Abstract
The STAR Collaboration at the Relativistic Heavy Ion Collider presents a systematic study of high-transverse-momentum charged-di-hadron correlations at small azimuthal pair separation ΔΦ in d+Au and central Au+Au collisions at sNN=200 GeV. Significant correlated yield for pairs with large longitudinal separation Δη is observed in central Au+Au collisions, in contrast to d+Au collisions. The associated yield distribution in Δη×ΔΦ can be decomposed into a narrow jet-like peak at small angular separation which has a similar shape to that found in d+Au collisions, and a component that is narrow in ΔΦ and depends only weakly on Δη, the "ridge." Using two systematically independent determinations of the background normalization and shape, finite ridge yield is found to persist for trigger pt>6 GeV/c, indicating that it is correlated with jet production. The transverse-momentum spectrum of hadrons comprising the ridge is found to be similar to that of bulk particle production in the measured range (2