N. N. Ajitanand

Elliptic flow: Transition from out-of-plane to in-plane emission in Au + Au collisions

We have measured the proton elliptic flow excitation function for the Au + Au system spanning the beam energy range 2 -- 8 AGeV. The excitation function shows a transition from negative to positive elliptic flow at a beam energy,

J/psi production in Au-Au collisions at root s(NN)=200 GeV

E_{tr} sim

Azimuthal dependence of pion interferometry at the AGS

4 AGeV. Detailed comparisons with calculations from a relativistic Boltzmann-equation are presented. The comparisons suggest a softening of the nuclear equation of state (EOS) from a stiff form (K sim 380 MeV) at low beam energies (E_{Beam} le 2 AGeV) to a softer form (K sim 210 MeV) at higher energies (E_{Beam} ge

Transverse momentum dependence of η meson suppression in Au+Au collisions at √sNN=200 GeV

4 AGeV) where the calculated baryon density

Comparison of source images for protons, pi-'s, and lambda's in 6A GeV Au+Au collisions.

rho sim 4 rho_0

Centrality and momentum-selected elliptic flow: Tighter constraints for the nuclear equation of state

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NEUTRAL STRANGE PARTICLE PRODUCTION AND FLOW AT AGS ENERGIES

First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The yield of J/Psis measured in the PHENIX experiment via electron-positron decay pairs at mid-rapidity for Au-Au reactions at sqrt(s_NN) = 200 GeV are analyzed as a function of collision centrality. For this analysis we have studied 49.3 million minimum bias Au-Au reactions. We present the J/Psi invariant yield dN/dy for peripheral and mid-central reactions. For the most central collisions where we observe no signal above background, we quote 90% confidence level upper limits. We compare these results with our J/Psi measurement from proton-proton reactions at the same energy. We find that our measurements are not consistent with models that predict strong enhancement relative to binary collision scaling.

Collective flow and particle spectra in relativistic heavy ion collisions

Abstract Two-pion correlation functions, measured as a function of azimuthal emission angle with respect to the reaction plane, provide novel information on the anisotropic shape and orientation of the pion-emitting zone formed in heavy ion collisions. We present the first experimental determination of this information, for semi-central Au + Au collisions at 2–6xa0 A GeV. The source extension perpendicular to the reaction plane is greater than the extension in the plane, and tilt of the pion source in coordinate space is found to be opposite its tilt in momentum space.

MODGAN: An efficient Monte Carlo code for long chains of evaporative emission

New measurements by the PHENIX experiment at the Relativistic Heavy Ion Collider for eta production at midrapidity as a function of transverse momentum (p{sub T}) and collision centrality in sq root(s{sub NN})=200 GeV Au+Au and p+p collisions are presented. They indicate nuclear modification factors (R{sub AA}) which are similar in both magnitude and trend to those found in earlier pi{sup 0} measurements. Linear fits to R{sub AA} as a function of p{sub T} in 5-20 GeV/c show that the slope is consistent with zero within two standard deviations at all centralities, although a slow rise cannot be excluded. Having different statistical and systematic uncertainties, the pi{sup 0} and eta measurements are complementary at high p{sub T}; thus, along with the extended p{sub T} range of these data they can provide additional constraints for theoretical modeling and the extraction of transport properties.

A ΔE gas ionization chamber for fission fragments

Source images are extracted from two-particle correlations constructed from strange and nonstrange hadrons produced in 6A GeV Au+Au collisions. Very different source images result from pp vs p Lambda vs pi(-)pi(-) correlations. Scaling by transverse mass can describe the apparent source size ratio for p/pi(-) but not for Lambda/pi(-) or Lambda/p. These observations suggest important differences in the space-time emission histories for protons, pions, and neutral strange baryons produced in the same events.