Neck fragmentation reaction mechanism

Abstract

Based on a microscopic transport model, we study the origin of nonstatistical Intermediate Mass Fragment ($IMF$) production in semicentral heavy ion collisions at the Fermi energies. We show that a fast, dynamical $IMF$ formation process, the {\it neck fragmentation mechanism}, can explain the experimentally observed features: deviations from Viola systematics and anisotropic, narrow angular distributions. It may be regarded as the continuation of the multifragmentation mechanism towards intermediate impact parameters. Its relation to other dynamical mechanisms, the induced fission and the abrasion of the spectator zones, that can also contribute to mid-rapidity $IMF$ production, is discussed. The dependence on beam energy and centrality of the collision is carefully analysed. The competition between volume and surface instabilities makes this mechanism very sensitive to the in-medium nucleon-nucleon interactions, from the cross sections for hard collisions to the compressibility and other Equation of State ($EOS$) properties. For charge asymmetric collisions the sensitivity of various observables to the symmetry energy is investigated. Of particular interest appears the isospin diffusion dynamics with no signal of isospin equilibration. However, in spite of the short time scales and of the dynamical aspects, we notice isoscaling features of the neck mechanism. We observe that isospin enrichement of the neck zone as well as the isoscaling parameters are sensitive to the density dependence of asymmetry term of EOS around and below saturation value.

29 pages, 20 figures

References in corpus (13)

• Isotopic Scaling in Nuclear Reactions
• Isospin Fractionation in Nuclear Multifragmentation
• Neutron-Proton Differential Flow as a Probe of Isospin-Dependence of Nuclear Equation of State
• Isospin effects in Nuclear Fragmentation
• Spinodal decomposition of low-density asymmetric nuclear matter
• Dynamical effects in multifragmentation at intermediate energies
• Isotopic Scaling of Heavy Projectile Residues from the collisions of 25 MeV/nucleon 86Kr with 124Sn, 112Sn and 64Ni, 58Ni
• Enhanced Production of Neutron-Rich Rare Isotopes in Peripheral Collisions at Fermi Energies
• Space and Time pattern of mid-velocity IMF emission in peripheral heavy-ion collisions at Fermi energies
• Study of intermediate velocity products in the Ar+Ni collisions between 52 and 95 A.MeV
• Fragmentation in Peripheral Heavy-Ion Collisions: from Neck Emission to Spectator Decays
• Fragment Production in Non-central Collisions of Intermediate Energy Heavy Ions
• Contemporary presence of dynamical and statistical production of intermediate mass fragments in midperipheral ${}^{58}$Ni+${}^{58}$Ni collisions at 30 MeV/nucleon

Cited by in corpus (31)

• Reaction Dynamics with Exotic Beams
• Probing the Nuclear Symmetry Energy with Heavy Ion Collisions
• Correlations between emission timescale of fragments and isospin dynamics in ${}^{124}$Sn+${}^{64}$Ni and ${}^{112}$Sn+${}^{58}$Ni reactions at 35 AMeV
• Isospin Transport at Fermi Energies
• Nuclear dynamics and particle production near threshold energies in heavy-ion collisions
• Isospin Dynamics in Peripheral Heavy Ion Collisions at Fermi Energies
• The Influence of in-medium NN cross-sections, symmetry potential and impact parameter on the isospin observables
• Experimental effects on dynamics and thermodynamics in nuclear reactions on the symmetry energy as seen by the CHIMERA 4$\pi$ detector
• Isospin transport in 84Kr + 112,124Sn collisions at Fermi energies
• IMF isotopic properties in semi-peripheral collisions at Fermi energies
• The Dynamical Dipole Mode in Fusion Reactions with Exotic Nuclear Beams
• Isospin Distillation with Radial Flow: a Test of the Nuclear Symmetry Energy
• Symmetry Energy Effects on Fusion Cross Sections
• Particle and light fragment emission in peripheral heavy ion collisions at Fermi energies
• Dynamical fission of the quasiprojectile and isospin equilibration for the system 80Kr+ 48 Ca at 35 MeV/nucleon
• Comparison of AMD calculations with experimental data for peripheral collisions of 93Nb+93Nb,116Sn at 38 MeV/nucleon
• Isospin dynamics on neck fragmentation in isotopic nuclear reactions
• Isospin Dynamics in Heavy Ion Collisions: EoS-sensitive Observables
• Alpha Conjugate Neck Structures in the Collisions of 35 MeV/nucleon 40Ca with 40Ca
• Competition between Coulomb and Symmetry Potential in Semi-peripheral Heavy-ion Collisions
• Experimental study of the isospin transport with 40,48 Ca+ 40,48 Ca reactions at 35 MeV/nucleon
• Exotic break-up modes in heavy ion reactions at low energies
• Energetics of midvelocity emissions in peripheral heavy ion collisions at Fermi energies
• Experimental study of the ${}^{40,48}$Ca+ ${}^{40,48}$Ca reactions at 35 MeV/nucleon
• Fragment Formation in Central Heavy Ion Collisions at Relativistic Energies
• Constraining the Symmetry Energy: A Journey in the Isospin Physics from Coulomb Barrier to Deconfinement
• Isospin compositions of correlated sources in the Fermi energy domain
• The Dynamical Dipole Radiation in Dissipative Collisions with Exotic Beams
• Revisit to the yield ratio of triton and ${}^3$He as an indicator of neutron-rich neck emission
• Probing the symmetry energy with isospin ratio from nucleons to fragments
• Correlations between isospin dynamics and Intermediate Mass Fragments emission time scales: a probe for the symmetry energy in asymmetric nuclear matter