Multifragmentation through Exotic Shape Nuclei in alpha(5GeV/u) + Au Reactions

We simulate the fragmentation processes in the {$\alpha$~$+$~Au~} collisions at a bombarding energy of 5 GeV/u using the simplified RQMD approach plus the statistical decay model. We find from the simulation that the angular-distribution of the intermediate mass fragments has a sideward peak, more strongly in the transverse direction than in the beam-direction, when the intermediate nucleus formed by the dynamical process has an annular eclipse shape, which explains the experimental results.Comment: 11pages, Rectex is used, 3 Color-Postscript figures are also available by request from [email protected]

Simulation of Transitions between "Pasta" Phases in Dense Matter

Calculations of equilibrium properties of dense matter predict that at subnuclear densities nuclei can be rodlike or slablike. To investigate whether transitions between phases with non-spherical nuclei can occur during the collapse of a star, we perform quantum molecular dynamic simulations of the compression of dense matter. We have succeeded in simulating the transitions between rodlike and slablike nuclei and between slablike nuclei and cylindrical bubbles. Our results strongly suggest that non-spherical nuclei can be formed in the inner cores of collapsing stars.Comment: 4 pages, 4 figures, final version published in Phys. Rev. Lett., high-res figures can be seen at http://www.nordita.dk/~gentaro/research/fig

Integrated Simulation of Fragmentation, Evaporation, and Gamma-decay Processes in the Interaction of Cosmic-ray Heavy Ions with the Atmosphere using PHITS

General-purpose Monte-Carlo radiation tranport calculation code PHITS is applied to calculate prompt gamma-ray emission from cosmic-ray heavy ions fragmented in the atmosphere. Event-by-event simulation of spallation reactions by cosmic-ray heavy ions was performed by combination of three reaction models, responsible for different reaction phases

Analysis of proton-induced fragment production cross sections by the Quantum Molecular Dynamics plus Statistical Decay Model

The production cross sections of various fragments from proton-induced reactions on $^{56}$Fe and $^{27}$Al have been analyzed by the Quantum Molecular Dynamics (QMD) plus Statistical Decay Model (SDM). It was found that the mass and charge distributions calculated with and without the statistical decay have very different shapes. These results also depend strongly on the impact parameter, showing an importance of the dynamical treatment as realized by the QMD approach. The calculated results were compared with experimental data in the energy region from 50 MeV to 5 GeV. The QMD+SDM calculation could reproduce the production cross sections of the light clusters and intermediate-mass to heavy fragments in a good accuracy. The production cross section of $^{7}$Be was, however, underpredicted by approximately 2 orders of magnitude, showing the necessity of another reaction mechanism not taken into account in the present model.Comment: 12 pages, Latex is used, 6 Postscript figures are available by request from [email protected]

Quantum Molecular Dynamics Approach to the Nuclear Matter Below the Saturation Density

Quantum molecular dynamics is applied to study the ground state properties of nuclear matter at subsaturation densities. Clustering effects are observed as to soften the equation of state at these densities. The structure of nuclear matter at subsaturation density shows some exotic shapes with variation of the density.Comment: 21 pages of Latex (revtex), 9 Postscript figure

Analysis of the (N,xN') reactions by quantum molecular dynamics plus statistical decay model

We propose a model based on quantum molecular dynamics (QMD) incorporated with statistical decay model (SDM) to describe various nuclear reactions in an unified way. In this first part of the work, the basic ingredients of the model are defined and the model is applied systematically to the nucleon(N)-induced reactions. It has been found that our model can give a remarkable agreement in the energy-angle double differential cross sections of (N,xN') type reactions for incident energies from 100 MeV to 3 GeV with a fixed parameter set. An unified description of the major three reaction mechanisms of (N,xN') reactions, i.e. compound, pre-equilibrium and spallation processes, is given with our model

Non-Markovian large amplitude motion and nuclear fission

The general problem of dissipation in macroscopic large-amplitude collective motion and its relation to energy diffusion of intrinsic degrees of freedom of a nucleus is studied. By applying the cranking approach to the nuclear many body system, a set of coupled dynamical equations for the collective classical variables and the quantum mechanical occupancies of the intrinsic nuclear states is derived. Different dynamical regimes of the intrinsic nuclear motion and its consequences on time properties of collective dissipation are discussed. The approach is applied to the descant of the nucleus from the fission barrier.Comment: 9 pages and 3 figure