We present the first excitation function of pi(-) intensity interferometry at Alternating Gradient Synchrotron (AGS) energies (2-8 A GeV). The sensitivity of the multidimensional correlation ...functions to the geometry and dynamics of the pion-emitting system provides a stringent test of transport models of heavy ion collisions. Detailed comparisons with a realistic transport model, both with and without an explicit nuclear mean field, suggest that the beam energy evolution in the reaction dynamics is different in the model than in the data. A significantly increased pi(-) emission time scale, which has been suggested as a signal of the onset of the transition to quark-gluon plasma, is not observed.
We calculate the kaon-interferometry radius parameters for high-energy heavy-ion collisions, assuming a first-order phase transition from a thermalized quark-gluon plasma (QGP) to a gas of hadrons. ...At high transverse momenta K(T) approximately 1 GeV/c direct emission from the phase boundary becomes important; the emission duration signal, i.e., the R(out)/R(side) ratio, and its sensitivity to T(c) (and thus to the latent heat) are enlarged. The QGP+hadronic rescattering transport model calculations do not yield unusually large radii (R(i) < or = 9 fm). Finite-momentum-resolution effects have a strong impact on the extracted interferometry parameters ( R(i) and lambda), as well as on the ratio R(out)/R(side).
Azimuthal anisotropy (v(2)) and two-particle angular correlations of high p(T) charged hadrons have been measured in Au+Au collisions at sqrts(NN)=130 GeV for transverse momenta up to 6 GeV/c, where ...hard processes are expected to contribute significantly. The two-particle angular correlations exhibit elliptic flow and a structure suggestive of fragmentation of high p(T) partons. The monotonic rise of v(2)(p(T)) for p(T)<2 GeV/c is consistent with collective hydrodynamical flow calculations. At p(T)>3 GeV/c, a saturation of v(2) is observed which persists up to p(T)=6 GeV/c.
Using the large acceptance Time Projection Chamber of experiment E895 at Brookhaven, measurements of collective sideward flow in Au+Au collisions at beam energies of 2A, 4A, 6A, and 8A GeV are ...presented in the form of in-plane transverse momentum <p(x)> and the first Fourier coefficient of azimuthal anisotropy v(1). These measurements indicate a smooth variation of sideward flow as a function of beam energy. The data are compared with four nuclear transport models which have an orientation towards this energy range. All four exhibit some qualitative trends similar to those found in the data, although none show a consistent pattern of agreement within experimental uncertainties.
We report a particle source imaging analysis based on two-pion correlations in high multiplicity Au+Au collisions at beam energies between 2A and 8A GeV. We apply the imaging technique introduced by ...Brown and Danielewicz, which allows a model-independent extraction of source functions with useful accuracy out to relative pion separations of about 20 fm. The extracted source functions have Gaussian shapes. Values of source functions at zero separation are almost constant across the energy range under study. Imaging results are found to be consistent with conventional source parameters obtained from a multidimensional Hanburg-Brown-Twiss analysis.
PDF
