16059029
Coalescence, percolation and nuclear multifragmentation
Abstract We show that the coalescence model for fragment formation leads to an approximate site percolation model. Features characteristic of a percolation model also appear in microscopic models of disassembly.
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
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.
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.
118646248
Predictions from High Scale Mixing Unification Hypothesis
We investigate the renormalization group evolution of masses and mixing angles of Majorana neutrinos under the ``high scale mixing unification'' hypothesis. Assuming the unification of quark-lepton mixing angles at a high scale, we show that all the experimentally observed neutrino oscillation parameters can be obtained, within the $3\text{\ensuremath{-}}\ensuremath{\sigma}$ range, through the running of corresponding renormalization group equations provided neutrinos have the same charge parity and are quasidegenerate. One of the novel results of our analysis is that ${\ensuremath{\theta}}_{23}$ turns out to be nonmaximal and lies in the second octant. Furthermore, we derive new constraints on the allowed parameter space for the unification scale, supersymmetry breaking scale and $\mathrm{tan}\ensuremath{\beta}$, for which the high scale mixing unification hypothesis works.
16462004
DIMENSIONAL REDUCTION AND SCREENING MASSES IN PURE GAUGE THEORIES AT FINITE TEMPERATURE
Abstract We studied screening masses in the equilibrium thermodynamics of SU (2) and SU (3) pure gauge theories on the lattice. At a temperature of 2 T c we found strong evidence for dimensional reduction in the non-perturbative spectrum of screening masses. Mass ratios in the high-temperature SU (3) theory are consistent with those in the pure gauge theory in three dimensions. At the first-order SU (3) phase transition we report the first measurement of the true scalar screening mass.
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.
121431296
Optical model calculation of exciton decay rates
The decay rate of an exciton is calculated using the imaginary part of both the phenomenological optical potential of Becchetti and Greenless and the microscopic potential of Jeukenne et al., The decay rate thus calculated is found to be about the same for proton- and neutron-induced reactions and weakly sensitive to mass number. Kalbach's two body matrix element, obtained from the analysis of precompound reactions using the Williams exciton model, also leads to a decay rate in agreement with the phenomenological potential estimate. However, the exciton model of Gadioli et al. is inconsistent with optical model estimates. Further, remarks are made on the concept of a mean free path in finite nuclear matter.
120228440
Regularization of fermion loops in gauge models
Fermion loops in gauge models with ${\ensuremath{\gamma}}_{5}$ couplings cannot be regularized in a gauge-invariant manner either by the method of auxiliary fields or by dimensional continuation. It is shown that in the absence of a gauge-invariant regularization procedure, the method of auxiliary fields can be employed in such a way that non-gauge-invariance is confined to the renormalization constants. It is thus possible to obtain gauge-invariant renormalized results as well as resolve anomalies without the use of Ward's identities. Explicit calculations are carried out for the self-energy and triangle diagrams with fermion loops in the Appelquist-Quinn model. The present treatment is also compared with naive dimensional regularization for the ${\ensuremath{\gamma}}_{5}$ couplings.