Investigating the composition of the K${}_0^{\ast }(700)$ state with ${\pi }^{\pm }$K${}_{\mathrm{S}}^0$ correlations at the LHC

Abstract

The first measurements of femtoscopic correlations with the particle pair combinations ${\pi }^{\pm }$K${}_{\mathrm{S}}^0$ 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${}_0^{\ast }(700)$ 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 ${\pi }^{\pm }$K${}_{\mathrm{S}}^0$ 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${}_0^{\ast }(700)$. The small value and increase of the correlation strength with increasing source size support the hypothesis that the K${}_0^{\ast }(700)$ is a four-quark state, i.e. a tetraquark state of the form $({\mathrm{q}}_1,\overline{{\mathrm{q}}_2},{\mathrm{q}}_3,\overline{{\mathrm{q}}_3})$ in which ${\mathrm{q}}_1$, ${\mathrm{q}}_2$, and ${\mathrm{q}}_3$ indicate the flavor of the valence quarks of the $\pi$ and K${}_{\mathrm{S}}^0$. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K${}_0^{\ast }(700)$ resonance.

arXiv comment24 pages, 4 captioned figures, 4 tables, authors from page 18, published version, figures at http://alice-publications.web.cern.ch/node/10644

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