Observation of a Fine Structure in $e^+e^- \to$ hadrons Production at the Nucleon-antinucleon Threshold

Understand

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.

• A very fast rise with about 1 MeV width has been observed in the $e^+e^- \to p\bar p$ cross section.
• A sharp drop in the $e^+e^- \to 3(\pi^+\pi^-)$ cross section has been confirmed and found to have a less than 2 MeV width, in agreement with the observed fast rise of the $e^+e^- \to p\bar p$ cross section.
• For the first time a similar sharp drop is demonstrated in the $e^+e^- \to K^+K^-\pi^+\pi^-$ cross section.