In-medium effects for nuclear matter in the Fermi energy domain

Abstract

We study nuclear stopping in central collisions for heavy-ion induced reactions in the Fermi energy domain, between $15$ and $100$ A\,\textrm{MeV}. Using the large dataset of exclusive measurements provided by the $4\pi$ array \emph{INDRA}, we determine the relative degree of stopping as a function of system mass and bombarding energy. We show that the stopping can be directly related to the transport properties in the nuclear medium. By looking specifically at free nucleons (here protons), we present for the first time a comprehensive body of experimental results concerning the mean free path, the nucleon-nucleon cross-section and in-medium effects in nuclear matter. It is shown that the mean free path exhibits a maximum at ${\lambda }_{NN}=9.5\pm 2$ \textrm{fm}, around $E_{inc}=35-40$ A\,\textrm{MeV} incident energy and decreases toward an asymptotic value ${\lambda }_{NN}=4.5\pm 1$ \textrm{fm} at $E_{inc}=100$ A\,\textrm{MeV}. After accounting for Pauli blocking of elastic nucleon-nucleon collisions, it is shown that the effective in-medium \emph{NN} cross section is further reduced compared to the free value in this energy range. Therefore, in-medium effects cannot be neglected in the Fermi energy range. These results bring new fundamental inputs for microscopic descriptions of nuclear reactions in the Fermi energy domain.

arXiv comment9 pages, 10 figures, submitted to PRC

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• Comparison of AMD calculations with experimental data for peripheral collisions of 93Nb+93Nb,116Sn at 38 MeV/nucleon
• Aspects of the momentum dependence of the equation of state and of the residual $NN$ cross section, and their effects on nuclear stopping
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• Mean free path and shear viscosity in central ${}^{129}$Xe+${}^{119}$Sn collisions below 100 MeV/nucleon
• Effect of energy conservation on in-medium $\mbox{NN}\to \mbox{N}Δ$ cross section in isospin-asymmetric nuclear matter
• Reaction and fusion cross sections for the near-symmetric system ${}^{129}Xe{+}^{nat}Sn$ from $8$ to $35$ $AMeV$
• Effects of neutron-skin thickness on direct hard photon emission from reactions induced by the neutron-rich projectile ${}^{50}$Ca
• From the liquid drop model to lattice QCD
• The cumulants of the baryon number from central Au+Au collision at $E_{lab}$= 1.23 GeV$/$nucleon reveal the nuclear mean-field potentials
• In-medium $\mbox{NN}\to \mbox{N}Δ$ cross section and its dependence on effective Lagrange parameters in isospin-asymmetric nuclear matter
• Study and validation of a new "3D Calorimetry" of hot nuclei with the HIPSE event generator
• Isospin diffusion from ${}^{40,48}$Ca${+}^{40,48}$Ca experimental data at Fermi energies: Direct comparisons with transport model calculations
• Dynamical description of heavy-ion collisions at Fermi energies
• A new "3D Calorimetry" of hot nuclei
• Evolutions of in-medium baryon-baryon scattering cross sections and stiffness of dense nuclear matter from Bayesian analyses of FOPI proton flow excitation functions
• The influence of $\delta$ meson on the isospin splitting of in-medium $NN\to N\Delta$ cross sections
• Azimuthal anisotropy and multiplicities of hard photons and free nucleons in intermediate-energy heavy-ion collisions
• Revisiting an extended-mean-field approach in heavy-ion collisions around the Fermi energy
• Constraining neutron-proton effective mass splitting through nuclear giant dipole resonance within transport approach
• Influence of Cluster Configurations and Nucleon--Nucleon Scattering Cross-Section on Stopping Power in Heavy-Ion Collisions
• Sensitivity of the Mean Field Dynamics to the Spatial Distribution in Nuclear One-body Dissipations