A. Zieminski

ϱ0 and f production in π+p interactions

Abstract Inclusive ϱ 0 and f(1270) production are analysed in π + p collisions at 8, 16 and 23 GeV/ c . The ϱ 0 cross section increases with energy such that the ϱ 0 /π − ratio remains constant. Emphasis is laid on cross sections as a function of the transverse momentum and of the Feynman x variable. The ϱ 0 s can be attributed to two sources: some ϱ 0 s are centrally produced, but there is a pronounced forward peak. The distribution of leptons coming from ϱ 0 decay is discussed.

Production of ρ0 and f in π−p interactions at 16 GeV/c and separation into fragmentation and central components

The production of ρ0(770) and f(1270) is studied in π−p interactions at 16 GeV/c. By comparison with inclusive K∗0 production in the reaction K−p → K∗0 + anything, and with inclusive ρ0 production in the reaction pp → ρ0 + anything, it is found that the data can be interpreted in terms of two production processes: the central production of resonances and the fragmentation of the beam particle. For the π−p reaction, the inclusive ρ0 beam fragmentation cross section is 3.1 ± 0.3 mb while that for central production is 1.6 ± 0.5 mb. The ρ0 central production cross section is consistent with increasing with energy as ln s behaviour. The ratio of ρ0 to π− inclusive cross sections (excluding the leading π−) is ∼0.2, independent of energy. The ρ0 to π− ratio increases as a function of pT to a constant value of ∼12 above 1 GeV/c. The ρ (charged and neutral) and f decays account for (25 ± 4)% and (1.4 ± 0.3)%, respectively, of all pions produced.

Study of π−π− scattering in π−n interactions at high energies

Abstract We have measured the inclusive cross section for the reaction π − n→pX −− at 21, 205 and 360 GeV/ c in the kinematic region | t np | c ) 2 . The differential cross sections can be described qualitatively by the reggeized one-pion-exchange amplitude at all momenta studied; however, there is evidence for the contribution of other amplitudes. The extracted π − π − total cross section for 4⪅ s ππ ⪅340 GeV 2 is of the order of 10–12 mb. The average number of charged particles and dispersion of the charged particle multiplicity distributions for various s ππ intervals are compatible with results observed in hadron-proton interactions.

Multiplicity distribution and nuclear effects in π−d interactions at 21 GeV/c

Results on the charged multiplicity distribution in π−d interactions at 21 GeV/c are presented. The effects due to the two-nucleon structure of the deuteron target are analysed and the contribution of double scattering processes is estimated as a function of charged multiplicity. The evidence against simple cascade models is discussed.

An impact parameter analysis of multiparticle production in medium-energy meson-proton interactions

Abstract Lower bounds can be calculated for the root-mean-square impact parameter b , in any exclusive reaction. These lower bounds, b L , have been calculated for 9 exclusive π − p reactions at 16 GeV/ c and for 24 exclusive K − p reactions at 10 and 16 GeV/ c . It is found that b L decreases with increasing multiplicity, but is larger at higher energy. The values of b L are larger for diffractive than for non-diffractive channels of the same multiplicity.

Multiplicity distributions and double-scattering effects in π−d interactions at 360 GeV/c

Abstract Double-scattering effects are studied in π − d interactions at 360 GeV/ c . The partial cross sections σ N (π − d ), σ N (“π − p ”) and σ N (“π − n ”) are presented. The double-scattering probability per π d collision is found to be ƒ = 0.15 ± 0.02 . We have extracted the partial cross section X N of the double-scattering plus interference contributions, and find that X N obeys KNO scaling. The data are compared with various theoretical predictions.

Inclusive π0 production in π+p interactions at 16 GeV/c

The inclusive γ production process π+p → γ + anything has been studied at an incident momentum of 16 GeV/c. The experimental results for γs have been used to determine the average π0 multiplicities and the cross sections for π0 production. An indirect method was used for the π0 momentum distribution. The Mueller correlation parameters ƒ2(π−, π0) and ƒ2(π0, π0) have ben determined.

Hadron production in π+ and π− neon interactions at 30 and 64 GeV/c

We report new results on charge multiplicities fromπ+ Ne andπ- Ne interactions at 30 and 64 GeV/c. The average number of fast protons is extracted and found to be essentially independent of the number of identified slow protons.

Investigation of ϱ+, ϱ− and ϱ0 production in π+p interactions at 16 GeV/c and pp interactions at 24 GeV/c and quark model predictions

Abstract Quasi-inclusive and total inclusive ϱ + , ϱ − and ϱ 0 cross sections have been studied, using data of a π + p and a pp bubble chamber experiment at 16 and 24 GeV/ c , respectively. In pp collisions it is found that the total inclusive cross sections for ϱ 0 , ϱ + and ϱ − production are about equal. This equality also holds for the differential cross sections d σ/ d y ∗ , all showing the characteristics of dominantly central production. In the π + p reactions the ϱ − are mainly produced centrally, whereas there are strong additional contributions in the beam fragmentation region for ϱ + and ϱ 0 mesons. In the central region, however, the cross sections for ϱ + , ϱ − and ϱ 0 production are almost equal within errors. All our findings agree with what is expected from quark model predictions.

High multiplicity π−d interactions at 21 GeV/c

We have studied π−d interactions at 21 GeV/c with charged multiplicities of 9 or more. Cross sections, single-particle distributions and two-particle correlations are discussed. The evidence for double scattering effects is confirmed and analysed.