Investigating the composition of the K State With K correlations at the LHC

The first measurements of femtoscopic correlations with the particle pair combinations ${\pi }^{±}$K${}_{S}^{0}$ in pp collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K${}_{0}^{⁎}\left(700\right)$ particle that has been considered a tetraquark candidate for over forty years. Source and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction in the ${\pi }^{±}$K${}_{S}^{0}$ system is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, The extracted mass and Breit–Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K${}_{0}^{⁎}\left(700\right)$. The small value and increase of the correlation strength with increasing source size support the hypothesis that the K${}_{0}^{⁎}\left(700\right)$ is a four-quark state, i.e. a tetraquark state of the form $\left({q}_{1},\stackrel{‾}{{q}_{2}},{q}_{3},\stackrel{‾}{{q}_{3}}\right)$ in which ${q}_{1}$, ${q}_{2}$ and ${q}_{3}$ indicate the flavor of the valence quarks of the π and K${}_{S}^{0}$. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K${}_{0}^{⁎}\left(700\right)$ resonance.