121995970
A check on the geometrical assumptions in models of relativistic heavy ion collisions
Abstract The results of a recent experiment can be used to test clearly the geometrical assumptions of a variety of models for heavy ion collisions. Frequently used models are seen to fail quantitatively; the data show the need for incorporating nuclear transparency; both multiple and clean knockout collisions are needed.
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.
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.
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.
121836312
Excluded volume in nuclear fragmentation
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.
294813
Analytical description of classical trajectories and deflection function in scattering
Analytical expressions are derived for classical trajectories in repulsive Coulomb plus multi-step attractive potentials. Thereafter the closed form expressions are obtained for classical deflection functions. The expressions are expected to be of use in heavy ion interactions in nuclear physics.
128078572
A preshower photon multiplicity detector for the WA93 experiment
Abstract A fine granularity preshower detector has been designed, fabricated and installed in the WA93 experiment for the first ever measurement of photon multiplicity in ultra-relativistic heavy ion collisions. Photons are counted by detecting the preshower signal in plastic scintillator pads placed behind a lead converter and applying a threshold on the scintillator signal to reject the minimum ionizing particles. The photon detection efficiency estimated using Monte-Carlo and beam test results is found to be ∼65–75% depending on centrality. Simulation and performance results of the detector for counting of photons and rejection of hadrons in the large multiplicity environment of ultra-relativistic heavy ion collisions are described.
116940731
Dissipation, hydrodynamics and the fireball
We investigate the hydrodynamics of the QCD plasma using dimensionless numbers built from the thermodynamics and transport theory of the plasma and characteristic dimensions of the fireball produced in heavy-ion collisions. We find that by the usual measures, dissipation is strong, and the fireball is on the borderline of equilibrium. As a result, the system is richer in phenomena than ideal hydrodynamics would predict. One general implication is that it may be possible to get a direct view of the QCD plasma phase rather than having to infer its existence indirectly from signals that come from the freezeout isotherm after the fireball has cooled into the hadronic phase.
67811342
GRAPES-3¿A high-density air shower array for studies on the structure in the cosmic-ray energy spectrum near the knee
Abstract The change in the spectral index from about - 2.7 to - 3.1 at ∼ 3 × 10 15  eV in the all-particle energy spectrum of primary cosmic rays is very significant for learning about the nature of cosmic sources of ultra-high energy particles and their acceleration and propagation in the galactic disk. Any observation of a fine structure in the spectrum would be important for improving our understanding of these physical processes. The GRAPES-3 air shower array has been designed to achieve higher precision in determination of various shower parameters to enable observation of any fine structure in the energy spectrum, if it exists. The details of the shower detectors, shower trigger and the data acquisition system are presented here along with estimates of trigger efficiencies from Monte Carlo simulations for primary photons ( γ -rays) and several nuclei.
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.