Speaker
Description
The primary goal of the ultra-relativistic heavy-ion collision program at the Large Hadron Collider (LHC) is to study the properties of the Quark-Gluon Plasma (QGP), a novel state of strongly interacting matter which exists in the early universe. Anisotropic flow, which quantifies the anisotropy of the momentum distribution of final state particles, is sensitive to the fluctuating initial conditions and the transport properties of the created QGP. The successful description of the measured anisotropic flow coefficients by hydrodynamic calculations suggests that the created medium behaves like a nearly perfect fluid. However, the observation of collective flow phenomena in high energy proton-lead and proton-proton collision triggers intense discussions. Whether the smallest droplet of QGP has been produced in these collisions or other physics mechanisms will be attributed to this phenomenon, is under debate.
In this talk, I will present the latest developments of flow studies at the LHC, including both recent theoretical model calculations and experimental measurements in proton-lead collisions at $\sqrt{s_{_{\rm NN}}} =$ 5.02 TeV and proton-proton collisions at $\sqrt{s} =$ 13 TeV. I will especially highlight the current challenge of the hydrodynamic description on multi-particle cumulants measurements, and try to answer whether we have the evidence of the creation of a small droplet of QGP in these small collision systems.
