Observation of a near-threshold enhancement in th p pbar mass spectrum from radiative J/psi-->gamma p pbar decays

BES Collaboration; Bai, J. Z.; Ban, Y.; Bian, J. G.

Observation of a near-threshold enhancement in th p pbar mass spectrum from radiative J/psi-->gamma p pbar decays

Authors

Description

We observe a narrow enhancement near 2mp in the invariant mass spectrum of ppbar pairs from radiative J/psi-->gamma ppbar decays. The enhancement can be fit with either an S- or P-wave Breit Wigner fuction. In the case of the S-wave fit, the peak mass is below the 2mp threshold and the full width is less than 30 MeV. These mass and width values are not consistent with the properties of any known meson resonance.
5 pages, 4 figures, submitted to Phys. Rev. Lett