Studying the jet medium interaction by two particle Δ η–Δ ϕ correlations

Abstract

We present two-dimensional Δ η–Δ ϕ inclusive photon-charged hadron correlations measured by the PHENIX experiment. Jet-like correlations are modified in central Au + Au collisions compared to p + p collisions, in both the trigger jet and opposing jet. The trigger jet is elongated in pseudo-rapidity (the “ridge”), while the opposing jet shows a double peak structure (“head” and “shoulder”). We decompose the structures by fitting the Δ η and Δ ϕ correlations to disentangle components from the medium, the punch-through and the trigger jets. The ridge exists for associated particle p T below 3 GeV / c ; it is broad in rapidity and narrow in Δ ϕ. The away side correlated particle yield is enhanced in central collisions. The yield of the ridge closely resembles the shoulder in the centrality dependence of particle yield and spectra.