Abstract
Measurements of two-particle correlations on angular difference variables (pseudorapidity) and (azimuth) are presented for all primary charged hadrons with transverse momentum GeV/ and from Au-Au collisions at GeV. Large-amplitude correlations are observed over a broad range in relative angles where distinct structures appear on the same-side and away-side (i.e., relative azimuth less than or greater than ). The principal correlation structures include that associated with elliptic flow plus a strong, same-side peak. It is hypothesized that the latter results from correlated hadrons associated with semi-hard parton scattering in the early stage of the heavy-ion collision which produces a jet-like correlation peak at small relative angles. The width of the jet-like peak on increases by a factor 2.3 from peripheral to central collisions, suggesting strong coupling of semi-hard scattered partons to a longitudinally-expanding medium. The new methods of jet analysis introduced here provide access to scattered partons at low transverse momentum well below the kinematic range where perturbative quantum chromodynamics and standard fragmentation models are applicable.
- Received 10 April 2006
DOI:https://doi.org/10.1103/PhysRevC.73.064907
©2006 American Physical Society