Pion interferometry (HBT') measurements relative to the reaction plane provide an estimate of the transverse source anisotropy at freeze-out, which probes the system dynamics and evolution duration. Measurements by the STAR Collaboration indicate that the source is extended increasingly out-of-plane with increasing impact parameter, suggesting a short evolution duration, roughly consistent with estimates based on azimuthally-integrated HBT measurements.

PACS numbers: 25.75.Gz, 25.75.Ld