On the structure of the X(1835) baryonium

TL;DR

This paper proposes that the X(1835) baryonium structure observed in J/psi decays can be explained by a broad quasi-bound N-Nbar state, with its observed features resulting from interference effects.

Contribution

It introduces a semi-phenomenological potential model that accounts for the X(1835) as a quasi-bound N-Nbar state, explaining experimental observations.

Findings

The X(1835) peak is due to a broad quasi-bound N-Nbar state.

Interference effects shape the observed peak structure.

The model fits all N-Nbar scattering data.

Abstract

The measurement by the BES collaboration of J/psi -> gamma p pbar decays indicates an enhancement at the p-pbar threshold. In another experiment BES finds a peak in the invariant mass of pi-mesons produced in the possibly related decay J/psi -> gamma pi+ pi- eta'. Using a semi-phenomenological potential model which describes all the N-Nbar scattering data, we show that the explanation of both effects may be given by a broad quasi-bound state in the spin and isospin singlet S wave. The structure of the observed peak is due to an interference of this quasi-bound state with a background amplitude and depends on the annihilation mechanism.