Abstract

STAR measurements of dihadron azimuthal correlations (Lambda phi) are reported in midcentral (20-60%) Au + Au collisions at v root sNN = 200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane, phi(s) = | phi(1) -psi(EP)|. The elliptic (v(2)), triangular (v(3)), and quadratic (v(4)) flow harmonic backgrounds are subtracted using the zero yield at mini + Au collisions. It is found that a finite near-side (| Delta phi | pi/2) long-range pseudorapidity correlation (ridge) is present in the in-plane direction (phi(s) similar to 0). The away-side (| Delta phi | > pi/2) correlation shows a modification from d+ Au data, varying with fs. The modification may be a consequence of path-length-dependent jet quenching and may lead to a better understanding of high-density QCD.