Azimuthal Dependence of Pion Interferometry at the AGS
  Two-pion correlation functions, measured as a function of azimuthal emission angle with respect to the reaction plane, provide novel information on the anisotropic shape and orientation of the pion-emitting zone formed in heavy ion collisions. We present the first experimental determination of this information, for semi-central Au+Au collisions at 2-6 AGeV. The source extension perpendicular to the reaction plane is greater than the extension in the plane, and tilt of the pion source in coordinate space is found to be opposite its tilt in momentum space. 
E895 Collaboration: M. A. Lisa, N. N. Ajitanand, J. M. Alexander, M.   Anderson, D. Best, F. P. Brady, T. Case, W. Caskey, D...