mar 2024]
Examination of STAR fixed-target data on directed flow at $s_{N N} =$ 3 and 4.5 GeV
Yu. B. Ivanov🇷🇺 · M. Kozhevnikova🇷🇺
We present results of simulations of directed flow of various hadrons in Au+Au collisions at collision energies of $s_{N N} =$ 3 and 4.5 GeV. Simulations are performed within the model three-fluid dynamics (3FD) and the event simulator based on it (THESEUS). The results are compared with recent STAR data. The directed flows of various particles provide information on dynamics in various parts and at various stages of the colliding system depending on the particle. However, the information on the equation of state is not always directly accessible because of strong influence of the afterburner stage or insufficient equilibration of the matter. It is found that the crossover scenario gives the best overall description of the data. This crossover EoS is soft in the hadronic phase. The transition into QGP in Au+Au collisions occurs at collision energies between 3 and 4.5 GeV, at baryon densities $n_{B} \geq 4 n_{0}$ and temperatures $\approx 150$ MeV. In-medium effects in the directed flow of (anti)kaons are discussed.
Comments:
13 pages, 8 figures, title changed, discussion extended, one figure added. Version published in PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2403.02787 [pdf]
PRC(2024)·6 citations
10
[Submitted on 5 Mar 2024]
Translationally invariant shell model calculation of the quasielastic $(p, 2 p)$ process at intermediate relativistic energies
A.B. Larionov · Yu.N. Uzikov
Relativistic beams of heavy ions interacting with various nuclear targets allow to study a broad range of problems starting from nuclear equation of state to the traditional nuclear structure. Some questions which were impossible to answer heretofore -- can be addressed nowadays by using inverse kinematics. These includes the structure of short-lived nuclei and the precision study of exclusive channels with production of residual nuclei in certain quantum states. Theoretical understanding such processes is so far based on factorization models which combine the single-step amplitude of the reaction on a bound nucleon or nuclear cluster with a certain wave function of its relative motion with respect to the residual nucleus. The nuclear structure information is encoded in the spectroscopic amplitude, calculable within nuclear many-body theories. In this work, we use for this purpose the translationally-invariant shell model with configuration mixing and demonstrate that it successfully reproduces the single-differential and integrated cross sections of the quasielastic proton knockout, $^{12} \mbox C (p, 2 p)^{11} \mbox B$ , with outgoing $^{11}$ B in the ground state and low-lying excited states measured at GSI at 400 MeV/nucleon.
Comments:
26 pages, 6 figures, model description extended, version accepted in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2403.02812 [pdf]
PRC(2024)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE