Deuteron breakup by 1.15 GeV protons and excitation of the Δ isobar

The pd→npp reaction has been measured using circulating 1.15 GeV protons, a gas jet target and scintillation detectors selecting scattered protons with energy above 30 MeV. The distribution of the two-proton invariant mass has a maximum at 2.13±0.01 GeV/c2 and a width of 130±10 MeV/c2 (FWHM). We see no evidence of narrow (gG < 30 MeV/c2) peaks in the phase-space region selected. The mass of X, excited in the pN→nX elementary process, is 40 MeV/c2 smaller than the mass of a real Δ isobar.