Results are presented from a search for the production of narrow p¯p states in antiproton interactions at 8.3 and 13.0 GeV/c. Cross-section upper limits have been established for four candidate baryonium states. The upper limits (95% probability level) range from 0.21 to 1.29 μb for inclusive forward production, and from 0.11 to 0.89 μb for backward production in the final state ωf0(p¯p).
CROSS SECTIONS ARE UPPER LIMITS OF 95 PCT CL.
CROSS SECTIONS ARE UPPER LIMITS OF 95 PCT CL.
In a single-arm spectrometer experiment, high-precision measurements of dσdt for π−p, K−p, and p¯p elastic scattering have been made at 8 and 16 GeV/c. The π−p data show rich structure at 8 GeV/c, indicative of strong non-Pomeron contributions, while the 16-GeV/c data are much smoother. For −t≳1 (GeV/c)2 there is a strong s dependence while there is very little for −t<1 (GeV/c)2. For p¯p scattering the forward region is smoothly diffractive for −t<0.4 (GeV/c)2 and shows antishrinkage. The exponential slope parameter b is measured to be 12.36 ± 0.04 (GeV/c)−2 at 8 GeV/c and 11.40 ± 0.04 (GeV/c)−2 at 16 GeV/c. The structure near −t=0.6 (GeV/c)2 seen at lower energies is still obvious at 16 GeV/c. The K−p data show some structure at 8 GeV/c, but can be represented adequately by a quadratic exponential form. At 16 GeV/c the K−p angular distribution shows antishrinkage and lies above the 8-GeV/c cross section for 0.11<−t<0.8 (GeV/c)2.
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We have measured the mean charged multiplicity n¯CH as a function of transverse momentum p⊥ of the forward proton in the reaction p+p→p+MM for five intervals of missing mass (MM) using our Multiparticle Argo Spectrometer System. We observe an increase of n¯CH for p⊥>1 GeV/c.
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Differential cross sections have been measured for nucleon-isobar production and elastic scattering in p−p interactions from 6.2 to 29.7 GeVc in the laboratory angle range 8<θsc<265 mrad. N*' s at 1236, 1410, 1500, 1690, and 2190 MeV were observed. Computer fits to the mass spectra under varying assumptions of resonance and background shapes show that conclusions on t and s dependence are only slightly affected despite typical variations in absolute normalization of ± 35%. Logarithmic t slopes in the small- |t| range are ∼15 (GeVc)−2 for the N*(1410), ∼5 (GeVc)−2 for the N*'s at 1500, 1690, and 2190 MeV, and ∼9 (GeVc)−2 for elastic scattering. Also for the small- |t| data, cross sections for N*'s at 1410, 1500, 1690, and 2190 MeV and for elastic scattering vary only slightly with Pinc consistent with the dominance of Pomeranchuk exchange and with diffraction dissociation. A fit of N*(1690) total cross sections to the form σ∝P−n gives n=0.34±0.06, while for elastic scattering n=0.20±0.05. For the N*(1690) the effective Regge trajectory has the slope αeff′(0)=0.38±0.17. When compared with N* production in π−, K−, and p¯ beams these data also agree with approximate factorization of the Pomeranchuk trajectory. N*(1236) cross sections are consistent with other measurements at similar momenta. For −t>1 (GeVc)−2, elastic scattering cross sections decrease approximately as Pinc−2, and they and N*(1500)− and N*(1690)− production cross sections have t slopes consistent with 1.6 (GeVc)−2.
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A missing mass spectrometer search was made for several two-body, double charge exchange reactions, including backward K −p and p̄p elastic scattering at 8 and 16 GeV/ c and small momentum transfer. No examples of any of these processes were observed.
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Angular distributions are presented for p¯−p elastic scattering at 8 and 16 GeV/c for |t|<1.3 (GeV/c)2. At both energies there is structure in the differential cross sections in the region 0.5<~|t|<~1.0 (GeV/c)2, similar to that observed at lower energies. The diffraction peak continues to expand with increasing incident momentum.
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