Imaging of Sources in Heavy-Ion Reactions

Imaging of sources from data within the intensity interferometry is discussed. In the two-pion case, the relative pion source function may be determined through the Fourier transformation of the correlation function. In the proton-proton case, the discretized source function may be fitted to the correlation data.Comment: 12 pages, 3 postscript figures, accepted Physics Letters

Implications of the unusual structure in the pp correlation from Pb+Pb collisions at 158 AGeV

The recent NA49 measurement of two-proton correlation function shows an interesting and unexpected structure at large relative momentum. Applying source imaging techniques to the measurement, we find an unusually steep drop-off in the two-proton source function. We show that the steep drop-off is due to the structure in the correlation and the drop-off cannot be explained using conventional correlation analysis. We suggest possible physics reasons for the unusual source function.Comment: 6 pages, 3 eps figures, uses RevTex.sty. To appear in Physics Letters B. Updated 10/26/99 with cleaner figures and added discussions of analysis done in nucl-ex/9905001 and of imagin

Correlations within the Non-Equilibrium Green's Function Method

Non-equilibrium Green's Function (NGF) method is a powerful tool for studying the evolution of quantum many-body systems. Different types of correlations can be systematically incorporated within the formalism. The time evolution of the single-particle Green's functions is described in terms of the Kadanoff-Baym equations. The current work initially focuses on introducing the correlations within infinite nuclear matter in one dimension and then in a finite system in the NGF approach. Starting from the harmonic oscillator Hamiltonian, by switching on adiabatically the mean-field and correlations simultaneously, a correlated state with ground-state characteristics is arrived at within the NGF method. Furthermore the use of cooling to for improving the adiabatic switching is explored.Comment: Contribution to Proc. 5th Conference on Nuclei and Mesoscopic Physics, E Lansing, 6-10 March 2017; 9 pages, 8 figure

Probing the isospin dependence of the in-medium nucleon-nucleon cross sections with radioactive beams

Within a transport model we search for potential probes of the isospin dependence of the in-medium nucleon-nucleon (NN) cross sections. Traditional measures of the nuclear stopping power are found sensitive to the magnitude but they are ambiguous for determining the isospin dependence of the in-medium NN cross sections. It is shown that isospin tracers, such as the neutron/proton ratio of free nucleons, at backward rapidities/angles in nuclear reactions induced by radioactive beams in inverse kinematics is a sensitive probe of the isospin dependence of the in-medium NN cross sections. At forward rapidities/angles, on the other hand, they are more sensitive to the density dependence of the symmetry energy. Measurements of the rapidity/angular dependence of the isospin transport in nuclear reactions will enable a better understanding of the isospin dependence of in-medium nuclear effective interactions.Comment: 19 pages including 7 figures, submitted to Phys. Rev.

Particle production in quantum transport theories

The particle production in the intermediate energy heavy ion collisions is discussed in the framework of the nonequilibrium Green's functions formalism. The evolution equations of the Green's functions for fermions allows for the discussion of the off-shell fermion propagator and of the large momentum component in the initial state. For the case of a homogeneous system numerical calculations of the meson production rate are performed and compared with the semiclassical production rate.Comment: 45 pages, figures included, uses FEYNMAN macro

Towards the 3D-Imaging of Sources

Geometric details of a nuclear reaction zone, at the time of particle emission, can be restored from low relative-velocity particle-correlations, following imaging. Some of the source details get erased and are a potential cause of problems in the imaging, in the form of instabilities. These can be coped with by following the method of discretized optimization for the restored sources. So far it has been possible to produce 1-dimensional emission source images, corresponding to the reactions averaged over all possible spatial directions. Currently, efforts are in progress to restore angular details.Comment: Talk given at the Int. Workshop on Hot and Dense Matter in Relativistic Heavy Ion Collisions, March 24-27, 2004, Budapest; 10 pages, 6 figure

Has the QCD Critical Point been Signaled by Observations at RHIC ?

The shear viscosity to entropy ratio ($\eta/s$) is estimated for the hot and dense QCD matter created in Au+Au collisions at RHIC ($\sqrt{s_{NN}}=200$ GeV). A very low value is found $\eta/s \sim 0.1$, which is close to the conjectured lower bound ($1/4\pi$). It is argued that such a low value is indicative of thermodynamic trajectories for the decaying matter which lie close to the QCD critical end point.Comment: 4 pages, 3 figures. Revised version, accepted for publication in PR

Dynamical Manifestation of the Goldstone Phenomenon at 1-loop

We have calculated the damping rate $\Gamma (|{\bf k}|)$ for classical on-shell Goldstone modes of the O(2) symmetric scalar fields propagating in a thermal medium of the broken symmetry phase taking into account the effect of the explicit symmetry breaking. The result of the one-loop analysis can be expanded around $\Gamma (0)$, which depends non-analytically on the parameter of the explicit symmetry breaking, h. $\Gamma (0)$ vanishes when $h\to 0$, demonstrating in this way the absence of the restoring force, when the equilibrium direction of the symmetry breaking is modulated homogeneously.Comment: 8 pages, Late