# Measuring K$^0_{\rm S}$K$^{\rm \pm}$ interactions using Pb-Pb collisions at ${\sqrt{s_{\rm NN}}=2.76}$ TeV

## TL;DR

This paper reports the first femtoscopic measurements of K0sK± interactions in Pb-Pb collisions at 2.76 TeV, providing insights into the $a_0(980)$ resonance and its possible tetraquark structure.

## Contribution

It introduces the first measurement of femtoscopic correlations between K0s and K± particles in heavy-ion collisions, constraining the properties of the $a_0(980)$ resonance.

## Key findings

- Correlation parameters for K0sK− and K0sK+ are consistent within uncertainties.
- Results support the $a_0(980)$ resonance being a tetraquark rather than a diquark.
- Mass and coupling parameters of the $a_0$ are constrained by the data.

## Abstract

We present the first ever measurements of femtoscopic correlations between the K$^0_{\rm S}$ and K$^{\rm \pm}$ particles. The analysis was performed on the data from Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding via the $a_0(980)$ resonance. The extracted kaon source radius and correlation strength parameters for K$^0_{\rm S}$K$^{\rm -}$ are found to be equal within the experimental uncertainties to those for K$^0_{\rm S}$K$^{\rm +}$. Comparing the results of the present study with those from published identical-kaon femtoscopic studies by ALICE, mass and coupling parameters for the $a_0$ resonance are constrained. Our results are also compatible with the interpretation of the $a_0$ having a tetraquark structure over that of a diquark.