Event geometrical anisotropy and fluctuation viewed by HBT interferometry

Abstract

Azimuthal angle dependence of the pion source radii was measured applying the event shape selection at the PHENIX experiment. The measured final source eccentricity is found to be enhanced when selecting events with higher magnitude of the second-order flow vector, as well as the elliptic flow coefficient $v_{2}$. The spatial twist of the particle-emitting source was also explored using a transport model. Results indicate a possible twisted source in the final state due to the initial longitudinal fluctuations.