Event-by-Event Fluctuations

TL;DR

This review discusses how fluctuations in heavy ion collisions can signal phase transitions, exploring their theoretical basis, experimental data, and differences between small and large systems.

Contribution

It systematically examines the principles and practices of fluctuations in heavy ion collisions, highlighting their role as signals of phase transitions and comparing theory with experimental data.

Findings

Fluctuations serve as potential signals of phase transitions.

Correlation functions are related to measurable fluctuations.

Differences exist between fluctuations in small and large systems.

Abstract

In this review, we systematically examine the principles and the practices of fluctuations such as the momentum and the charge fluctuations as applied to the heavy ion collisions. Main emphases are: (i) Fluctuations as signals of phase transition (ii) Relationship between correlation functions and fluctuations (iii) Qualitative difference between fluctuations in small systems and large systems. Whenever available, theoretical results are compared with data from RHIC and SPS.