Collectivity and “Quark-Gluon Plasma” in small collision systems

by Dr Zhenyu Chen (Stony Brook)

Tuesday 11 Sep 2018, 10:30 → 11:30 Asia/Shanghai

B105 (CHEP)

In ultra-relativistic collisions of large, heavy nuclei (e.g. Au or Pb), a new state of nuclear matter consisting of liberated quarks and gluons is formed at a temperature of trillion Kelvins, commonly referred to as Quark Gluon Plasma (QGP). The QGP was found to exhibit collective behavior and flow as a nearly “perfect” fluid. The elementary collision systems such as proton-proton (pp) or proton-nucleus (pA), which were thought to be too small and dilute to form a QGP, were treated as references in understanding the perfect fluidity in large heavy ion systems. Surprisingly, Recent years, evidence for collective effects has been revealed in pp and pPb collisions when looking at events releasing large number of particles. The experimental observations lead to a debate of the formation of QGP in those small collision systems. In this talk, I will go over key findings related to the possible QGP formation in pp and pA systems. Their implications to the paradigm of heavy ion physics, as well as future opportunities, will also be discussed.