The "shoulder" and the "ridge" in PHENIX

Comparison of two-particle correlations in heavy-ion collisions with measurements in proton collisions shows strong modification of the correlation shape and particle yields. Two new structures are created; both extended in Δη, one centered at Δ = 0 ('ridge') and the other occurring at Δ π ± 1.1 ('shoulder'). In these proceedings, we describe the measurements of these structures that show consistency with a scenario of parton–medium interaction and response. We discuss a new analysis with improved resolution in selections on the angle of trigger particles relative to the reaction plane. New measurements of the centrality and pT dependences of the structures raise the possibility that the same production mechanism may give rise to both phenomena