Speaker
Description
Long-range multiparticle correlations as observed in the ultrarelativistic collisions of heavy ions at RHIC and the LHC has long been held as a signature of hydrodynamic flow in the novel phase of hot and dense matter known as the quark gluon plasma. However, these correlations, manifesting most simply as an elliptical Fourier coefficient or v$_{2}$, has subsequently been observed not just in collisions of heavy ions, but also in collisions of light ions, in collisions of protons with ions, in high-multiplicitiy proton-proton collisions, in ultra-peripheral heavy ion collisions, and even recently in analysis of archival data of high energy e+e- collisions from the ALEPH detector at LEP. In this talk the state of multiparticle correlation measurements across collision systems will be reviewed, with a particular focus on what we can and cannot conclude regarding the minimal conditions for flow-like signals, given current experimental limitations. Furthermore, the distinction between a flow-like signal and the underlying mechanism being true hydrodynamic flow will be explored, as the minimal conditions for observing each should be considered distinct. Finally, future prospects for measuring flow in small systems will be discussed.
