PHENIX study of dihadron Δη correlation in Au + Au collision at ?{sNN } \sqrt {s_{NN} } = 200 GeV: the ridge

We show the recent study of the ridge phenomena by PHENIX Collaboration over a broad transverse momentum (p _T ) range. Properties of the ridge are extracted in terms of its shape in Δϕ and Δη, and its yield. These properties are found to be similar to the away-side modification in the same p _T range, suggesting a related modification mechanisms in both the near- and away-side.