Three-dimensional Kaon Source Imaging from STAR Experiment at RHIC

Three-dimensional (3-D) source imaging techniques in conjunction with detailed model comparisons have shown the viability of disentangling the spatio-temporal information contained in two-pion interferometric measurements from ultra-relativistic heavy ion collisions. This has led to the observation of non-Gaussian tails in the 3-D pion source function and the extraction of finite pion emission duration at RHIC energies [1]. The STAR Collaboration has recently also extracted the 3-D kaon source function from a high statistics two-kaon interferometric measurement from Au+Au collisions at √ sNN = 200 GeV. Such measurement offers a window into the fireball freeze-out dynamics with a much cleaner probe with smaller resonance decay contributions than for the pion case. The extracted kaon source function is found to have an essentially ellipsoidal shape. The source function can be adequately reproduced by the Therminator event generator[2] with a fireball lifetime τ0 = 8 fm/c and instantaneous kaon emission. Kaon emission is deemed to occur over a different time-scale and from a different freeze-out hypersurface than pion emission, implying a changing dynamics during the evolution of the fireball.