Universal centrality and collision energy trends for nu(2) measurements from 2D angular correlations

作者：Kettler David^*

来源：European Physical Journal C, 2009, 62(1): 175-181.

DOI：10.1140/epjc/s10052-009-1003-5

We have measured the p(t)-integrated quadrupole component of two-particle azimuth correlations (related to quantity nu(2), denoted in this case by nu(2){2D}) via two-dimensional (2D) angular autocorrelations on (eta, phi) for unidentified hadrons in Au-Au collisions at 62 and 200 GeV. The 2D autocorrelation provides a method to remove non-quadrupole contributions to nu(2) (conventionally termed "non-flow") under the assumption that such processes produce significant dependence on pair-wise relative eta within the detector acceptance. We hypothesize, based on empirical observations, that non-quadrupole contributions are dominated by minijets or minimum-bias jets. Using the optical Glauber eccentricity model for initial-state geometry we find simple and accurate universal energy and centrality trends for the quadrupole component. Centrality trends are determined only by the initial state (impact parameter b and center-of-mass energy root s(NN)). There is no apparent dependence on evolving system dynamics (e. g., equation of state or number of secondary collisions). Our measurements of the quadrupole and non-quadrupole components have implications for the contributions to nu(2). They suggest that the main source of the difference between nu(2){2} and nu(2){4} (or nu(2){2D}) is measured properties of minijets.

• 出版日期2009-7