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Nuclear Theory·nucl-th

Tuesday·February 21, 2023

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 01

    Third-order relativistic dissipative fluid dynamics from the method of moments

    Caio V. P. de Brito🇧🇷 · Gabriel S. Denicol🇧🇷

    We derive a linearly causal and stable third-order relativistic fluid-dynamical theory from the Boltzmann equation using the method of moments. For this purpose, we demonstrate that such theory must include novel degrees of freedom, corresponding to irreducible tensors of rank 3 and 4. The equations of motion derived in this work are compared with numerical solutions of the Boltzmann equation, considering an ultrarelativistic, classical gas in the highly symmetric Bjorken flow scenario. These solutions are shown to be in good agreement for a wide range of values of shear viscosity and initial temperatures.

    nucl-thphysics.flu-dynPRD(2023)·29 citations
  2. 02

    Bayesian quantification of strongly-interacting matter with color glass condensate initial conditions

    Matthew R. Heffernan🇨🇦 · Charles Gale🇨🇦 · Sangyong Jeon🇨🇦 · Jean-François Paquet🇺🇸

    A global Bayesian analysis of relativistic Pb + Pb collisions at = 2.76 TeV is performed, using a multistage model consisting of an IP-Glasma initial state, a viscous fluid dynamical evolution, and a hadronic transport final state. The observables considered are from the soft sector hadronic final state. Posterior and Maximum a Posteriori parameter distributions that pertain to the IP-Glasma and hydrodynamic phases are obtained, including the shear and bulk specific viscosity of strong interacting matter. The first use of inference with transfer learning in heavy-ion analyses is presented, together with Bayes Model Averaging.

    nucl-thhep-phnucl-exPRC(2024)·55 citations
  3. 03

    Phenomenological Relativistic Second-Order Hydrodynamics for Multiflavor Fluids

    Arus Harutyunyan🇦🇲 · Armen Sedrakian🇩🇪

    In this work, we perform a phenomenological derivation of the first- and second-order relativistic hydrodynamics of dissipative fluids. To set the stage, we start with a review of the ideal relativistic hydrodynamics from energy-momentum and particle number conservation equations. We then go on to discuss the matching conditions to local thermodynamical equilibrium, symmetries of the energy-momentum tensor, decomposition of dissipative processes according to their Lorentz structure, and finally, the definition of the fluid velocity in the Landau and Eckart frames. With this preparatory work, we first formulate the first-order (Navier-Stokes) relativistic hydrodynamics from the entropy flow equation, keeping only the first-order gradients of thermodynamical forces. A generalized form of diffusion terms is found with a matrix of diffusion coefficients describing the relative diffusion between various flavors. The procedure of finding the dissipative terms is then extended to the second order to obtain the most general form of dissipative function for multiflavor systems up to the second order in dissipative fluxes. The dissipative function now includes in addition to the usual second-order transport coefficients of Israel-Stewart theory also second-order diffusion between different flavors. The relaxation-type equations of second-order hydrodynamics are found from the requirement of positivity of the dissipation function, which features the finite relaxation times of various dissipative processes that guarantee the causality and stability of the fluid dynamics. These equations contain a complete set of nonlinear terms in the thermodynamic gradients and dissipative fluxes arising from the entropy current, which are not present in the conventional Israel-Stewart theory.

    nucl-thastro-ph.HEhep-phSymmetry(2023)·6 citations
  4. 04

    Optical potential for incident and emitted low-energy particles. III. Non-statistical processes induced by neutrons on Zr, Nb, and Mo nuclei

    Marilena Avrigeanu · Vlad Avrigeanu

    The reliability of a previous -particle optical-model potential (OMP) on nuclei with mass number 45209 was proved for emitted particles as well, for proton--induced reactions on Zn isotopes [Phys. Rev. C {\bf 91}, 064611 (2015), Paper I]. However, the same was not the case of neutrons on Zr stable isotopes [Phys. Rev. C {\bf 96}, 044610 (2017), Paper II]. A recent assessment of this potential also for nucleon--induced -emission on 60 nuclei, including pickup direct reaction and eventual Giant Quadrupole Resonance (GQR) -emission, is completed for neutrons incident on Zr, Nb, and Mo stable isotopes. Consistent sets of input parameters, determined through analysis of independent data, is involved while no further empirical rescaling factors of the and nucleon widths have been involved. A suitable account of all competitive reaction channels is confirmed by careful uncertainty analysis, to avoid parameter ambiguities and/or error compensation. Additional validation of this potential is also supported by recently measured and cross--sections of Zr and Mo nuclei. An increase of the -emission beyond the statistical predictions, through consideration of additional reaction channels of the pickup direct interaction and {\it like}--GQR decay, makes possible the description of both absorption and emission of particles by the same optical potential.

    nucl-thnucl-exPRC(2023)·7 citations
  5. 05

    Pion production in intermediate-energy heavy-ion collisions with a relativistic quantum molecular dynamics model

    Si-Na Wei🇨🇳 · Zhao-Qing Feng🇨🇳

    The relativistic mean field approach by distinguishing \com{the slope of symmetry energy} is implemented into the Lanzhou quantum molecular dynamics transport model (LQMD.RMF). The collective flows in the isotopic nuclear reactions are systematically investigated by the relativistic quantum molecular dynamics model \com{with various slopes of symmetry energy}. The structure of the directed and elliptic flows is consistent with the results of the nonrelativistic transportation of nucleon system. \com{The directed flow difference between free neutrons and protons appears in the midrapidity region. The transverse momentum spectra of production is close to each other in the nearly symmetric system and the neutron-rich system. However, since there are more neutron-neutron scatterings in neutron-rich system, the transverse momentum spectra of production in the neutron-rich system are higher than one in the nearly symmetric system. For a given reaction system, the transverse momentum spectra of and production are independent on the stiffness of symmetry energy. This leads to the fact that the single ratio and the double ratio are independent on the stiffness of symmetry energy. Moreover, the double ratio without the -nucleon potential decreases with increasing the transverse momentum. However, the double ratio with the inclusion of potential increases with increasing the transverse momentum.

    nucl-th0 citations
  6. 06

    Revisiting the Gamow Factor of Reactions on Light Nuclei

    Eunseok Hwang · Heamin Ko · Kyoungsu Heo · Myung-Ki Cheoun · Dukjae Jang

    This study provides an improved understanding of the penetration probabilities (PPs) in nuclear reactions of light nuclei by correcting the assumptions used in the conventional Gamow factor. The Gamow factor effectively describes the PP in nuclear reactions based on two assumptions: low particle energy than the Coulomb barrier and neglecting the dependence of nuclear interaction potential. However, we find that the assumptions are not valid for light nuclei. As a result of a calculation that excludes the assumptions, we obtain the PP that depends on the nuclear interaction potential depth for the light nuclei. For the potential depth fitted by the experimental fusion cross-section, we present that PPs of light nuclei (D+D, D+T, D+He, p+D, p+Li, and p+Li) become higher than the conventional one near the Coulomb barrier. We also discuss the implications of the modified PP, such as changes in the Gamow peak energy, which determine the measurement of the energy range of the nuclear cross-section in experiments, and the electron screening effect.

    nucl-thastro-ph.SRnucl-exApJ(2023)·3 citations

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first authorsco-authorsvia INSPIRE