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.
14530230
Temperature determination from the lattice gas model.
Determination of temperature from experimental data has become important in searches for critical phenomena in heavy-ion collisions. Widely used methods are ratios of isotopes (which rely on chemical and thermal equilibrium), population ratios of excited states, etc. Using the lattice gas model we propose a new observable: {ital n}{sub ch}/{ital Z} where {ital n}{sub ch} is the charge multiplicity and {ital Z} is the charge of the fragmenting system. We show that the reduced multiplicity is a good measure of the average temperature of the fragmenting system. {copyright} {ital 1996 The American Physical Society.}
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.
15293327
Liquid-Gas Phase Transition in Nuclear Multifragmentation
Heavy-ion collisions allow one to pump energy into a nuclear system. In central collisions of equal size nuclei one can also create a significant amount of compression using high energy nuclear beams. The possibility of studying nuclei far from normal conditions raises the question: can we study phase transitions in nuclei similar, for instance, to the way, one can study phase transition in water? This is the subject of the present article.
14037021
Double asymptotic scaling in Drell-Yan processes
Double scaling may be observed in the Drell-Yan process at the Tevatron and in the ALICE detector at the Large Hadron Collider in a window of masses. In the double scaling limit of the cross section, the higher order QCD corrections are quite large, and are driven by the rise in gluon densities in the double scaling regime. The naive parton model cannot be valid even at asymptotic energies in the region of phase space where double scaling holds.
123088134
Proton optical model potential at sub-Coulomb energies for medium weight nuclei
The ($p$,$n$) reaction excitation functions for eleven nuclei from $A=45 \mathrm{to} 80$ measured at proton energies below \ensuremath{\sim}5 MeV have been analyzed utilizing the optical model. The real potential parameters used in the present work have been obtained by suitably combining the proton optical model parameters determined between 3 and 60 MeV. Large energy dependence of the real potential at energies below 5 MeV has been observed. The imaginary potential depths determined in the present analysis exhibit an anomalous behavior when plotted as a function of mass number $A$. By utilizing the low and intermediate energy proton data, an attempt has been made to obtain a "global" set of optical parameters in the proton energy range between 4 and 180 MeV, for medium weight nuclei.
14212919
Interface tensions and perfect wetting in the two-dimensional seven-state Potts model
Abstract We present a numerical determination of the order-disorder interface tension, σ od , for the two-dimensional seven-state Potts model. We find σ od = 0.0114 ± 0.0012, in good agreement with expectations based on the conjecture of perfect wetting. We take into account systematic effects on the technique of our choice: the histogram method. Our measurements are performed on rectangular lattices, so that the histograms contain identifiable plateaus. The lattice sizes are chosen to be large compared to the physical correlation length. Capillary wave corrections are applied to our measurements on finite systems.
122594393
Minijets and associated production of photons and muons in high energy heavy ion collisions
Due to the large hadronic multiplicities involved in heavy ion collisions at LHC energies, production of photons and muons inside jets cannot be distinguished from production in isolation. Associated production rates for photons and muons in minijets are estimated. It is found that the muon cross section per uranium-uranium collision could be substantial.
117340040
Dimuon backgrounds to thermal signatures in heavy ion collisions