Nuclear Theory·nucl-th

Tuesday·October 15, 2024

16 papers—8 primary·8 cross-listed

01
Investigating the Bulk Properties of Charged Particles in Different $η$ Bins Using a Modified Tsallis Model
Haifa I. Alrebdi🇸🇦 · Muhammad Ajaz🇵🇰 · Murad Badshah🇵🇰 · Muhammad Waqas🇨🇳 · Nourah A.M. Alsaif🇸🇦
This paper presents a comprehensive analysis of the double-differential $p_{T}$ distributions of charged particles in twelve distinct pseudorapidity regions of equal width in $pp$ collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV. Utilizing the modified Tsallis function with mean transverse flow velocity, our study demonstrates a very good agreement between experimental data and the model employed. The fit quality is consistently high across all $p_{T}$ ranges, as assessed by Data/Fit panels accompanying each plot. Extracted parameters, including kinetic freeze-out temperature ( $T_{0}$ ), transverse flow velocity ( $β_{T}$ ), non-extensivity parameter ( $q$ ) and mean transverse momentum $⟨ p_{T} ⟩$ dependencies are shown on pseudorapidity ( $η$ ) and collision energy ( $s$ ). $T_{0}$ , $β_{T}$ and $⟨ p_{T} ⟩$ exhibit a decreasing trend with increasing $η$ due to lower in energy transfer along high $η$ regions, while they show a heightened sensitivity to $s$ . $q$ increases with $η$ , indicating a closer thermal equilibrium in mid- $η$ particles. The paper also explores correlations among these parameters, emphasizing relationships between $T_{0}$ , $β_{T}$ , $q$ and $⟨ p_{T} ⟩$ . Our study provides valuable insights into the thermal and dynamic characteristics of high-energy proton-proton collisions, contributing to the broader understanding of the bulk properties of nuclear matter produced in these interactions.
hep-phnucl-th0 citations
02
Learning from knockout reactions using a dispersive optical model
M.C. Atkinson · W.H. Dickhoff
We present the empirical dispersive optical model (DOM) as applied to direct nuclear reactions. The DOM links both scattering and bound-state experimental data through a dispersion relation which allows for fully-consistent, data-informed predictions for nuclei where such data exists. In particular, we review investigations of the electron-induced proton knockout reaction from both $^{40}$ Ca and $^{48}$ Ca in a distorted-wave impulse approximation (DWIA) utilizing the DOM for a fully-consistent description. Viewing these reactions through the lens of the DOM allows us to connect the documented quenching of spectroscopic factors with increased high-momentum proton content in neutron-rich nuclei. A similar DOM-DWIA description of the proton-induced knockout from $^{40}$ Ca, however, does not currently fit in the consistent story of its electron-induced counterpart. With the main difference in the proton-induced case being the use of an effective proton-proton interaction, we suggest that a more sophisticated in-medium interaction would lead to consistent results.
nucl-thFront.in Phys.(2024)·1 citation
03
Theoretical study on $Λ α$ and $Ξ α$ correlation functions
Asanosuke Jinno🇯🇵 · Yuki Kamiya🇩🇪 · Tetsuo Hyodo🇯🇵 · Akira Ohnishi🇯🇵
We examine the $Λ$ - $^{4} He$ ( $α$ ) and $Ξ α$ momentum correlation in high-energy collisions to further elucidate the properties of the hyperon-nucleon interactions. For the $Λ α$ system, we compare $Λ α$ potential models with different strengths at short range. We find that the difference among the models is visible in the momentum correlation from a small-size source. This indicates that the $Λ α$ momentum correlation can constrain the property of the $Λ N$ interaction at short range, which plays an essential role in dense nuclear matter. For the $Ξ α$ system, we employ the folding $Ξ α$ potential based on the lattice QCD $Ξ N$ interactions. The $Ξ α$ potential supports a Coulomb assisted bound state of $_{Ξ}^{5} H$ in the $Ξ^{-} α$ channel, while the $Ξ^{0} α$ channel is unbound. To examine the sensitivity of the correlation function to the nature of the $Ξ α$ potential, we vary the potential strength simulating stronger and weaker interactions. The result of the correlation function clearly reflects the bound state nature in the $Ξ^{-} α$ correlation.
nucl-thJ.Subatomic Part.Cosmol.(2024)·2 citations
04
Fission fragment distributions within time-dependent density functional theory
Yun Huang · Xiang-Xiang Sun · Lu Guo
A notable issue, the proper description of mass and charge distributions of fission fragments within nonadiabatic descriptions of fission dynamics, is investigated by performing double particle number projection on the outcomes of time-dependent Hartree-Fock (TDHF) simulation. The induced fission process of the benchmark nucleus 240Pu is studied. In the three-dimensional Cartesian coordinate without any symmetry restrictions, we get the static fission pathway from the two-dimensional potential energy surface, and then the fission dynamics from saddle to scission point are obtained using TDHF. We show that the charge numbers of primary heavy fragments from TDHF simulation strongly depend on the deformations of initial configurations via the two asymmetric fission channels, which can be distinguished according to the dynamical fission trajectories. The charge distribution of fission fragments is well reproduced using the double particle number projection technique. After applying the Gaussian kernel estimation based on the distribution from the double particle number projection technique, the mass distribution is also consistent with the experimental results. Besides, the results of the total kinetic energy of fission fragments are reasonably consistent with the experiments.
nucl-thEPJA(2024)·7 citations
05
Role of the tensor force in induced fission of 240Pu
Yun Huang · Xiang-Xiang Sun · Lu Guo
Results: We find that the tensor force affects the height of fission barriers and the double-humped structure of fission path of 240Pu. On the PES, the fission valley becomes larger in the (Q20, Q30) plane, and the triaxial deformation is suppressed around the outer barrier after considering the tensor force. Incorporating the tensor force into the dynamical process enhances the difference in shape evolution between two asymmetric channels. More interestingly, the charge distribution from TDHF with double PNP calculations shows a strong odd-even effect after including the tensor force. In addition, the total mass and charge distributions of fission fragments show a slight shift towards larger asymmetry and are more consistent with the experiments when tensor components are included. We also find that the tensor force enhances energy gaps of the deformed shells for heavy fragments. Moreover, the TKEs of fragments are in accord with the experiments, and after incorporating the tensor force, we observe a higher concentration of the calculated TKEs for heavy fragments at Z = 52 and Z = 56. Conclusions: The tensor force plays a role in both static and dynamical processes in nuclear fission, improving the accuracy of theoretical descriptions within the current framework. Our calculations have shown that the fission-barrier height with SLy5t is closer to the empirical value than that of SLy5. Additionally, the inclusion of the tensor force not only manifests the odd-even effect in charge distribution but also improves the description of total mass and charge distributions.
nucl-thnucl-exPRC(2024)·8 citations
06
On Two Nucleons Near Unitarity with Perturbative Pions
Yu Ping Teng (U. of Wisconsin-Madison and George Washington University)🇺🇸 · Harald W. Griesshammer (George Washington U.)🇺🇸
We explore the impact of perturbative pions on the Unitarity Expansion in the two-nucleon S-waves of Chiral Effective Field Theory at next-to-next-to leading order. Pion exchange explicitly breaks the nontrivial fixed point's universality and invariance under conformal and Wigner- $\SU (4)$ spin-isospin transformations. This Chiral Effective Field Theory applies tothe Unitarity Window (45deg<delta(k)<135deg, $k \approx m_{π}$ ) most relevant for low-energy nuclear systems. Its only LO scale is the scattering momentum; NLO adds only scattering length, effective range and non-iterated one-pion exchange (OPE); and N2LO only once-iterated OPE. Agreement in the 1S0 channel is very good. Apparent large discrepancies in the 3S1 channel at k>100MeV are remedied by taking only the central part of the pion's N2LO contribution. In contradistinction to the tensor part, it is invariant under Wigner-SU(4)symmetry and hence identical in 1S0 and 3S1. NLO pions are Wigner-invariant. Both channels describe PWAs and pole parameters well within mutually consistent quantitative theory uncertainty estimates. Pionic effects are small, even for k>mpi. Empirically determined breakdown scales agree well with $Λ_{N N} = \frac{16 π f _{π}^{2}}{g _{A}^{2} M} = 300$ MeV where iterated OPE is not suppressed. We therefore conjecture: The footprint of both scale invariance and Wigner-symmetry in the Unitarity Expansion shows persistence,i.e. both dominate even for k=mpi and are more relevant than chiral symmetry,so that the tensor/Wigner-SU(4) symmetry-breaking part of OPE does not enter before N3LO. We also discuss the potential relevance of entanglement power and possible resolution of a conflict with the strength of the tensor interaction in the large-Nc expansion.
nucl-thhep-phEPJA(2025)·6 citations
07
Universal laws for nuclear contacts
Tongqi Liang · Dong Bai · Zhongzhou Ren
The nuclear contact characterizes the nucleon-nucleon pairs in close proximity and serves as an important tool for studying the short-range correlations (SRCs) within atomic nuclei. While they have been extracted for selected nuclei, the investigation of their behavior across the nuclear chart remains limited. Very recently, Yankovich, Pazy, and Barnea have proposed a set of universal laws (YPB laws) to describe the correlation between nuclear contacts and nuclear radii and tested their laws for a small number of nuclei by using the Woods-Saxon mean-field model~[R.\ Yankovich, E.\ Pazy, and N.\ Barnea, arXiv:2407.15068 (2021)]. In this Letter, we extend their study to a majority part of the chart of nuclides within the framework of the Skyrme Hartree-Fock-Bogolyubov model, which incorporates several essential beyond-mean-field features and offers a more accurate description of the bulk properties of atomic nuclei. Our results suggest that the YPB laws hold as a good approximation for different nuclear mass regions, with minor deviations attributed to, e.g., isospin-breaking effects. Our work lays a firm foundation for future applications of the YPB laws in finite nuclei and provides new evidence for the long-range nature of the relative abundance of short-range pairs.
nucl-thPLB(2025)·4 citations
08
Relaxation of particle-hole type excitation in a Fermi system within the diffusion approximation of kinetic theory for the case of constant diffusion and drift coefficients
Sergiy V. Lukyanov
The time evolution of the distribution function for a particle-hole excitation in a Fermi system was calculated using the direct numerical solution of a nonlinear diffusion equation in momentum space. A phenomenological expression for calculating the relaxation time of such an excitation to its equilibrium value has been proposed. It is shown that the relaxation time is dependent on both the excitation energy and the mass number.
nucl-thActa Phys.Polon.B(2025)·2 citations

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first authorsco-authorsvia INSPIRE