Nuclear Theory·nucl-th
24 papers—17 primary·7 cross-listed
Viktor Begun🇵🇱 · Maja Mackowiak-Pawlowska🇵🇱
We summarize the new method for the correction of participant fluctuations in high energy nucleus-nucleus collisions. It allows to estimate a fluctuation baseline in comparison to a useful signal. In particular cases of a weak signal compared to baseline, it allows to cancel the baseline contribution from participants.
Mary Alberg🇺🇸 · Gerald A. Miller🇺🇸
The light-quark flavor dependence of the proton sea has been of great interest for many years because of its close connection with non-perturbative effects. One hypothesis is that this dependence arises from the pion cloud of the proton. We apply light cone perturbation theory and experimental constraints to a chiral Lagrangian to compute the relevant Fock-space components of the nucleon wave function with well-defined uncertainties. Existing experimental information regarding the light flavor sea is studied, and predictions for future experimental results are provided. Future experiments have the ability to rule out this hypothesis and have profound implications for understanding the nucleon-nucleon force.
Paul Romatschke🇺🇸 · Ulrike Romatschke🇺🇸
Ten years ago, relativistic viscous fluid dynamics was formulated from first principles in an effective field theory framework, based entirely on the knowledge of symmetries and long-lived degrees of freedom. In the same year, numerical simulations for the matter created in relativistic heavy-ion collision experiments became first available, providing constraints on the shear viscosity in QCD. The field has come a long way since then. We present the current status of the theory of non-equilibrium fluid dynamics in 2017, including the divergence of the fluid dynamic gradient expansion, resurgence, non-equilibrium attractor solutions, the inclusion of thermal fluctuations as well as their relation to microscopic theories. Furthermore, we review the theory basis for numerical fluid dynamics simulations of relativistic nuclear collisions, and comparison of modern simulations to experimental data for nucleus-nucleus, nucleus-proton and proton-proton collisions.
Matteo Vorabbi🇨🇦 · Angelo Calci🇨🇦 · Petr Navratil🇨🇦 · Michael K.G Kruse🇺🇸 · Sofia Quaglioni🇺🇸 · Guillaume Hupin🇫🇷
The exotic He nucleus, which presents one of the most extreme neutron-to-proton ratios, belongs to the isotonic chain famous for the phenomenon of ground-state parity inversion with decreasing number of protons. Consequently, it would be expected to have an unnatural (positive) parity ground state similar to Be and Li. Despite many experimental and theoretical investigations, its structure remains uncertain. Apart from the fact that it is unbound, other properties including the spin and parity of its ground state and the very existence of additional low-lying resonances are still a matter of debate. In this work we study the properties of He by analyzing the He continuum in the context of the ab initio no-core shell model with continuum (NCSMC) formalism with chiral interactions as the only input. The NCSMC is a state-of-the-art approach for the ab initio description of light nuclei. With its capability to predict properties of bound states, resonances, and scattering states in a unified framework, the method is particularly well suited for the study of unbound nuclei such as He. Our analysis produces an unbound He nucleus. Two resonant states are found at the energies of and MeV, respectively, above the He breakup threshold. The first state has a spin-parity assignment of and can be associated with the ground state of He, while the second, broader state has a spin-parity of . No resonance is found in the channel, only a very weak attraction. We find that the He ground-state resonance has a negative parity and thus breaks the parity-inversion mechanism found in the Be and Li nuclei of the same isotonic chain.
J. Eric Lynn🇺🇸 · Patrick Talou🇺🇸 · Olivier Bouland🇫🇷
The process is reviewed in light of modern nuclear reaction calculations in both slow and fast neutron-induced fission reactions on U and Pu. Observed fluctuations of the average prompt fission neutron multiplicity and average total -ray energy below 100 eV incident neutron energy are interpreted in this framework. The surprisingly large contribution of the M1 transitions to the pre-fission -ray spectrum of Pu is explained by the dominant fission probabilities of 0 and transition states, which can only be accessed from compound nucleus states formed by the interaction of -wave neutrons with the target nucleus in its ground state, and decaying through M1 transitions. The impact of an additional low-lying M1 scissors mode in the photon strength function is analyzed. We review experimental evidence for fission fragment mass and kinetic energy fluctuations in the resonance region and their importance in the interpretation of experimental data on prompt neutron data in this region. Finally, calculations are extended to the fast energy range where corrections can account for up to 3\% of the total fission cross section and about 20\% of the capture cross section.
The difference of the moment of inertia of the neutron star PSR J0348 + 0432 and that of its proto neutron star is studied in the framework of the relativistic mean field theory considering baryon octet. The temperature of the proto neutron star PSR J0348+0432 is chosen as T=5 MeV. The calculations show that the central baryon number density of the proto neutron star PSR J0348+0432 is in the range 0.6230.813 fm, decreased by 27\% compared to that of the neutron star PSR J0348+0432. The radius of the proto neutron star PSR J0348+0432 is in the range 13.10112.419 km, increased by 12\% compared to that of the neutron star PSR J0348+0432. The moment of inertia of the proto neutron star PSR J0348+0432 is in the range 1.939101.63810 g.cm, increased by about 27\% compared to that of the neutron star PSR J0348+0432.
Alina Czajka🇨🇦 · Sigtryggur Hauksson🇨🇦 · Chun Shen🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
This paper presents how thermal mean field effects are incorporated consistently in the hydrodynamical modelling of heavy-ion collisions. The nonequilibrium correction to the distribution function resulting from a temperature-dependent mass is obtained in a procedure which automatically satisfies the Landau matching condition and is thermodynamically consistent. The physics of the bulk viscosity is studied here for Boltzmann and Bose-Einstein gases within the Chapman-Enskog and 14-moment approaches in the relaxation time approximation. Constant and temperature-dependent masses are considered in turn. It is shown that, in the small mass limit, both methods lead to the same value of the ratio of the bulk viscosity over its relaxation time. The inclusion of a temperature-dependent mass leads to the emergence of the -function in that ratio, and it is of the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case it is affected by the infrared cut-off. This suggests that the relaxation time approximation may be too crude to obtain a reliable form of for gases obeying Bose-Einstein statistics.
Ad. R. Raduta (IFIN-HH, Bucharest)🇷🇴 · F. Gulminelli (LPC, Caen)🇫🇷
The effect of correlations between the slope and the curvature of the symmetry energy on ground state nuclear observables is studied within the extended Thomas-Fermi approximation. We consider different isovector probes of the symmetry energy, with a special focus on the skin of . We use a recently proposed meta-modelling technique to generate a large number of equation of state models, where the empirical parameters are independently varied. The results are compared to a set of calculations using 17 different Skyrme interactions. We show that the curvature parameter plays a non-negligible role on the neutron skin, while the effect is reduced in Skyrme functionals because of the correlation with the slope parameter.
The electric dipole moment is a very sensitive probe of CP violation beyond the standard model. Light nuclei are particularly interesting since the CP violation may be enhanced by nuclear many-body effects. In this proceeding, we present the current status of the theoretical evaluations of the electric dipole moment of light nuclei in the ab initio approach and in the cluster model. We add the preliminary result of the evaluation of the electric dipole moment of Li which is treated in a cluster model with a triton.
We study chiral symmetry restoration and quark deconfinement beyond mean field approximation in a magnetized PNJL model. The feedback from mesons to quarks modifies the quark coupling constant and Polyakov potential. As a result, the separate critical temperatures for the two phase transitions at mean field level coincide and the magnetic catalysis becomes inverse magnetic catalysis, when the meson contribution is included.
We present predictions for proton skins based on isospin-asymmetric equations of state derived microscopically from high-precision chiral few-nucleon interactions. Moreover, we investigate the relation between the neutron skin of a nucleus and the difference between the proton radii of the corresponding mirror nuclei.
We delineate the properties of dense QCD matter through equations of state constrained by the neutron star observations. The two solar mass constraint, the radius constraint of 11-13 km, and the causality constraint on the speed of sound, are used to develop the picture of hadron-quark continuity in which hadronic matter continuously transforms into quark matter. A unified equation of state at zero temperature and beta-equilibrium is constructed by a phenomenological interpolation between nuclear and quark matter equations of state. For applications to supernovae and neutron star mergers, the unified equation of state is perturbed by temperature corrections.
Takayasu Sekihara (JAEA, Ibaraki)🇯🇵 · Hiroyuki Fujioka (Kyoto U.)🇯🇵 · Takatsugu Ishikawa (ELPH, Tohoku Univ.)🇯🇵
We theoretically investigate a possibility of an bound state and its formation in the reaction. First, in the fixed center approximation to the Faddeev equations we obtain an bound state with a binding energy of 25 MeV and width of 19 MeV, where we take the interaction with a coupling to the channel from the linear model. Then, in order to investigate the feasibility from an experimental point of view, we calculate the cross section of the reaction at the photon energy in the laboratory frame around 1.2 GeV. As a result, we find a clear peak structure with the strength 0.2 nb/sr, corresponding to a signal of the bound state in case of backward emission. This structure will be prominent because a background contribution coming from single-step emission off a bound nucleon is highly suppressed. In addition, the signal can be seen even in case of forward emission as a bump or dip, depending on the relative phase between the bound-state formation and the single-step background.
Drawing largely from my work with co--workers, I present arguments that strangeness does not play an {\it explicit} role in compact-star matter. They are based on the skyrmion description of dense matter combined with Wilsoninan renormalization group approach to kaon nuclear interactions. The key idea is that quark degrees of freedom, carrying strangeness, can be traded in by topology for hadron degrees of freedom.
Utsab Gangopadhyaya🇮🇳 · Snigdha Ghosh🇮🇳 · Sourav Sarkar🇮🇳
The relativistic kinetic theory approach has been employed to study four well-known transport coefficients that characterize heat flow and diffusion for the case of a hot mixture constituting of nucleons and pions. Medium effects on the cross-section for binary collisions (,) have been taken into consideration by incorporating self-energy corrections to modify the propagator of the exchanged baryon in interaction and the and meson propagators for the case of interaction. The temperature dependence of the four coefficients have been investigated for several values of the baryon chemical potential.
Jaroslava Hrtánková🇨🇿 · Jiří Mareš🇨🇿
We studied the interactions with the nuclear medium within the 2009 version of the Paris potential model. We constructed the --nucleus optical potential using the Paris - and -wave scattering amplitudes and treated their strong energy and density dependence self-consistently. We considered a phenomenological -wave term as well. We calculated binding energies and widths of the bound in various nuclei. The -wave potential has very small effect on the calculated binding energies, however, it reduces the corresponding widths noticeably. Moreover, the -wave potential based on the Paris amplitudes supplemented by a phenomenological -wave term yields the binding energies and widths in very good agreement with those obtained within the RMF model consistent with -atom data.
Tomoya Naito · Ryosuke Akashi · Haozhao Liang
We test the Coulomb exchange and correlation energy density functionals of electron systems for atomic nuclei in the local density approximation (LDA) and the generalized gradient approximation (GGA). For the exchange Coulomb energies, it is found that the deviation between the LDA and GGA ranges from around in to around in , by taking the Perdew-Burke-Ernzerhof (PBE) functional as an example of the GGA\@. For the correlation Coulomb energies, it is shown that those functionals of electron systems are not suitable for atomic nuclei.
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