Understanding the near-threshold structures in $e^{+}{e}^{-}$ annihilation from a unified $N\bar{N}$-interaction perspective

Abstract

Near-threshold structures have been observed in the cross sections for $e^{+}{e}^{-}\to p\bar{p}$, $e^{+}{e}^{-}\to n\bar{n}$ and several non-baryonic final states in the vicinity of the $N\bar{N}$ thresholds. We investigate whether these structures can be understood as manifestations of a common $N\bar{N}$ final-state interaction. The strong $N\bar{N}$ interaction is taken from the chiral EFT description of the coupled ${}^3{S}_1$-${}^3{D}_1$ system constrained by low-energy $N\bar{N}$ scattering data. With this interaction fixed, the $p\bar{p}$ and $n\bar{n}$ cross sections are described by fitting only short-distance electromagnetic production sources, which are assumed to vary slowly over the near-threshold region. The resulting $N\bar{N}$ production amplitudes are then used as input for five inelastic hadronic channels. A simultaneous description of the near-threshold cross sections is obtained, indicating that the observed structures can be consistently interpreted as consequences of the same underlying $N\bar{N}$ dynamics, without introducing separate narrow resonances in individual channels.

Comments: 10 pages, 2 figures and 2 tables