Common explanation of the behavior of some $e^+e^-$ annihilation processes around $\sqrt s$ = 1.9 GeV

Abstract

We show that the behavior of the excitation curves of some $e^+e^-$ annihilation processes close to the nucleon-antinucleon threshold can be explained either by the $\rho(1900)$ resonance itself or by its interference with other resonances. Besides the six-pion annihilation and the $e^+e^- \to K^+K^-\pi^+\pi^-$ and $e^+e^- \to \Phi \pi^0$ processes, we also analyze the final states $\eta \pi^+ \pi^-$, $K^+ K^- \pi^+ \pi^- \pi^0$, and $K^+ K^-\pi^0 \pi^0$, the behavior of which around 1.6 GeV has not yet attracted attention. Analysis of the data on the $e^+e^- \to p \bar p$ and $e^+e^- \to n \bar n$ reactions clearly shows that the $\rho(1900)$ resides above the $n \bar n$ threshold.