Symmetric correlations as seen at RHIC

Abstract

We analyze the forward-backward multiplicity correlation coefficient as measured by STAR. We show that in the most central Au+Au collisions bins located symmetrically around η= 0 with large separation in pseudorapidity are more strongly correlated than bins located asymmetrically with smaller separation. In proton-proton collisions the opposite effect is observed. It suggests a qualitatively different behavior of the two-particle correlation as a function of pseudorapidity sum in p+p and Au+Au collisions.

7 pages; argument with the STAR ZDC added, more accurate calculation performed, conclusions unchanged; new section 4 with comments, to appear in Phys. Rev. C Rapid Comm