Abstract
The first measurements of the scattering parameters of ΛK pairs in all three charge combinations (ΛK+, ΛK−, and ΛKS0) are presented. The results are achieved through a femtoscopic analysis of ΛK correlations in Pb-Pb collisions at sNN=2.76 TeV recorded by ALICE at the Large Hadron Collider. The femtoscopic correlations result from strong final-state interactions and are fit with a parametrization allowing for both the characterization of the pair emission source and the measurement of the scattering parameters for the particle pairs. Extensive studies with the THERMINATOR 2 event generator provide a good description of the nonfemtoscopic background, which results mainly from collective effects, with unprecedented precision. Furthermore, together with HIJING simulations, this model is used to account for contributions from residual correlations induced by feed-down from particle decays. The extracted scattering parameters indicate that the strong force is repulsive in the ΛK+ interaction and attractive in the ΛK− interaction. The data hint that the ΛKS0 interaction is attractive; however, the uncertainty of the result does not permit such a decisive conclusion. The results suggest an effect arising either from different quark-antiquark interactions between the pairs (ss¯ in ΛK+ and uu¯ in ΛK−) or from different net strangeness for each system (S=0 for ΛK+, and S=−2 for ΛK−). Finally, the ΛK systems exhibit source radii larger than expected from extrapolation from identical particle femtoscopic studies. This effect is interpreted as resulting from the separation in space-time of the single-particle Λ and K source distributions.3 MoreReceived 5 June 2020Accepted 30 March 2021DOI:https://doi.org/10.1103/PhysRevC.103.055201Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.©2021 CERN, for the ALICE CollaborationPhysics Subject Headings (PhySH)Research AreasParticle & resonance productionParticle correlations & fluctuationsParticle interactionsRelativistic heavy-ion collisionsNuclear Physics
Highlights
Femtoscopy is an experimental method used to study the space-time characteristics of the particle emitting sources in relativistic particle collisions [1,2]
In order to reduce the contamination to the two-particle correlations due to pairs sharing daughters, track splitting, and track merging, two main pair rejection procedures are applied: a shared daughter restriction, and an average separation constraint
These contribute to the observed correlation function, and obscure its relation to the primary K system
Summary
Femtoscopy is an experimental method used to study the space-time characteristics of the particle emitting sources in relativistic particle collisions [1,2]. Which are difficult or impossible to measure otherwise The subjects of this analysis, K pairs, interact only strongly; the studied femtoscopic signals are free from quantum statistical and Coulomb interaction effects. This paper presents the first measurements of the scattering parameters of K pairs in all three charge combinations ( K+, K−, and KS0). The scattering parameters, along with pair emission source sizes, are extracted with a femt√osscNoNpi=c analysis of K correlations in Pb-Pb collisions at 2.76 TeV measured by the ALICE experiment at the. These correlations result from strong final-state interactions, and are fit with a parametrization by Lednický and Lyuboshitz [16]. In Appendix C, the THERMINATOR 2 event generator is used to demonstrate the effect on a one-dimensional femtoscopic fit of a nonzero space-time separation between the single particle sources. K+⊕ K−, K− for K−⊕ K+, and KS0 for KS0⊕ KS0), and K is used to describe all K combinations
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