A significant isospin~l enhancement in the cross sections f'or pp (pn) -* K* (890) Kin: (K*KTnr) is observed at a mass of 2360 ±25 MeV with a width T < 60 MeV. This mass and width are consistent with the U meson and an enhancement reported in a recent Brookhaven National Laboratory backward n~p missing-mass experiment. Whereas we agree with the Brookhaven National Laboratory NN total cross section measurements on the ITI*(2350) position, our width is clearly inconsistent with their value of 140 MeV.With the report of structure in the total cross sections for pp and pd interactions by Abrams et al., 1 we began a study of pp and pn partial cross sections in a bubble chamber experiment. The experiment consisted of an exposure of the Brookhaven National Laboratory 31-in. hydrogen chamber to antiprotons at 1.51, 1.65, 1.80, and 1.95 GeV/c, and the Argonne National Laboratory 30-in. deuterium chamber at 1.60, 1.75, 1.85, and 2.00 GeV/c. The sensitivities at each hydrogen and deuterium momentum correspond to -0.6 and 0.3 event//zb, respectively* These momenta were chosen to include the 71^ (2350) and 7r 0 *(2375) structure of Ref" 1, spaced at approximately 25-MeV intervals. In addition to this structure, other reported boson resonances in this high-mass region are the U meson (M = 2382 ± 24, T<30 MeV, I> 1) observed in the CERN missing-mass experiment of Focacci et al., 2 and an enhancement observed by Anderson et al. 3 in their missing-mass studies of backward inelastic ir~p scattering (M = 2370±17, T = 57 MeV, 7^1).The reactions of particular interest in this study areand pd -^1°(K"> + 7T ""77 ~p s (111 events),-~K + K~77 + 7r~TO s (177 events).The film was scanned for all events with at least one vee. Second scanning was done on 28 % of the hydrogen film and all of the deuterium film. Typical single-scan efficiencies for hydrogen were 90%, and the combined double-scan efficiency for deuterium, where the scanning was somewhat more difficult, was 92 %. After four measurement passes, 90% of all scanned events gave an acceptable kinematic fit for both pp and pn. Kinematic ambiguities, after ionization checks by physicists, were reduced to less than 5%. The 548 events of Reaction (3) were derived from 45 000 four-prong measurements. Since this reaction does not have a vee signature characteristic of neutral-kaon production, extreme care was required in establishing a positive identification from the very large background of pion annihilations. In each case, ionization checks were made by a physicist before the event was accepted., Of the 45 000 measurements, 10 000 gave one-constraint kinematic fits to (3) and 548 survived the ionization cuts. In comparison with Monte Carlo predictions, 4 these methods yielded -80% of the true sample with an effective momentum cutoff of 550 MeV/c (1.8 times minimum ionization) on at least one of the kaon tracks. For cross section purposes, a slowly varying correction, based on the Monte Carlo studies, was applied at each momentum to account for the events where both kaons were too fast t...
