Resonances and Correlations in heavy ion collisions

Results of resonance production from RHIC at $sqrt {s_{NN} } = 200$ GeV and SPS at $sqrt {s_{NN} } = 17$ GeV are presented and discussed in context with a possible hadronic interaction phase after chemical freeze-out in a heavy ion collision. Momentum spectra and yield may change due to rescattering and regeneration of hadronic decaying resonances. We compare the decays of resonances into leptonic and hadronic channels in order to discuss the impact of a the possible medium modifications on the resonance and their decay products. Microscopic model calculations predicts that high momentum resonances are almost unaffected by the hadronic medium. This raises the idea of using high transverse momentum selection criteria in order to extract resonances created at an early stage of a heavy ion collision.