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A study of 205-GeV/c ${\ensuremath{\pi}}^{\ensuremath{-}}p$ interactions has been made with a 48 800-picture exposure in the bare Fermilab 30-inch hydrogen bubble chamber. The average number of charged particles produced per inelastic interaction is 7.99\ifmmode\pm\else\textpm\fi{}0.06. The elastic cross section is 3.18\ifmmode\pm\else\textpm\fi{}0.13 mb and the total cross section is 24.19\ifmmode\pm\else\textpm\fi{}0.44 mb. The inclusive cross sections for neutral-particle production are: $\ensuremath{\sigma}(\ensuremath{\gamma})=171.3\ifmmode\pm\else\textpm\fi{}15.3$ mb, $\ensuremath{\sigma}({K}_{S}^{0})=3.64\ifmmode\pm\else\textpm\fi{}0.61$ mb ($xl0.3$), $\ensuremath{\sigma}(\ensuremath{\Lambda})=1.71\ifmmode\pm\else\textpm\fi{}0.34$ mb ($xl0.3$), and $\ensuremath{\sigma}(\overline{\ensuremath{\Lambda}})=0.59\ifmmode\pm\else\textpm\fi{}0.23$ mb ($xl0.1$). The average number of ${\ensuremath{\pi}}^{0}'\mathrm{s}$ produced per inelastic collision is consistent with a linear rise with the number of charged particles, and about equal to the number of produced ${\ensuremath{\pi}}^{\ensuremath{-}}$ or ${\ensuremath{\pi}}^{+}$. The average number of ${K}^{0}'\mathrm{s}$, $\ensuremath{\Lambda}'\mathrm{s}$, and $\overline{\ensuremath{\Lambda}}'\mathrm{s}$ is consistent with very little dependence on the number of charged particles. General characteristics of neutral-particle production are presented and compared with other experiments. For each topology the produced neutral energy is $\ensuremath{\sim}\frac{1}{3}$ of the incident energy.

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.

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.

Inelastic channels in ..pi../sup -/p interactions at 205 GeV/c are studied as a function of charged-particle multiplicity n/sub ch/. Experimental tests are made which are sensitive to the charge-dependent behavior of the particles, particularly at high and low rapidities. A set of new variables useful for the study of these processes is introduced. Effects which may be attributed to leading particles or leading jets are present to some extent for all n/sub ch/. Among the results presented, it is shown that at this energy there is no ''central region'' which is completely free of effects which are correlated with the charges of the incident particles. Qualitative interpretation of the results in terms of cluster-model ideas is presented; a specific simple model is calculated and compared with the data.

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.

Coherent production of K π, K 2π and K 3π final states from A ∼ 20 nuclei by K− beams of 5.5, 10.0 and 12.7 GeV is analyzed. Final states with ⩽ 2πO are included. Coherent K π production occurs (although forbidden via 0+ exchange) and is dominated by the K ∗ (890). The shape of the t distribution, the alignment of the produced meson and the ratio of the cross section on nuclei to that on hydrogen are consistent with optical model predictions assuming that K ∗ (890) are produced on single nucleons by exchange of isoscalar trajectories of natural parity (JP = 1−, 2+, etc.) and that the K ∗ (890) absorption in nuclear matter equals that of the K−. Coherent K ππ production (allowed via 0+, 1−, 2+, etc. exchange) is dominated by the Q phenomenon. A Dalitz plot and angular correlation analysis yields values for K ϱ/ K ∗ π fractions, and shows that J P = 1 + S-wave K ∗ π dominates the coherently produced Q. The helicity of the Q is found to be compatible with 0. The Q− -nucleaon total cross section is estimated to be 0.98−0.37+024 times the K − -nucleon total cross section from a comparison of the coherent Q-production cross section with corresponding hydrogen cross sections at 10 and 12.7 GeV. We observe coherent production of K ω. The ration K ω/ K ππ coherently produced in the Q mass region is (4 ± 1)%. Coherent production of K − π + π − and K O π + π − π O is observed in the L region. Coherent production is not observed in the K4π channels.

Partial cross-sections are presented for ρ0, f0 and ω0 production by 15 and 16 GeV/c π− in the incoherent reactions π−A → π+π−A’ and π−A → π+π−π0A’ on nuclei of C2F5Cl in a HLBC. Using these results and a nuclear-interaction model, the production cross-sections of these resonances in the corresponding reactions on protons,i.e. π−p → ρ0n, π−p → f0n and π−p → ω0n, are calculated as a function of the absorption cross-section of the produced resonance in nuclear matter. Difficulties in separating those reactions from other sources of ρ0, etc., in nuclear reactions are discussed.

Author(s): Winkelmann, F.C.; Abrams, G.S.; Bingham, H.H.; Chew, D.M.; Daugeras, B.Y.; Fretter, W.B.; Friedberg, C.E.; Goldhaber, G.; Graves, W.R.; Johnson, A.D.; Kadyk, J.A.; Stutte, L.; Trilling, G.H.; Yost, G.P.; Bogert, D.; Hanft, R.; Huson, F.R.; Ljung, D.; Pascaud, C.; Pruss, S.; Smart, W.M.