Dynamic buckling and fragmentation in brittle rods

We present experiments on the dynamic buckling and fragmentation of slender rods axially impacted by a projectile. By combining the results of Saint-Venant and elastic beam theory, we derive a preferred wavelength lambda for the buckling instability, and experimentally verify the resulting scaling law for a range of materials including teflon, dry pasta, glass, and steel. For brittle materials, buckling leads to the fragmentation of the rod. Measured fragment length distributions show two clear peaks near lambda/2 and lambda/4. The non-monotonic nature of the distributions reflect the influence of the deterministic buckling process on the more random fragmentation processes.Comment: 4 pages, 5 figures, submitted to Physical Review Letter

Quantum corrections for pion correlations involving resonance decays

A method is presented to include quantum corrections into the calculation of two-pion correlations for the case where particles originate from resonance decays. The technique uses classical information regarding the space-time points at which resonances are created. By evaluating a simple thermal model, the method is compared to semiclassical techniques that assume exponential decaying resonances moving along classical trajectories. Significant improvements are noted when the resonance widths are broad as compared to the temperature.Comment: 9 pages, 4 figure

Optimized Discretization of Sources Imaged in Heavy-Ion Reactions

We develop the new method of optimized discretization for imaging the relative source from two particle correlation functions. In this method, the source resolution depends on the relative particle separation and is adjusted to available data and their errors. We test the method by restoring assumed pp sources and then apply the method to pp and IMF data. In reactions below 100 MeV/nucleon, significant portions of the sources extend to large distances (r > 20 fm). The results from the imaging show the inadequacy of common Gaussian source-parametrizations. We establish a simple relation between the height of the pp correlation function and the source value at short distances, and between the height and the proton freeze-out phase-space density.Comment: 36 pages (inc. 9 figures), RevTeX, uses epsf.sty. Submitted to Phys. Rev.

Imaging Sources with Fast and Slow Emission Components

We investigate two-proton correlation functions for reactions in which fast dynamical and slow evaporative proton emission are both present. In such cases, the width of the correlation peak provides the most reliable information about the source size of the fast dynamical component. The maximum of the correlation function is sensitive to the relative yields from the slow and fast emission components. Numerically inverting the correlation function allows one to accurately disentangle fast dynamical from slow evaporative emission and extract details of the shape of the two-proton source.Comment: 13 pages, 4 figure

Probing Transport Theories via Two-Proton Source Imaging

Imaging technique is applied to two-proton correlation functions to extract quantitative information about the space-time properties of the emitting source and about the fraction of protons that can be attributed to fast emission mechanisms. These new analysis techniques resolve important ambiguities that bedeviled prior comparisons between measured correlation functions and those calculated by transport theory. Quantitative comparisons to transport theory are presented here. The results of the present analysis differ from those reported previously for the same reaction systems. The shape of the two-proton emitting sources are strongly sensitive to the details about the in-medium nucleon-nucleon cross sections and their density dependence.Comment: 23 pages, 11 figures. Figures are in GIF format. If you need postscript format, please contact: [email protected]

Deuteron life-time in hot and dense nuclear matter near equilibrium

We consider deuteron formation in hot and dense nuclear matter close to equilibrium and evaluate the life-time of the deuteron fluctuations within the linear response theory. To this end we derive a generalized linear Boltzmann equation where the collision integral is related to equilibrium correlation functions. In this framework we then utilize finite temperature Green functions to evaluate the collision integrals. The elementary reaction cross section is evaluated within the Faddeev approach that is suitably modified to reflect the properties of the surrounding hot and dense matter.Comment: 15 pages, 5 figure

Studies in the statistical and thermal properties of hadronic matter under some extreme conditions

The thermal and statistical properties of hadronic matter under some extreme conditions are investigated using an exactly solvable canonical ensemble model. A unified model describing both the fragmentation of nuclei and the thermal properties of hadronic matter is developed. Simple expressions are obtained for quantities such as the hadronic equation of state, specific heat, compressibility, entropy, and excitation energy as a function of temperature and density. These expressions encompass the fermionic aspect of nucleons, such as degeneracy pressure and Fermi energy at low temperatures and the ideal gas laws at high temperatures and low density. Expressions are developed which connect these two extremes with behavior that resembles an ideal Bose gas with its associated Bose condensation. In the thermodynamic limit, an infinite cluster exists below a certain critical condition in a manner similar to the sudden appearance of the infinite cluster in percolation theory. The importance of multiplicity fluctuations is discussed and some recent data from the EOS collaboration on critical point behavior of nuclei can be accounted for using simple expressions obtained from the model.Comment: 22 pages, revtex, includes 6 figures, submitted to Phys. Rev.

Quantum-Statistical Correlations and Single Particle Distributions for Slowly Expanding Systems with Temperature Profile

Competition among particle evaporation, temperature gradient and flow is investigated in a phenomenological manner, based on a simultaneous analysis of quantum statistical correlations and momentum distributions for a non-relativistic, spherically symmetric, three-dimensionally expanding, finite source. The parameters of the model emission function are constrained by fits to neutron and proton momentum distributions and correlation functions in intermediate energy heavy-ion collisions. The temperature gradient is related to the momentum dependence of the radius parameters of the two-particle correlation function, as well as to the momentum-dependent temperature parameter of the single particle spectrum, while a long duration of particle evaporation is found to be responsible for the low relative momentum behavior of the two-particle correlations.Comment: 20 pages + 5 ps figures, ReVTeX, uses psfig.sty, the description is extended to include final state interactions, phenomenological evaporation and to fit intermediate energy heavy ion proton and neutron spectrum and correlation dat