Abstract
We present the first ever measurements of femtoscopic correlations between the KS0 and K± particles. The analysis was performed on the data from Pb–Pb collisions at sNN=2.76 TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding via the a0(980) resonance. The extracted kaon source radius and correlation strength parameters for KS0K− are found to be equal within the experimental uncertainties to those for KS0K+. Comparing the results of the present study with those from published identical-kaon femtoscopic studies by ALICE, mass and coupling parameters for the a0 resonance are tested. Our results are also compatible with the interpretation of the a0 having a tetraquark structure instead of that of a diquark.
Highlights
Identical boson femtoscopy, especially of identical charged pions, has been used extensively over the years to study experimentally the space–time geometry of the collision region in highenergy particle and heavy-ion collisions [1]
The fitting uncertainties are taken to be the extreme values of the 1σ fit contours in R vs. λ
The results for the R and λ parameters extracted in the present analysis from K0S K± femtoscopy, averaged over the two baseline fit methods and averaged over K0S K+ and K0S K−, are presented in Table 2 and in Figs. 4 and 5
Summary
Especially of identical charged pions, has been used extensively over the years to study experimentally the space–time geometry of the collision region in highenergy particle and heavy-ion collisions [1]. The pair-wise interactions between the identical kaons that form the basis for femtoscopy are for K±K± quantum statistics and the Coulomb interaction, and for K0S K0S quantum statistics and the final-state interaction through the f0(980)/a0(980) threshold resonances. One can consider the case of non-identical kaon pairs, e.g. K0S K± pairs. Besides the non-resonant channels which may be present, e.g. non-resonant elastic scattering or free-streaming of the kaons from their freeze-out positions to the detector, the other only pair-wise interaction allowed for a K0S K± pair at freeze out from the collision system is a final-state interaction (FSI) through the a0(980) resonance. The other pair-wise interactions present for identical-kaon pairs are not present for K0S K± pairs because: a) there is no quantum statistics enhancement since the kaons are not identical, b) there is no Coulomb effect since one of the kaons is uncharged, and c) there is no strong FSI through the f0 reso-
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