<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>N</mml:mi><mml:mover accent="true"><mml:mrow><mml:mi>N</mml:mi></mml:mrow><mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> production in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> annihilation near the threshold revisited
A. I. Milstein, S. G. Salnikov
Abstract
Production of $p\overline{p}$ and $n\overline{n}$ pairs in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation near the threshold of the process is discussed with account for the new experimental data that appeared recently. Since a significant part of these new data was obtained at energies noticeably exceeding the threshold, we also take into account the form factor describing the amplitude of $N\overline{N}$ pair production at small distances. The effective optical potential, which describes a sharp dependence of the $N\overline{N}$ production cross sections near the threshold, consists of the central potential for $S$ and $D$ waves and the tensor potential. These potentials differ for states with isospin $I=0$ and $I=1$ of the $N\overline{N}$ pair. The optical potential describes well $N\overline{N}$ scattering phases, the cross sections of $p\overline{p}$ and $n\overline{n}$ production in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation near the threshold, and the electromagnetic form factors ${G}_{E}$ and ${G}_{M}$ for protons and neutrons, as well as the cross sections of the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}6\ensuremath{\pi}$ and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$.