Abstract

Measurements of two-particle correlations on angular difference variables eta(1)-eta(2) (pseudorapidity) and phi(1)-phi(2) (azimuth) are presented for all primary charged hadrons with transverse momentum 0.15 = p(t)= 2 GeV/c and vertical bar eta vertical bar = 1.3 from Au-Au collisions at root s(NN)=130 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 pi/2 or greater than pi/2). 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 eta(1)-eta(2) 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.