Abstract
The PHENIX experiment has measured the production of s in collisions at 200 GeV. The new data offer a fourfold increase in recorded luminosity, providing higher precision and a larger reach in transverse momentum, , to 20 GeV/. The production ratio of is , constant with and collision centrality. The observed ratio is consistent with earlier measurements, as well as with the and values. are suppressed by a factor of 5, as in earlier findings. However, with the improved statistical precision a small but significant rise of the nuclear modification factor vs , with a slope of 0.0106 (Gev/), is discernible in central collisions. A phenomenological extraction of the average fractional parton energy loss shows a decrease with increasing . To study the path-length dependence of suppression, the yield is measured at different angles with respect to the event plane; a strong azimuthal dependence of the is observed. The data are compared to theoretical models of parton energy loss as a function of the path length in the medium. Models based on perturbative quantum chromodynamics are insufficient to describe the data, while a hybrid model utilizing pQCD for the hard interactions and anti-de-Sitter space/conformal field theory (AdS/CFT) for the soft interactions is consistent with the data.
15 More- Received 12 August 2012
DOI:https://doi.org/10.1103/PhysRevC.87.034911
©2013 American Physical Society