Long range rapidity correlations and jet production in high energy nuclear collisions

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<pₜ<4 GeV/c).