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Zusammenfassung: <jats:p>A study of hadron production at the nucleon-antinucleon threshold has been performed with the CMD-3 detector at the VEPP-2000 <jats:italic>e</jats:italic><jats:sup>+</jats:sup><jats:italic>e</jats:italic><jats:sup>−</jats:sup> collider. A very fast rise with an about 1 MeV width has been observed in the <jats:italic>e</jats:italic><jats:sup>+</jats:sup><jats:italic>e</jats:italic><jats:sup>−</jats:sup>→ <jats:italic>pp</jats:italic>̅ cross section. A sharp drop in the <jats:italic>e</jats:italic><jats:sup>+</jats:sup> <jats:italic>e</jats:italic><jats:sup>−</jats:sup>→ 3(π<jats:sup>+</jats:sup>π<jats:sup>−</jats:sup>) cross section has been con?rmed and found to have a width of less than 2 MeV, in agreement with the observed fast rise of the <jats:italic>e</jats:italic><jats:sup>+</jats:sup><jats:italic>e</jats:italic><jats:sup>−</jats:sup>→ <jats:italic>pp</jats:italic>̅ cross section. For the ?rst time a similar sharp drop is demonstrated in the <jats:italic>e</jats:italic><jats:sup>+</jats:sup><jats:italic>e</jats:italic><jats:sup>−</jats:sup>→ <jats:italic>K</jats:italic><jats:sup>+</jats:sup> <jats:italic>K</jats:italic><jats:sup>−</jats:sup>π<jats:sup>+</jats:sup>π<jats:sup>−</jats:sup> cross section. The behavior of the <jats:italic>e</jats:italic><jats:sup>+</jats:sup><jats:italic>e</jats:italic><jats:sup>−</jats:sup>→ 3(π<jats:sup>+</jats:sup> π<jats:sup>−</jats:sup>), <jats:italic>K</jats:italic><jats:sup>+</jats:sup> <jats:italic>K</jats:italic><jats:sup>−</jats:sup>π<jats:sup>+</jats:sup>π<jats:sup>−</jats:sup> cross sections cannot be explained by an interference of any resonance amplitude with continuum, therefore this phenomenon cannot be due to a narrow near-threshold resonance. No such structure has been observed in the <jats:italic>e</jats:italic><jats:sup>+</jats:sup><jats:italic>e</jats:italic><jats:sup>−</jats:sup>→ 2(π<jats:sup>+</jats:sup>π<jats:sup>−</jats:sup>) cross section.</jats:p>
Umfang: 07002
ISSN: 2100-014X
DOI: 10.1051/epjconf/201921207002