Freeze-out dynamics via charged kaon femtoscopy in √s[subscript NN] = 200 GeV central Au + Au collisions

Abstract

We present measurements of three-dimensional correlation functions of like-sign, low-transverse-momentum kaon pairs from √s[subscript NN] = 200 GeV Au + Au collisions. A Cartesian surface-spherical harmonic decomposition technique was used to extract the kaon source function. The latter was found to have a three-dimensional Gaussian shape and can be adequately reproduced by Therminator event-generator simulations with resonance contributions taken into account. Compared to the pion one, the kaon source function is generally narrower and does not have the long tail along the pair transverse momentum direction. The kaon Gaussian radii display a monotonic decrease with increasing transverse mass m[subscript T] over the interval of 0.55 ≤ m[subscript T] ≤ 1.15 GeV/c[superscript 2]. While the kaon radii are adequately described by the m[subscript T]-scaling in the outward and sideward directions, in the longitudinal direction the lowest m[subscript T] value exceeds the expectations from a pure hydrodynamical model prediction.