Search for dibaryon resonances of masses between 2.16 and 2.32 GeV/ c2 in the reaction γd → pp π−

Abstract

The reaction γd → pp π − has been studied in order to investigate whether dibaryon resonances contribute to the cross section in the invariant mass region from 2.16 to 2.32 GeV/ c 2. Using a bremsstrahlung photon beam we have determined the invariant mass M ppπ by detecting both outgoing protons in large solid angle TOF spectrometers, thus achieving a statistical accuracy of 1 to 2% per 2.5 MeV/ c 2 bin, a mean invariant mass resolution of 4.4 MeV/ c 2(σ) and a smooth M ppπ acceptance. Despite the resulting high resonance sensitivity no evidence for a dibaryon resonance in the M ppπ distribution was found. Assuming an isotropic phase space decay we estimate the upper limit for the dibaryon resonance cross section to be 1μb for masses around 2.23 GeV/ c 2 and resonance widths between 5 and 40 GeV/ c 2.