Observation of a fine structure in e+e- → hadronsproduction at the nucleon-antinucleon threshold

A study of hadron production at the nucleon-antinucleon threshold has been performed with the CMD-3 detector at the VEPP-2000 e(+)e(-) collider. The very fast rise with about 1 MeV width has been observed in the e(+)e(-) -> p (p) over bar cross section. A sharp drop in the e(+)e(-) -> 3(pi(+)pi(-)) cross section has been confirmed and found to have a less than 2 MeV width, in agreement with the observed fast rise of the e(+)e(-) -> p (p) over bar cross section. For the first time a similar sharp drop is demonstrated in the e(+)e(-) -> K+K-pi(+)pi(-) cross section. The behavior of the e(+)e(-) -> 3(pi(+)pi(-)), K+K-pi(+)pi(-) 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 e(+)e(-) -> 2(pi(+)pi(-)) cross section. (C) 2019 The Author(s). Published by Elsevier B.V.