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An amplitude analysis for the reaction π+ p → π+π−π0 Δ++ at 7 GeV/c has been performed using the isobar model for the 3π system. The 3π-mass covers the range from 0.82 to 1.90 GeV. We observe strong A2 production. The spin parity of the ω ∗ (1700) is determined to be 3−. No significant A1 production can be seen.

In a 48 000-picture exposure of the Fermilab 30-inch hydrogen bubble chamber to a 205 GeV/ c π − beam, we have measured 169 events of the reaction, π − p → π − π + π − p, with a cross section of 635 ± 61 μ b. This reaction proceeds almost entirely via low mass π − → 3 π and p → p ππ dissociation. Factorization is satisfied for p → pππ dissociation in πp and pp interactions.

A study of elastic scattering, one-pion production and annihilation reactions in pp interactions at 5.7 GeV/c was carried out, from the two-prong events, obtained in the hydrogen bubble chamber exposed at CERN. Single particle distributions for the reactions pp → ppπ0, pp → pnπ+ and pp → pnπ− are presented. The study of the squared momentum transfer distributions with and without charge exchange in the cross channel shows different behavior of the slope parameters versus the mass of the produced (Nπ) system. The cross sections for isobar production and for diffractive dissociation in the one-pion production reactions are obtained from a detailed Dalitz plot analysis. The results of the analysis of the decay angular distributions for the N(1510) and for the N(1680) produced in these reactions are in agreement with J = 32 and J = 52 assignment, respectively. The cross sections of the annihilation reactions pp → π+π− and pp → π+π−π0 are determined. Finally, we give some as aspects of the mass distributions for the last reaction.

The inclusive ϱ ° production cross section has been measured in the reaction π − p → π + π − X at 205 GeV/ c . We find σ ( ϱ ° ) = 13.5 ± 3.4 mb, with most of the production occuring in the central region. Assuming σ ( ϱ + ) ≈ σ ( ϱ − ) ≈ σ ( ϱ ° ), it is concluded that approximately one-third of the pions at this energy come from ϱ -decay.

A new method of obtaining an experimental lower bound on the r.m.s. impact parameter of an exclusive process is applied to data on pp → ppπ+π− at 7–25 and 205 GeV/c and on π−p → π−pπ+π− at 16 and 205 GeV/c. The overall lower bounds are compared with geometrical and multiperipheral model predictions, and are shown to rule out the version of the geometrical model in which these processes become central at high energies. Our results for diffractive regions of longitudinal phase space favour a peripheral impact parameter profile for inelastic diffraction. In a related study of transverse momentum correlations in these processes, we find a predominance of “nearest-neighbour” correlations between transverse momentum transfers.

In 205 GeV / c π − p inelastic interactions, negative particles with transverse momentum greater than 1.0 GeV / c moving forward in the center of mass outnumber similar positive particles by a factor of 3.7 to 1, greatly in excess of the corresponding ratio for small transverse momentum. The asymmetry is reversed in the backward direction. The forward asymmetry is most prominent in 2-, 4-, and 6-prong interactions, but both forward and backward asymmetries are also substantial for higher multiplicity interactions.

The continuum ambiguity is defined as a phase factor not determined by those amplitude zeros near the physical region that can be directly deduced from the data; such a factor may be approximated by a polynomial whose zeros are far from the physical region. A study of recent TIN partial wave analysis (CUTKOSKY76 and HOHLER78) reveals that such a phase is either null or negligeable; CUTKOSKY76' s amplitude is found similar to that of a partial wave analysis based on Barrelet zeros. We give general arguments based on the notion of "peripheral resonances" to explain this situation. Our arguments imply that Atkinson"s {pi}{sup +}p "continuous ambiguity" is not relevant to the reliability of Barrelet-zero amplitude analysis.

A particular case of a Mueller formula describing the absence of long-range two-particle correlations is used to predict double-pomeron cross sections from available data on single-diffraction dissociation. Although success of the formula in this application would immediately verify the double-pomeron hypothesis, the converse is not true because the formula may be invalidated by prominent low-energy resonances (such as the f 0 ) in the pomeron-pomeron total cross section. Low-statistics experiments at s = 200 and 400 GeV 2 are in order of magnitude agreement with the formula.