Kaon interferometry as signal for the QCD phase transition at RHIC

Abstract

Pion and kaon correlations in relativistic nuclear collisions are studied in the framework of boost-invariant, cylindrically symmetric hydrodynamics. It is investigated how the inverse widths, R out , R side , of the two-particle correlation functions in out-and side-direction depend on the average transverse momentum K ⊥ of the particle pair, the initial energy density ǫ 0 , and the equation of state of the system. The QCD transition leads to a time delay in the expansion of the system and consequently to an enhancement of the ratio R out /R side . This time-delay signal is found to be particularly strong for large average transverse momenta K ⊥ ∼ 1 GeV and initial energy densities accessible at RHIC, ǫ 0 ∼ 10 − 20 GeV fm −3 . Neutral kaon pair correlation functions, which are not influenced by final state Coulomb effects and less contaminated by resonance decays than pion correlation functions, seem to be the ideal tool to detect this collective time-delay signature of the QCD transition. † Supported by DFG, BMBF, GSI, and DOE.

Fitted Hanbury-Brown–Twiss radii versus space-time variances in flow-dominated models

“…III A and III B, restricting the k sums in Eqs. (15), (16), (24), and (25) to include only those data points where all three q components have magnitudes less than q max [27]. Thus, we will not calculate unique HBT radii, but a finite range for each fit parameter.…”

“…Most (but not all [11][12][13]15,16]) hydrodynamic predictions of HBT radius parameters have been based on calculations of the spatial RMS variances from the hydrodynamically generated emission function, using Eqs. (6) [9,10].…”

“…One such study [16] compared space-time variances with Gaussian radii extracted from moments of the calculated correlation function. For identical kaon correlations, the radii extracted were almost independent of the method used.…”

Boson interferometry in high-energy physics

“…To avoid this complication, in [161] it was proposed to consider kaons at large k ⊥ . However even this…”

Space-time analysis: HBT at SPS and RHIC

“…The expression for the one-particle and two-particle spectra (1) and (2) in terms of the emission function S(x, K) form the starting point for various different approaches: i) In hydrodynamical simulations of heavy ion collisions [13,14], they specify the integrations over the freeze-out hypersurface. ii) For event generator studies, a discretized formulation exists [12].…”