Pion-Kaon correlations in central Au+Au collisions at $\sqrt{s_{NN}}=130$ GeV

Pion-kaon correlation functions are constructed from central Au+Au data taken at $\sqrt{s_{NN}}=130$ GeV. The results suggest that pions and kaons are not emitted at the same average space-time point. Space-momentum correlations, i.e. transverse flow, lead to a space-time emission asymmetry of pions and kaons that is consistent with the data. This result provides new independent evidence that the system created at RHIC undergoes a collective transverse expansion.