Nuclear Theory·nucl-th

Friday·March 1, 2024

15 papers—8 primary·7 cross-listed

01
Generator coordinate method with proton--neutron pairing fluctuations and magnetic properties of $N = Z$ odd--odd nuclei
K. Uzawa · N. Hinohara · T. Nakatsukasa
Pairing correlations play an important role in a variety of nuclear phenomena. However, a quantitative understanding of proton--neutron $(p n)$ pairing, especially isoscalar $p n$ pairing $(S = 1, T = 0)$ remains elusive. To clarify the property of $p n$ pairing, we investigate the roles of $p n$ pairing in the $M 1$ transition of $N = Z$ odd--odd nuclei. We develop a theoretical model based on the generator coordinate method (GCM) in which the isoscalar and isovector $p n$ -pair amplitudes are used as the generator coordinates. Using the particle and the angular-momentum projections, the $p n$ -pair GCM well reproduces the $M 1$ transition of odd--odd nuclei for the exactly solvable SO(8) model. We apply the method to $N = Z$ odd--odd nuclei and find that the experimental values of $B (M 1)$ are well reproduced. We also study the sensitivity of $B (M 1)$ to the strength of the isoscalar pairing interaction.
nucl-thPTEP(2024)·6 citations
02
Observational Probes of the Neutron Star Equation of State with Hyperons, Bosonic Dark Matter, and Quark Matter
Mahboubeh Shahrbaf🇵🇱 · Davood Rafiei Karkevandi🇵🇱 · Alexander Ayriyan🇵🇱 · Stefan Typel🇩🇪
Context. The presence of dark matter in neutron stars is of growing interest due to its potential impact on the structure and observable properties of these objects. Among the various candidates, the hypothetical sexaquark has emerged as a promising bosonic dark matter particle, potentially forming under extreme conditions in neutron star cores. Aims. We investigate whether a hybrid neutron star model that includes hyperons, bosonic dark matter (in the form of sexaquarks), and deconfined quark matter can satisfy all current observational constraints. We particularly focus on identifying the range of sexaquark masses consistent with mass-radius measurements and the tidal deformability limit. Methods. We used the DD2Y-T model for the hadronic phase, which includes hyperons, and a nonlocal Nambu-Jona-Lasinio model for the deconfined quark phase. The phase transition was modeled as a smooth crossover using the replacement interpolation construction method. Sexaquark-baryon interactions were introduced via an effective mass shift representing repulsion. We incorporated the full set of current observational data, including NICER measurements of PSRs J0437-4715 and newly published J0614-3329 data, and performed a Bayesian analysis to constrain the sexaquark mass. Results. Our results show that the presence of the sexaquark softens the equation of state, enabling the hybrid model to satisfy both the radius and tidal deformability constraints around the canonical 1.4 M_\odot neutron stars. We find that hybrid EOSs with a sexaquark mass around 1900 MeV are in agreement with all available constraints, including those from HESS J1731-347 and PSR J0952-0607, which represent the lowest and highest mass neutron stars observed to date. The Bayesian analysis favors a sexaquark mass range of 1885-1935 MeV, supporting the potential relevance of this exotic particle in neutron star interiors.
nucl-thhep-phAstron.Astrophys.(2026)·17 citations
03
Spectroscopy of N=50 isotones with the valence-space density matrix renormalization group
A. Tichai · K. Kapás · T. Miyagi · M. A. Werner · Ö. Legeza · A. Schwenk · G. Zarand
The recently proposed combination of the valence-space in-medium similarity renormalization group (VS-IMSRG) with the density matrix renormalization group (DMRG) offers a scalable and flexible many-body approach for strongly correlated open-shell nuclei. We use the VS-DMRG to investigate the low-lying spectroscopy of N=50 isotones, which are characteristic for their transition between single-particle and collective excitations. We also study electromagnetic transitions and show the advantage of the VS-DMRG to capture the underlying physics more efficiently, with significantly improved convergence compared to state-of-the-art shell-model truncations. Combined with an analysis of quantum information measures, this further establishes the VS-DMRG as a valuable method for ab initio calculations of nuclei.
nucl-thcond-mat.str-elPLB(2024)·24 citations
04
A direct probe of $Λ$ potential in nuclear medium
Gao-Chan Yong🇨🇳
Using the Liège intranuclear-cascade model together with the ablation model ABLA, an investigation is conducted into the effects of $Λ$ potential in $Λ$ -nucleus and $Λ$ -hypernucleus-nucleus collisions across various beam energies. The findings show that the angle and transverse-momentum distributions of scattered $Λ$ hyperon, the scattering cross section of the $Λ$ hyperon in $Λ$ -nucleus collisions as well as the rapidity distribution of $Λ$ hyperon in $Λ$ -hypernucleus-nucleus collisions are significantly influenced by the strength of the $Λ$ potential in these scattering reactions across various beam energies. These demonstrations, unhindered by the uncertainties of $Λ$ and hypernuclei productions in nuclear medium, allow for a direct investigation of the $Λ$ potential, especially its momentum dependence. The criticality of probing the $Λ$ potential is closely associated with the resolution of the "hyperon puzzle" in neutron stars.
nucl-thhep-exhep-phnucl-exPLB(2024)·4 citations
05
Hadron-quark phase transition in the neutron star with vector MIT bag model and Korea-IBS-Daegu-SKKU functional
Debashree Sen🇰🇷 · Hana Gil🇰🇷 · Chang Ho Hyun🇰🇷
Employing the Korea-IBS-Daegu-SKKU (KIDS) density functional for the hadron phase and the MIT bag model with vector (vBag) model for the quark phase, we obtain hadron-quark phase transition in neutron stars considering Maxwell construction. The structural properties of the resultant hybrid stars are computed for three different values of bag constant ( $B$ ) in the range $B^{1/4} =$ (145 $-$ 160 MeV). We study the effects of symmetry energy ( $J$ ) on the hybrid star properties with the different KIDS model and found that $J$ has important influence not only on the transition properties like the transition mass, transition radius and jump in density due to phase transition, but also on the stability of the hybrid stars. The vector repulsion of the quark phase via the parameter $G_{V}$ has profound influence in obtaining reasonable hybrid star configurations, consistent with the recent astrophysical constraints on the structural properties of compact stars. Within the aforesaid range of $B$ , the value of $G_{V}$ is constrained to be 0.3 $≲ G_{V} ≲$ 0.4 in order to obtain reasonable hybrid star configurations.
nucl-thhep-phFront.Astron.Space Sci.(2024)·6 citations
06
Investigation of the determination of nuclear deformation using high-energy heavy-ion scattering
Shin Watanabe · Takenori Furumoto · Wataru Horiuchi · Tadahiro Suhara · Yasutaka Taniguchi
Background: Nuclear deformation provides a crucial characteristic of nuclear structure. Conventionally, the quadrupole deformation length of a nucleus, $δ_{2}$ , has often been determined based on a macroscopic model through a deformed nuclear potential with the deformation length $δ_{2}^{(pot)}$ , which is determined to reproduce the nuclear scattering data. This approach assumes $δ_{2} = δ_{2}^{(pot)}$ although there is no theoretical foundation. Purpose: We clarify the relationship between $δ_{2}$ and $δ_{2}^{(pot)}$ for high-energy heavy-ion scattering systematically to evaluate the validity of the conventional approach to determine the nuclear deformation. Method: The deformation lengths for the $^{12}$ C inelastic scattering by $^{12}$ C, $^{16}$ O, $^{40}$ Ca, and $^{208}$ Pb targets at $E / A$ = 50--400 MeV are examined. First, we perform microscopic coupled-channel (CC) calculations to relate $δ_{2}$ of the deformed density into the inelastic scattering cross section. Second, we use the deformed potential model to determine $δ_{2}^{(pot)}$ so as to reproduce the microscopic CC result. We then compare $δ_{2}^{(pot)}$ with $δ_{2}$ . Results: We find that $δ_{2}^{(pot)}$ is about 20--40 \% smaller than presumed $δ_{2}$ , showing strong energy and target dependence. Further analysis, which considers higher-order deformation effects beyond the derivative model, reveals that $δ_{2}^{(pot)}$ is still about 15--35 \% smaller than $δ_{2}$ . Conclusion: Our results suggest that one needs to be careful when the deformed potential model for the high-energy heavy-ion scattering is used to extract the nuclear deformation. The conventional approach may underestimate the deformation length $δ_{2}$ systematically.
nucl-thPRC(2024)·0 citations
07
Symmetry Energy from Two-Nucleon Separation Energies of Pb and Ca Isotopes
Myeong-Hwan Mun · Eunja Ha · H. Sagawa · Gianluca Colò · Myung-Ki Cheoun
We investigate the symmetry energy in relation with the two-proton and two-neutron separation energies using different nuclear mass data. For this aim, we exploit the deformed relativistic Hartree-Bogoliubov theory in the continuum (DRHBc), FRDM2012 and AME2020 data. First, we study the two-proton and two-neutron separation energies in Pb and Ca isotopes by subtracting the contribution of Coulomb energy. They show a strong correlation with neutron number as well as with the neutron skin thickness. By taking the relative difference of both separation energies, we derive the symmetry energy from Ca and Pb isotopes. Since the nuclear surface contributes to the symmetry energy, we deduce the volume symmetry energy by subtracting the surface contribution using several mass models. The obtained symmetry energy coefficient, $a_{sy m}$ , is 20.0 $\sim$ 22.7 MeV for Pb isotopes and 18.7 $\sim$ 19.3 MeV for Ca isotopes from the DRHBc mass table data, while the results from other mass tables are 19.6 $\sim$ 22.1 (20.7 $\sim$ 22.3) MeV for Pb isotopes and 18.9 $\sim$ 19.0 (19.6 $\sim$ 19.7) MeV for Ca isotopes from AME2020 (FRDM2012) data. The volume contribution to the asymmetry coefficient, $a_{sy m}^{v}$ , which depends on the ratio of the surface to the volume energy coefficients, $a_{s} / a_{v}$ , is also provided for each mass model. Since the ratio $a_{s} / a_{v}$ is neither determined by nuclear theory, nor by experimental data, we have investigated $a_{sy m}^{v}$ by using the ratio $a_{s} / a_{v}$ as a free parameter, and have obtained $a_{sy m}^{v} =$ 27.0 MeV, almost irrespective of nuclear model and isotopic chain, with the ratio $a_{s} / a_{v}$ constrained as $a_{s} / a_{v} = 1.10 \sim 1.13$ .
nucl-thPRC(2024)·9 citations
08
Infinite Order Hydrodynamics: An Analytical Example
Lorenzo Gavassino🇺🇸
We construct a kinetic model for matter-radiation interactions whose hydrodynamic gradient expansion can be computed analytically up to infinite order in derivatives, in the fully nonlinear regime, and for arbitrary flows. The frequency dependence of the opacity of matter is chosen to mimic the relaxation time of a self-interacting scalar field. In this way, the transient sector simulates that of a realistic quantum field theory. The gradient series is found to diverge for most flows, in agreement with previous findings. We identify, for the model at hand, the mechanism at the origin of the divergence, and we provide a successful regularization scheme. Additionally, we propose a universal qualitative framework for predicting the breakdown of the gradient expansion of an arbitrary microscopic system undergoing a given flow. This framework correctly recovers all previously known instances of gradient expansion divergence. As a new prediction, we show that the gradient expansion diverges when the energy-dependent mean free path is unbounded above.
nucl-thastro-ph.HEgr-qchep-ph+1PRL(2024)·12 citations
09
Analytic solutions for the linearized first-order magnetohydrodynamics and implications for causality and stability
Zhe Fang🇨🇳 · Koichi Hattori🇨🇳 · Jin Hu🇨🇳
We address the linear-mode analysis performed near an equilibrium configuration in the fluid rest frame with a dynamical magnetic field perturbed on a constant configuration. We develop a simple and general algorithm for an analytic solution search that works on an order-by-order basis in the derivative expansion. This method can be applied to general sets of hydrodynamic equations. Applying our method to the first-order relativistic magnetohydrodynamics, we demonstrate that the method finds a complete set of solutions. We obtain two sets of analytic solutions for the four and two coupled modes with seven dissipative transport coefficients. The former set has been missing in the literature for a long time due to the difficulties originating from coupled degrees of freedom and strong anisotropy provided by a magnetic field. The newly developed method resolves these difficulties. We also find that the small-momentum expansions of the solutions break down when the momentum direction is nearly perpendicular to an equilibrium magnetic field due to the presence of another small quantity, that is, a trigonometric function representing the anisotropy. We elaborate on the angle dependence of the solutions and provide alternative series representations that work near the right angle. This identifies the origin of a discrepancy found in recent works. Finally, we discuss the issues of causality and stability based on our analytic solutions and recent developments in the literature.
↳ physics.plasm-phastro-ph.HEgr-qchep-ph+1PRD(2024)·15 citations
10
Exploring the distribution and impact of bosonic dark matter in neutron stars
Davood Rafiei Karkevandi🇮🇷 · Mahboubeh Shahrbaf🇵🇱 · Soroush Shakeri🇮🇷 · Stefan Typel🇩🇪
The presence of dark matter (DM) within neutron stars (NSs) can be introduced by different accumulation scenarios in which DM and baryonic matter (BM) may interact only through the gravitational force. In this work, we consider asymmetric self-interacting bosonic DM which can reside as a dense core inside the NS or form an extended halo around it. It is seen that depending on the boson mass ( $m_{χ}$ ), self-coupling constant ( $λ$ ) and DM fraction ( $F_{χ}$ ), the maximum mass, radius and tidal deformability of NSs with DM admixture will be altered significantly. The impact of DM causes some modifications in the observable features induced solely by the BM component. Here, we focus on the widely used nuclear matter equation of state (EoS) called DD2 for describing NS matter. We show that by involving DM in NSs, the corresponding observational parameters will be changed to be consistent with the latest multi-messenger observations of NSs. It is seen that for $m_{χ} ≳ 200$ MeV and $λ ≲ 2 π$ , DM admixed NSs with $4% ≲ F_{χ} ≲ 20%$ are consistent with the maximum mass and tidal deformability constraints.
↳ astro-ph.HEnucl-thParticles(2024)·41 citations
11
Relativistic fluctuations in stochastic fluid dynamics
Xin An🇵🇱 · Gokce Basar🇺🇸 · Mikhail Stephanov🇺🇸 · Ho-Ung Yee🇺🇸
The state-of-the-art theoretical formalism for a covariant description of non-Gaussian fluctuation dynamics in relativistic fluids is discussed.
↳ hep-thcond-mat.stat-mechhep-phnucl-thEPJ Web Conf.(2024)·1 citation
12
QCD at Finite Temperature and Density -- Equation of State
Jamie M. Karthein🇺🇸
As an important set of thermodynamic quantities, knowledge of the equation of state over a broad range of temperatures and chemical potentials in the QCD phase diagram is crucial for our understanding of strongly-interacting matter. There is a good understanding from first-principles results in lattice QCD, perturbative QCD and chiral effective field theory about the equation of state. However, these approaches are valid in different regimes of the phase diagram, and therefore, a method of providing an equation of state that covers a full range of the phase diagram involves matching together these results with appropriate models in order to fill in the gaps between these regions. Furthermore, with such equations of state, important questions about QCD phase structure can begin to be addressed, such as whether there is a critical point in the QCD phase diagram. In this contribution to the proceedings, equations of state from first-principles and effective theories will be discussed in order to understand how QCD thermodynamics is affected by the presence of a critical point.
↳ hep-phnucl-thEPJ Web Conf.(2024)·1 citation
13
B-mesons as essential probes of hot QCD matter
Vinod Chandra🇮🇳 · Santosh K. Das🇮🇳
This article elucidates the pivotal role of b-mesons and bottomonium states in exploring the existence and properties of hot QCD matter (commonly known as quark-gluon-plasma (QGP) produced within the crucible heavy-ion collision experiments). Owing to the complex and confounding nature of strong interaction force the direct detection of probing the hot QCD matter is not feasible. In light of this, investigating the dynamics of b-quarks and anti-quarks within the hot QCD medium emerges as an invaluable indirect probe. The impact of b-quarks and the mesons spans a spectrum of interesting domains regarding the physics of QCD at finite temperature, encompassing the QCD phase transition, color screening, quarkonia dissociation, heavy quark energy loss and collective flow, anisotropic aspects, and strongly coupled nature of hot QCD medium. These aspects underscore the indispensable nature of B-mesons in the quest to create and explore the complex nature of strong interaction force through the QGP/hot QCD matter. In this context, we mainly focus on works related to transport studies of b-mesons in hot QCD medium, lattice QCD, and effective field theory studies on bottomonium states, and finally, open quantum system frameworks to quarkonia to explore the properties of hot QCD medium in relativistic heavy-ion collision experiments.
↳ hep-phnucl-thEur.Phys.J.ST(2024)·7 citations
14
Nuclear medium meson structures from the Schwinger proper-time Nambu--Jona-Lasinio model
Geoffry Gifari🇮🇩 · Parada T. P. Hutauruk🇰🇷 · Terry Mart🇮🇩
In this paper, we report the results of our study on the nuclear medium modifications of the meson electromagnetic form factors in the framework of the Nambu--Jona-Lasinio (NJL) model with the help of the Schwinger proper-time regularization scheme to tame the loop divergence and simulate the effect of QCD confinement. In our current approach, the meson structure and nuclear medium are constructed in the same NJL model at the quark level. We examine the free-space and in-medium charge radii of kaon and pion, the spacelike elastic electromagnetic form factors of kaon and pion, and their quark-sector form factors, which reflect their internal structures. By comparing our result to experimental data, we found that the free-space elastic electromagnetic form factors of the mesons are consistent with the data, while the in-medium elastic electromagnetic form factors of the mesons are found to decrease as the nuclear matter density increases, leading to a rise of meson charge radius, which is consistent with the prediction of other theoretical calculations. We also predict the axial nucleon coupling constant $g_{A}$ in nuclear medium computed via the Goldberger-Treiman relation (GTR), which is crucial for searching the neutrinoless double beta decay ( $0 ν β β$ ).
↳ hep-phnucl-thPRD(2024)·17 citations
15
Revisiting $O (N)$ $σ$ model at unphysical pion masses and high temperatures
Yuan-Lin Lyu🇨🇳 · Qu-Zhi Li🇨🇳 · Zhiguang Xiao🇨🇳 · Han-Qing Zheng🇨🇳
Roy-equation analyses on lattice data of $π π$ scattering phase shifts at $m_{π} = 391$ MeV reveals that the lowest $f_{0}$ meson becomes a bound state under this condition. In addition, there is a pair of complex poles below threshold generated by crossing symmetry [X.-H. Cao et al., Phys. Rev. D 108, 034009 (2023)]. We use the $N / D$ method to partially recover crossing symmetry of the $O (N)$ $σ$ model amplitude at leading order of $1/ N$ expansion, and qualitatively reproduce the pole structure and pole trajectories with varying pion masses as revealed by Roy-equation analyses. The $σ$ pole trajectory with varying temperature is also discussed and found to be similar to its properties when varying $m_{π}$ . As the temperature increases, the complex $σ$ poles firstly move from the second Riemann sheet to the real axis becoming two virtual state poles, and then one virtual state pole moves to the first sheet turning into a bound state pole and finally tends to the pion pole position at high temperature which is as expected from the chiral symmetry restoration. Our results provide further evidences that the lowest $f_{0}$ state extracted from experiments and lattice data plays the role of $σ$ meson in the spontaneous breaking of chiral symmetry. Finally, we also briefly discuss the problems of the effective potential in the situation when $m_{π}$ and temperature get large.
↳ hep-phhep-lathep-thnucl-thPRD(2024)·7 citations

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