Nuclear Theory·nucl-th

Thursday·November 23, 2023

9 papers—4 primary·5 cross-listed

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)·42 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)·40 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)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE

Numerical modelling of bulk viscosity in neutron stars

Magnetic field dependence of the neutral pion longitudinal screening mass in the linear sigma model with quarks

Analysis of the data for γp→f1​(1285)p photoproduction

Validation of the 10Be Ground-State Molecular Structure Using 10Be(p,pα)6He Triple Differential Reaction Cross-Section Measurements

Space-like Electromagnetic Form Factors of Lambda- and Sigma-Baryons from Quark-Diquark Faddeev Equations

Affiliations

Analysis of the data for $γ p \to f_{1} (1285) p$ photoproduction

Validation of the $^{10} Be$ Ground-State Molecular Structure Using $^{10} Be (p, p α)^{6} He$ Triple Differential Reaction Cross-Section Measurements