Strangeness fluctuations from $K-\pi$ interactions

TL;DR

This study investigates how $K ext{-}\pi$ interactions influence strangeness fluctuations in hot QCD matter, highlighting the importance of accurately modeling broad resonances for thermodynamic predictions.

Contribution

It introduces a method to incorporate empirical $K ext{-}\pi$ phase shifts into thermodynamic calculations, revealing limitations of simplified resonance treatments.

Findings

Simplified models overestimate strangeness fluctuations.

Broad resonances require careful treatment in thermodynamic models.

Empirical phase shifts improve the accuracy of fluctuation predictions.

Abstract

Motivated by recent lattice QCD studies, we explore the effects of interactions on strangeness fluctuations in strongly interacting matter at finite temperature. We focus on S-wave $K\pi$ scattering and discuss the role of the $K_0^*(800)$ and $K^*(1430)$ resonances. The interaction contribution is obtained within the S-matrix formulation of thermodynamics, using the empirical $K\pi$ phase shifts as input. We find that the simplified treatment of the interactions in this channel, employed in the hadron resonance gas approach, leads to an overestimate of the strangeness fluctuations. Thus, our calculation indicates that broad resonances must be treated with caution, when modeling QCD thermodynamics in the hadronic phase.