Initial State Summary of Hard Probes 2020

TL;DR

This paper reviews recent developments in understanding the initial state of heavy ion collisions, focusing on nuclear descriptions, interactions, geometry, and hydrodynamic modeling, with implications for probing the produced matter.

Contribution

It summarizes new insights from Hard Probes 2020 on the initial conditions and modeling approaches in heavy ion collision studies.

Findings

Advances in describing the initial nuclear state.

Improved understanding of collision geometry.

Impacts on interpreting hard and electromagnetic probes.

Abstract

The description of the initial state of heavy ion collisions, which covers the description of the incoming nuclei, the initial hard and soft interactions, the resulting spatial geometry of the produced matter, as well as the dynamic approach to a medium well described by hydrodynamics, has important consequences for the study of hard and electromagnetic probes. I will review new developments presented at Hard Probes 2020 that have an impact on these aspects of our understanding of the initial state of heavy ion and smaller system collisions.