118685388
Model for projectile fragmentation: Case study for Ni on Ta and Be, and Xe on Al
For projectile fragmentation we work out details of a model whose origin can be traced back to the Bevalac era. The model positions itself between the phenomenological EPAX parametrization and microscopic transport models like “Heavy Ion Phase Space Exploration Model”(HIPSE) and antisymmetrised molecular dynamics(AMD). We apply the model to some recent data of projectile fragmentation of Ni on Ta and Be at beam energy 140 MeV/nucleon and some older data of Xe on Al at beam energy 790 MeV/nucleon. Reasonable values of cross-sections for various composites populated in the reactions are obtained.
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
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.
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.
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.
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.
123623965
Observations on muon multiplicity distribution with the GRAPES-2 experiment at Ooty for studies on the mass composition of cosmic rays at PeV energies
Precise knowledge of the mass composition of the primary cosmic ray flux below and above the knee in the primary energy spectrum at E∼3×10 15 eV is essential for understanding the acceleration and propagation of high energy cosmic rays. Simulations have shown that the correlations between the electron and muon components of showers are very sensitive to the mass of the primary nuclei. In particular, different regions of the muon multiplicity distribution observed with a large area muon detector, for well-defined selection on the electron component of showers, have a high sensitivity to different nuclear groups present in the primary flux. The GRAPES-2 experiment at Ooty seeks to exploit this sensitivity using a 200m 2 area muon detector to study the mass composition of the primary flux in the energy range 10 14 -10 16 eV. The details of the experiment are presented and early observations are discussed in relation to the expectations from simulations.
119638891
Delayed energetic events in extensive air showers
Production of massive (> or =10 GeV/c/sup 2/) strongly interacting particles in very-high-energy interactions has been suggested by many theories. These particles, if produced in the cores of extensive air showers in the upper atmosphere, would arrive at the observational level delayed by tens of nanoseconds relative to all other known particles of similar energy, provided they are relatively stable (lifetime >10/sup -6/ s). Experiments searching for such particles have reported observing delayed (>20 ns) energetic (>40 GeV) events. However several anomalous features observed for these events have precluded their interpretation in terms of massive particles with ordinary hadronic interaction characteristics in a conclusive manner. We report here the details of a new experiment carried out at the Ooty laboratory during 1978--1981 where we have attempted to study the delayed energetic events with a multidetector system placed inside the large Ooty multiplate cloud chamber. Our observations show that the delayed energetic events could not be ascribed to high-energy hadronlike interactions of a massive strongly interacting particle. We have observed one delayed event showing a high-energy cascade in cloud chamber but inadequate timing information does not make a convincing case for this event to be due to a high-energy delayed massivemore » hadron. However this event combined with observation of two similar events earlier by Tonwar et al. suggest the existence of some interesting phenomenon requiring observations over a long period of time. We have obtained a 99% C.L. upper limit of 1.7 x 10/sup -11/ cm/sup -2/ s/sup -1/ sr/sup -1/ for the flux of massive particles in extensive air showers of size approx.(5 x 10/sup 4/)--(5 x 10/sup 6/) particles which corresponds to an upper limit of 2.5 x 10/sup -33/ cm/sup 2/ for the production cross section for particles of mass >10 GeV/c/sup 2/ at energies of approx.10/sup 5/--10/sup 7/ GeV.« less
122335370
Transverse energy distributions in participant number model for ultra-relativistic heavy-ion collisions
The transverse energy distribution in ultra-relativistic heavy-ion collisions has been obtained as a convolution over the number of projectile and target participants. The latter is computed using the geometrical overlap model as a function of impact parameter. The data from 10 A GeV to 200 A GeV heavy ion beams on various targets in different pseudo-rapidity domains have been successfully described.
120287039
Physics beyond instantons. Measuring the physical correlation length
In broken-symmetry phases of models with discrete global symmetry, the physical correlation length can be measured using time-slice correlators projected to non-zero momenta. A transfer matrix based argument is used to construct the finite-size scaling for this quantity. We extract the correlation length for the two-dimensional ten-state Potts model by this means, and the surface tension from the zero-momentum correlator.