Speakers
Description
One of the main surprises brought by the heavy ion program at the LHC is the observation of long-range correlations in collisions involving relatively small systems, like proton-proton or proton-lead. Similar phenomena were previously observed in collisions between two heavy nuclei, like Au+Au (at RHIC) and Pb+Pb (at the LHC) and in that context they were associated with collective phenomena, like hydrodynamic flow. Such phenomena look indeed natural for systems which are sufficiently large, long-lived, and which have relatively strong interactions.
Yet, the fact that they are also seen in smaller systems rises interesting questions.
Are these phenomena a signal of genuine collective motion, like flow ?
Or are they related to other sources, like jets or glasma correlations in the initial state?
What are the limits of hydrodynamics, in terms of size and lifetime ?
What is the smallest droplet of liquid that can meaningfully exist ?
Such questions give often the opportunity of intense debates among experts, at various conference and also via dedicated papers.
