Are the collective phenomena a universal feature of the hadronic matter created in p–p, p–A and A–A colliding systems?

Abstract

Collective phenomena in ion–ion collisions are well-known, but the research in small systems, like proton–proton and proton-lead, is starting both from the experimental and theoretical side. In this paper, we present a short review of the most important observables related to flow, as well as phenomenological results to explain the Relativistic Heavy Ion Collider and Large Hadron Collider results. Different variables and their relations to collectivity in small systems are discussed.