Nuclear Theory·nucl-th

Thu·Nov 23, 2023Thursday·November 23, 2023

9 papers—4 primary·5 cross-listed

01
Understanding the Effect of Chiral NN Parametrization on Nuclear Shapes From an Ab Initio Perspective
Kevin S. Becker🇺🇸 · Kristina D. Launey🇺🇸 · Andreas Ekström🇸🇪 · Grigor H. Sargsyan🇺🇸 · Darin C. Mumma🇺🇸 · Tomáš Dytrych🇺🇸 · Daniel Langr🇨🇿 · Jerry P. Draayer🇺🇸
The ab initio symmetry-adapted no-core shell model naturally describes nuclear deformation and collectivity, and is therefore well-suited to studying the dynamics and coexistence of shapes in atomic nuclei. For the first time, we analyze how these features in low-lying states of 6Li and 12C are impacted by the underlying realistic nucleon-nucleon interaction. We find that the interaction parametrization has a notable but limited effect on collective shapes in the lowest 6Li and 12C states, while collective structures in the excited 2+ state of 12C are significantly more sensitive to the interaction parameters and exhibits emergent shape coexistence.
nucl-thEPJ Web Conf.(2025)·1 citation
02
Strong Gravity Extruding Peaks in Speed of Sound Profiles of Massive Neutron Stars
Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸
The speed of sound squared (SSS) $s^{2}$ in massive neutron stars (NSs) characterizes not only the stiffness of supradense neutron-rich matter within but also equivalently properties of the curved geometry due to the strong-field gravity and matter-geometry coupling. A peaked density or radius profile of $s^{2}$ has been predicted for massive NSs using various NS Equation of State (EOS) models. However, the nature, cause, location and size of the peak in $s^{2}$ profiles are still very EOS model dependent. In this work, we investigate systematically $s^{2}$ profiles in massive NSs in a new approach that is independent of the nuclear EOS model and without any presumption about the NS structure and/or composition. In terms of the small quantities (reduced radius, the energy density and pressure scaled by their central values), we perform double-element perturbative expansions in solving perturbatively the scaled Tolman--Oppenheimer--Volkoff (TOV) equations and analyzing $s^{2}$ profiles from the Newtonian limit to the general relativistic (GR) case. The GR term in the TOV equations plays a twofold role: it compresses NS matter and modifies the pressure/energy density ratio from small values in Newtonian stars showing no $s^{2}$ peak to large ones for massive NSs possessing a peak in their $s^{2}$ profiles, and eventually takes away the peak in extremely compact/massive NSs approaching the causality limit. {In particular, the peaked behavior in $s^{2}$ is expected to emerge near the center of massive NSs like PSR J0740+6620, while a sharp phase transition is unlikely to occur there.} These features revealed from our analyses are universal as they are intrinsic properties of the GR stellar structure equations independent of the still very uncertain EOS of supradense neutron-rich matter in NSs.
nucl-thastro-ph.HEastro-ph.SRgr-qc+1PRD(2024)·14 citations
03
Curvature of the energy per particle in neutron stars
Michał Marczenko🇵🇱 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱
Neutron stars (NSs) serve as laboratories for probing strongly interacting matter at the most extreme densities. Their inner cores are expected to be dense enough to host deconfined quark matter. Utilizing state-of-the-art theoretical and multi-messenger constraints, we statistically determine the bulk properties of dense NS matter. We show that the speed of sound can be expressed in terms of the slope and curvature of the energy per particle. We demonstrate that the restoration of conformal symmetry requires changing the sign of the curvature of the bulk energy per particle as a function of energy density. Furthermore, we find that such a sign change is closely related to the peak in the speed of sound. We argue that the curvature of the energy per particle may serve as an approximate order parameter that signifies the onset of strongly coupled conformal matter in the NS core.
nucl-thastro-ph.HEhep-phPRD(2024)·21 citations
04
Nuclear Structure Effects on Hyperfine Splittings in Ordinary and Muonic Deuterium
Chen Ji🇨🇳 · Xiang Zhang🇨🇳 · Lucas Platter🇺🇸
Precision spectroscopy of hyperfine splitting (HFS) is a crucial tool for investigating the structure of nuclei and testing quantum electrodynamics (QED). However, accurate theoretical predictions are hindered by two-photon exchange (TPE) effects. We propose a novel formalism that accounts for nuclear excitations and recoil in TPE, providing a model-independent description of TPE effects on HFS in light ordinary and muonic atoms. Combining our formalism with pionless effective field theory at next-to-next-to-leading order, the predicted TPE effects on HFS are 41.2(2.6) kHz and 0.116(9) meV for the 1S state in deuterium and the 2S state in muonic deuterium. These results are within 1.4-1.7 standard deviation from recent measurements and highlight the importance of nuclear structure effects on HFS and indicate the value of more precise measurements in future experiments.
nucl-thphysics.atom-phPRL(2024)·7 citations
05
Numerical modelling of bulk viscosity in neutron stars
Michail Chabanov🇩🇪 · Luciano Rezzolla🇩🇪
The early post-merger phase of a binary neutron-star coalescence is shaped by characteristic rotational velocities as well as violent density oscillations and offers the possibility to constrain the properties of neutron star matter by observing the gravitational wave emission. One possibility to do so is the investigation of gravitational wave damping through the bulk viscosity which originates from violations of weak chemical equilibrium. Motivated by these prospects, we present a comprehensive report about the implementation of the self-consistent and second-order formulation of the equations of relativistic hydrodynamics for dissipative fluids proposed by Müller, Israel and Stewart. Furthermore, we report on the results of two test problems, namely the viscous damping of linear density oscillations of isolated nonrotating neutron stars and the viscous migration test, both of which confirm our implementation and can be used for future code tests. Finally, we present fully general-relativistic simulations of viscous binary neutron-star mergers. We explore the structural and thermal properties of binary neutron-star mergers with a constant bulk-viscosity prescription and investigate the impact of bulk viscosity on dynamical mass ejection. We find that inverse Reynolds numbers $\sim 1%$ can be achieved for the highest employed viscosity thereby suppressing the dynamically ejected mass by a factor of $\sim 5$ compared to the inviscid case.
↳ gr-qcastro-ph.HEnucl-thPRD(2025)·44 citations
06
Magnetic field dependence of the neutral pion longitudinal screening mass in the linear sigma model with quarks
Alejandro Ayala🇲🇽 · Ricardo L. S. Farias🇧🇷 · L. A. Hernández🇲🇽 · Ana Julia Mizher🇧🇷 · Javier Rendón🇲🇽 · Cristian Villavicencio🇨🇱 · R. Zamora🇨🇱
We use the linear sigma model with quarks to study the magnetic-field-induced modifications on the longitudinal screening mass for the neutral pion at one-loop level. The effects of the magnetic field are introduced into the self-energy, which contains the contributions from all the model particles. We find that, to obtain a reasonable description for the behavior with the field strength, we need to account for the magnetic field dependence of the particle masses. We also find that the couplings need to decrease fast enough with the field strength to then reach constant and smaller values as compared to their vacuum ones. The results illustrate the need to treat the magnetic corrections to the particle masses and couplings in a self-consistent manner, accounting for the backreaction of the field effects for the magnetic field dependence of the rest of the particle species and couplings in the model.
↳ hep-phhep-latnucl-thPRD(2024)·15 citations
07
Analysis of the data for $γ p \to f_{1} (1285) p$ photoproduction
Ai-Chao Wang🇨🇳 · Neng-Chang Wei🇨🇳 · Fei Huang🇨🇳
The photoproduction of $f_{1} (1285)$ meson off proton is investigated within an effective Lagrangian approach. The $t$ -channel $ρ$ - and $ω$ -exchange diagrams, $u$ -channel nucleon-exchange diagram, generalized contact term, and $s$ -channel pole diagrams of nucleon and a minimal number of nucleon resonances are taken into account in constructing the reaction amplitudes to describe the experimental data. Three different models, i.e., the Feynman model, the Regge model, and the interpolated Regge model, are employed where the $t$ -channel reaction amplitudes are constructed in Feynman type, Regge type, and interpolated Regge type, respectively. The results show that in neither Feynman model with two nucleon resonances introduced nor interpolated Regge model with one nucleon resonances included, can the available data for $γ p \to f_{1} (1285) p$ be satisfactorily reproduced. Nevertheless, in the Regge model, when any one of the $N (1990) 7/2^{+}$ , $N (2000) 5/2^{+}$ , $N (2040) 3/2^{+}$ , $N (2060) 5/2^{-}$ , $N (2100) 1/2^{+}$ , $N (2120) 3/2^{-}$ , $N (2190) 7/2^{-}$ , $N (2300) 1/2^{+}$ , and $N (2570) 5/2^{-}$ resonances is considered, the data can be well described. The resulted resonance parameters are consistent with those advocated in Particle Data Group (PDG) review. Further analysis shows that in high-energy region, the peaks of $γ p \to f_{1} (1285) p$ differential cross sections at forward angles are dominated by the contributions from $t$ -channel $ρ$ - and $ω$ -exchange diagrams, while in low-energy region, the $s$ -channel pole diagrams of resonances also provide significant contributions to the $γ p \to f_{1} (1285) p$ cross sections.
↳ hep-phnucl-thCPC(2024)·1 citation
08
Validation of the $^{10} Be$ Ground-State Molecular Structure Using $^{10} Be (p, p α)^{6} He$ Triple Differential Reaction Cross-Section Measurements
P. J. Li🇨🇳 · D. Beaumel🇫🇷 · J. Lee🇨🇳 · M. Assié🇫🇷 · S. Chen🇨🇳 · S. Franchoo🇫🇷 · J. Gibelin🇫🇷 · F. Hammache🇫🇷 · T. Harada🇯🇵 · Y. Kanada-En'yo🇯🇵 · Y. Kubota🇯🇵 · S. Leblond🇨🇳 and 49 other authors
The cluster structure of the neutron-rich isotope $^{10}$ Be has been probed via the $(p, p α)$ reaction at 150 MeV/nucleon in inverse kinematics and in quasifree conditions. The populated states of $^{6}$ He residues were investigated through missing mass spectroscopy. The triple differential cross-section for the ground-state transition was extracted for quasifree angle pairs ( $θ_{p}$ , $θ_{α}$ ) and compared to distorted-wave impulse approximation reaction calculations performed in a microscopic framework using successively the Tohsaki-Horiuchi-Schuck-Röpke product wave-function and the wave-function deduced from Antisymmetrized Molecular Dynamics calculations. The remarkable agreement between calculated and measured cross-sections in both shape and magnitude validates the molecular structure description of the $^{10}$ Be ground-state, configured as an $α$ - $α$ core with two valence neutrons occupying $π$ -type molecular orbitals.
↳ nucl-exnucl-thPRL(2023)·41 citations
09
Space-like Electromagnetic Form Factors of Lambda- and Sigma-Baryons from Quark-Diquark Faddeev Equations
Langtian Liu🇨🇳 · Christian S. Fischer🇩🇪
An important goal of ongoing and future experiments is to explore spectra and transition form factors of baryons with non-zero strangeness. Of particular interest is the transition form factor $γ^{(*)} Σ^{0} \to Λ$ in the time-like momentum region that can be extracted from Dalitz decays. On the road towards a theoretical description of these form factors we extend a covariant dynamical quark-diquark model for the baryon Faddeev equation to the strange-quark sector. Based on an excellent description of the mass spectrum of selected baryon octet and decuplet states and reasonable results for the nucleon form factors we determine the elastic electromagnetic form factors of $Λ$ and $Σ^{+}, Σ^{0}, Σ^{-}$ hyperons in the space-like region as well as the ones for the octet transition $γ^{(*)} Σ^{0} \to Λ$ . We discuss qualitative and quantitative features of the diquark-quark picture and compare systematically with previous results from a three-body Faddeev approach and lattice data where available.
↳ hep-phnucl-thEPJA(2024)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE