Transverse-mass dependence of two-pion correlations in Au+Au collisions at square root[s(NN)] = 130 GeV

Evidence for a long-range component in the pion emission source in Au+Au collisions at sqrt sNN=200 GeV

Emission source functions are extracted from correlation functions constructed from charged pions produced at midrapidity in Au+Au collisions at sqrt[s(NN)]=200 GeV. The source parameters extracted from these functions at low k(T) give first indications of a long tail for the pion emission source. The source extension cannot be explained solely by simple kinematic considerations. The possible role of a halo of secondary pions from resonance emissions is explored.

Deuteron and antideuteron production in Au+Au collisions at square root of s(NN)=200 GeV

The production of deuterons and antideuterons in the transverse momentum range 1.1<p(T)<4.3 GeV/c at midrapidity in Au+Au collisions at square root of s(NN)=200 GeV has been studied by the PHENIX experiment at RHIC. A coalescence analysis, comparing the deuteron and antideuteron spectra with that of proton and antiproton, has been performed. The coalescence probability is equal for both deuterons and antideuterons and it increases as a function of p(T), which is consistent with an expanding collision zone. Comparing (anti)proton yields, p /p=0.73+/-0.01, with (anti)deuteron yields, d /d=0.47+/-0.03, we estimate that n /n=0.64+/-0.04. The nucleon phase space density is estimated from the coalescence measurement.

Quantum opacity, the RHIC Hanbury Brown-Twiss puzzle, and the chiral phase transition

We present a relativistic quantum-mechanical treatment of opacity and refractive effects that allows reproduction of observables measured in two-pion Hanbury Brown-Twiss (HBT) interferometry and pion spectra at RHIC. The inferred emission duration is substantial. The results are consistent with the emission of pions from a system that has a restored chiral symmetry.

Fluctuations of the initial conditions and the continuous emission in the hydrodynamical description of two-pion interferometry

Within the hydrodynamical approach, we study the Bose-Einstein correlation of identical pions by taking into account both event-by-event fluctuating initial conditions and continuous pion emission during the whole development of the hot and dense matter formed in high-energy collisions. Important deviations occur, compared to the usual hydrocalculations with smooth initial conditions and a sudden freeze-out on a well defined hypersurface. Comparison with data at the BNL Relativistic Heavy Ion Collider (RHIC) shows that, despite the rather rough approximation we used here, this description can account for the m(T) dependence of R(L) and R(s), and produces a significant improvement for R(o) with respect to the usual version.

Bose-Einstein correlations of charged pion pairs in Au + Au collisions at square root sNN = 200 GeV

Bose-Einstein correlations of identically charged pion pairs were measured by the PHENIX experiment at midrapidity in Au + Au collisions at square root s(NN)=200 GeV. The Bertsch-Pratt radius parameters were determined as a function of the transverse momentum of the pair and as a function of the centrality of the collision. Using the standard core-halo partial Coulomb fits, and a new parametrization which constrains the Coulomb fraction as determined from the unlike-sign pion correlation, the ratio R(out)/R(side) is within 0.8-1.1 for 0.25< <k(T)> <1.2 GeV/c. The centrality dependence of all radii is well described by a linear scaling in N(1/3)(part), and R(out)/R(side) for <k(T)> approximately 0.45 GeV/c is approximately constant at unity as a function of centrality.

Differential freeze-out and pion interferometry at RHIC from covariant transport theory

Puzzling discrepancies between recent pion interferometry data on Au+Au reactions at square root of s=30 and 200 AGeV from RHIC and predictions based on ideal hydrodynamics are analyzed in terms of covariant parton transport theory. The discrepancies in the R(out)/R(side) ratio are significantly reduced when the finite opacity of the gluon plasma is taken into account. However, the magnitude of the radii is not well accounted for.

Hadronization in heavy-ion collisions: recombination and fragmentation of partons

We argue that the emission of hadrons with transverse momentum up to about 5 GeV/c in central relativistic heavy ion collisions is dominated by recombination, rather than fragmentation of partons. This mechanism provides a natural explanation for the observed constant baryon-to-meson ratio of about one and the apparent lack of a nuclear suppression of the baryon yield in this momentum range. Fragmentation becomes dominant at higher transverse momentum, but the transition point is delayed by the energy loss of fast partons in dense matter.

Partonic effects on pion interferometry at the relativistic heavy-ion collider

Using a multiphase transport model that includes both initial partonic and final hadronic interactions, we study the pion interferometry at the Relativistic Heavy-Ion Collider. We find that the two-pion correlation function is sensitive to the magnitude of the parton-scattering cross section, which controls the parton density at which the transition from the partonic to hadronic matter occurs. Also, the emission source of pions is non-Gaussian, leading to source radii that can be more than twice larger than the radius parameters extracted from a Gaussian fit to the correlation function.