8684751
Incorporating radial flow in the lattice gas model for nuclear disassembly
We consider extensions of the lattice gas model to incorporate radial flow. Experimental data are used to set the magnitude of radial flow. This flow is then included in the Lattice Gas Model in a microcanonical formalism. For magnitudes of flow seen in experiments, the main effect of the flow on observables is a shift along the $E^*/A$ axis.
14927510
A Transport Model for Nuclear Reactions Induced by Radioactive Beams
Major ingredients of an isospin and momentum dependent transport model for nuclear reactions induced by radioactive beams are outlined. Within the IBUU04 version of this model we study several experimental probes of the equation of state of neutron‐rich matter, especially the density dependence of the nuclear symmetry energy. Comparing with the recent experimental data from NSCL/MSU on isospin diffusion, we found a nuclear symmetry energy of Esym(ρ) ≈ 31.6(ρ/ρ0)1.05 at subnormal densities. Predictions on several observables sensitive to the density dependence of the symmetry energy at supranormal densities accessible at GSI and the planned Rare Isotope Accelerator (RIA) are also made.
16308546
First Order Phase Transition in Intermediate-Energy Heavy Ion Collisions
We model the disassembly of an excited nuclear system formed as a result of a heavy ion collision. We find that, as the beam energy in central collisions in varied, the dissociating system crosses a liquid-gas coexistence curve, resulting in a first-order phase transition. Accessible experimental signatures are identified: a peak in specific heat, a power-law yield for composites, and a maximum in the second moment of the yield distribution.
119186084
Bimodality and Coulomb effects with a canonical thermodynamic model
Abstract The effect of the Coulomb interaction on the phase diagram of finite nuclei is studied within the Canonical Thermodynamic Model. If Coulomb effects are artificially switched off, this model shows a phenomenology consistent with the liquid–gas phase transition. The inclusion of Coulomb does not significantly affect the phase diagram but it drastically modifies the nature and order parameter of the transition. A clear understanding of the phenomenon can be achieved looking at the distribution of the largest fragment produced in each fragmentation event. Possible connections with experimental observations are outlined.
2820708
Transverse momenta, nuclear equation of state, and momentum-dependent interactions in heavy-ion collisions.
We investigate the generation of transverse momentum in high-energy heavy-ion collisions and its relation to the nuclear equation of state. We find that streamer chamber data can be fitted by Boltzmann-Uehling-Uhlenbeck calculations with a momentum-dependent potential that closely models realistic nuclear matter interactions and yields an equation of state with {ital K}=215 MeV.
121836312
Excluded volume in nuclear fragmentation
119974560
Eikonal model description of forward energy distribution in oxygen-induced reactions at 60 A GeV and 200 A GeV
The forward energy flow cross section is described in terms of the projectile-nucleon abrasion probability which is calculated in the impact parameter representation within the framework of the Glauber multiple scattering formalism. Realistic nuclear densities and the nucleon-nucleon inelastic cross section have been used in the calculation. The recent WA80 data are in reasonable agreement with the calculation. A simple relationship has been obtained between the abrased nucleons from the target and projectile and the zero degree energy.
121879312
Isobaric analog impurity from total and differential neutron scattering cross sections of silicon
Resonance parameters for sour resonances in Si have been obtained by analyzing measured differential neutron scattering cross sections combined with the total neutron cross section in the neutron energy range 1.05--1.40 MeV and applying R-matrix single channel multilevel theory. The resonance at 1254 krB has been identified as the s-wave analog resonance in /sup 29/Si. The identification also takes into account experimental radiative neutron capture data and shell model calculations for the radiative width. Estimates of the isospin mixing matrix elements are given.
120844876
New results from ooty eas array for cosmic sources at PeV energies: CYGNUS X-3, Crab pulsar and Sco X-1
Abstract Ooty group has reported detection of a steady signal from Cyg X-3 based on observations made during 1984–1986 through detection of a directional excess. Further analysis of data has revealed a significant flux enhancement during April 1986, confirming observations reported by the CYGNUS group at Los Alamos and the Baksan group. These results show conclusively that the flux from Cyg X-3 is variable over a time scale of few weeks. We also report here the details of an unusual burst from Cyg X-3, consisting of 5 showers in 13 minutes, on June 19, 1985, which shows the variability of the flux from Cyg X-3 on a much shorter time scale of few minutes. Our analysis of showers arriving from the direction of the Crab pulsar has shown only a small time-averaged excess. But these data, when folded with the Crab pulsar period, show a very significant excess at the expected phase of the optical interpulse. This is the first detection of 33 ms pulsation in the PeV energy flux from the Crab pulsar. The exact alignment of the phase of emission over nearly 20 decades of energy, from meter wavelengths to PeV, makes the Crab pulsar a really unique source to study and understand details of mechanisms for emission and acceleration of particles in compact sources. We also present here a discussion of our observations on another x-ray binary, Sco X-1. Ooty data show a very significant excess in the number of showers from the direction of Sco X-1 during a two month period in 1986, in agreement with observations reported by the Mt. Chacaltaya group. These observations establish this x-ray binary as another important source of PeV energy radiation.
119853101
Jet production from nuclei and the cumulative region in nuclear structure functions
Abstract We show that recent data on nuclear dependence of large- E T jet production in proton-nucleus collisions can be accounted for by the nuclear dependence of structure functions, in the framework of lowest order perturbative QCD. A crucial role seems to be played by the extension of nuclear structure functions in the region x > 1 (cumulative region). Such an extension is expected in some models of nuclear effects.
123705690
Stringy restrictions on the Scherk-Schwarz mechanism
The authors consider the sigma model describing the propagation of a bosonic string in a manifold of the type M4(X)K obtained by compactification of D=26 spacetime using the Scherk-Schwarz mechanism. The requirement of 2D conformal invariance (at the 1-loop level) of this sigma model is shown to impose rather stringent restrictions on the mass parameters used in the Scherk-Schwarz mechanism. Implications for the background field mass spectrum in the model considered by Scherk and Schwarz (1979) are examined.