# Recent developments in particle yield fluctuation measurements

## TL;DR

This paper reviews recent measurements of particle yield fluctuations in heavy-ion collisions, highlighting how these fluctuations reveal properties of the initial state and phase transitions during medium evolution.

## Contribution

It introduces new observables for forward-backward correlation studies, enhancing the analysis of event-by-event fluctuations in heavy-ion collisions.

## Key findings

- Observation of dynamical fluctuations in particle yields
- Identification of forward-backward correlations
- Proposal of new correlation observables

## Abstract

In relativistic heavy-ion collisions, properties of the initial state and effects arising during evolution of the medium, such as a transition between the hadronic and partonic phases, should reflect themselves in event-by-event fluctuations of the number of produced particles. In this paper, recent measurements of several event-by-event observables, namely, dynamical fluctuations of relative particle yields and forward-backward correlations of different types, are discussed. Also, new observables for forward-backward correlation studies are proposed: correlations between ratios of identified particle yields in two separated acceptance intervals and the correlation between the ratio in one interval and average transverse momentum in another.