Simplifying Strangeness Fluctuations through Balance Functions in Proton-Proton Collisions

TL;DR

This paper links fluctuation observables in proton-proton collisions to balance functions, showing they mainly reflect strangeness conservation effects, and compares model predictions with experimental data.

Contribution

It demonstrates that key fluctuation measures can be expressed through balance functions, providing a new microscopic interpretation and a baseline for testing hadronization models.

Findings

Balance functions relate to fluctuation observables and strangeness conservation.

Thermal-FIST reproduces fluctuation magnitudes but not the shape of balance functions.

Models need to accurately describe balance functions to match experimental data.

Abstract

Recent measurements of event-by-event fluctuations of multistrange baryons and kaons in proton-proton collisions by ALICE have been proposed as sensitive probes to distinguish between thermal and string-based hadronization mechanisms. We demonstrate that two key observables -- the normalized net-$\Xi$ second-order cumulant and the net-$K$--net-$\Xi$ Pearson correlation coefficient -- can be re-expressed in terms of balance function integrals, thereby revealing their underlying microscopic content, and relating them to balance functions previously measured by ALICE. This allows us to show that both observables probe the same physics and primarily measure the impact of strangeness conservation on hadronization. We compare both sets of ALICE data with two contrasting models, PYTHIA and Thermal-FIST. Importantly, while Thermal-FIST can reproduce the magnitude of fluctuation observables, it fails to describe the shape of the measured balance functions. Our findings highlight the importance of balance functions as precision tools for testing hadronization models in small collision systems and propose a robust baseline for future studies exploring hadronization dynamics in QCD matter.