Freeze-out Dynamics via Charged Kaon Femtoscopy in sqrt(sNN)=200 GeV Central Au+Au Collisions

TL;DR

This study measures three-dimensional correlation functions of low transverse momentum charged kaon pairs in high-energy gold-gold collisions, revealing source shape, size, and dynamics consistent with some hydrodynamic models but with notable deviations at low transverse mass.

Contribution

It introduces a novel application of Cartesian surface-spherical harmonic decomposition to analyze kaon source functions in heavy-ion collisions, providing new insights into freeze-out dynamics.

Findings

Kaon source function is Gaussian and narrower than pion source.

Kaon radii decrease monotonically with increasing transverse mass.

Longitudinal radii at low m_T exceed hydrodynamic model predictions.

Abstract

We present measurements of three-dimensional correlation functions of like-sign low transverse momentum kaon pairs from sqrt(sNN)=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_T over the interval of 0.55<=m_T<=1.15 GeV/c^2. While the kaon radii are adequately described by the m_T-scaling in the outward and sideward directions, in the longitudinal direction the lowest m_T value exceeds the expectations from a pure hydrodynamical model prediction.