H. Blumenfeld

Average charged particle multiplicity and topological cross sections in 50 GeVc and 69 GeVc pp interactions: Collaboration France-Soviet Union

Abstract In an exposure of the chamber Mirabelle at the Serpukhov accelerator, 1 943 interactions at 50 GeV/ c and 8 959 at 69 GeV/ c have been observed. Topological cross sections and charged multiplicity distributions are presented. The average charged multiplicities found are respectively 5.32 ± 0.13 and 5.89 ± 0.07.

Inclusive Production Cross-Sections of Resonances in 32-GeV/c K+ p Interactions

Abstract The inclusive production of resonances is systematically studied in K + p interactions at 32 GeV/ c . Total production cross sections are given for three baryon resonances, five vector and three 2 + tensor mesons. We also compare the central and fragmentation components of the total production cross sections with quark model predictions.

Λ and Λ production in K+p interactions at 32 GeV/c

Abstract A study of the inclusive and semi-inclusive Λ and Λ production in K+p interactions at 32 GeV/c is presented. The inclusive cross sections for Λ and Λ amount to 0.78 ± 0.05 and 0.42 ± 0.04 mb thus showing a remarkable growth between 16 and 32 GeV/c with a factor of 1.7 for Λ and 2.8 for Λ . Target and beam fragmentation processes are found to be dominant for Λ and Λ production respectively with the following lower limits for the corresponding cross sections: σ(p → K + ʌ) > 0.5 mb and σ(K + → p ʌ ) > 0.3 mb . Although the early scaling conditions are fulfilled for the Λ production in the target fragmentation region, and Λ production in the beam fragmentation region, scaling is not observed between 16 and 32 GeV/c in the x and pT2 Feynman variables. The Λ production is found to be very similar in the K+p inclusive reaction at 32 GeV/c and in the semi-inclusive reaction K − p → Λ K K X at the same energy. The Λ Λ pair production cross section increases significantly in K+p interactions from 16 to 32 GeV/c where it reaches the value σ Λ Λ = 47 ± 11 μ b . The cross sections for Λ or Λ produced in association with an identified proton are also given and discussed.

Study of reactions with an identified proton in pp interactions at 69 GeV/c

Abstract The reactions p + p → p + X and p + p → Δ ++ + X at 69 GeV/ c are studied in the Mirabelle bubble chamber at Serpukhov. The distribution of x and missing masses M 2 to the identified proton are shown for different topologies as well as t ′ distributions for different M 2 intervals. The cross section for the single diffractive process is evaluated. Peripheral production of a low-mass Δ ++ π − system is observed.

Neutral pion production in K+p interactions at 32 GeV/c

Abstract Inclusive and semi-inclusive distributions of γs and π 0 s in the reactions K + p → γ + X and K + p → π 0 + X at 32 GeV/ c are presented and discussed. When compared to the inclusive π − production, the π 0 cross section is found to be significantly higher in low | x | and p T regions. The data are compared with other experiments and quark fusion model predictions.

Double pomeron exchange and diffractive dissociation in the reaction pp → ppπ+π− at 69 GeV/c

Abstract We investigate the main features of the reaction pp → ppπ+π− at 69 GeV/c from data obtained in the Mirabelle bubble chamber at Serpukhov. A search for a double pomeron exchange mechanism contribution leads to an upper limit of ⋍20 μ b for M(π + π − ) ⩽ 0.7 GeV under reasonable assumptions. The four-body final state is dominated by proton diffractive dissociation p → pπ+π− (mostly Δ++π−). The cross section for this process, as well as the t production slope and the decay distributions (of the Δ++) show little variation in comparison with lower energy data.

Non-diffractive two-body channels in reactions K+p→K0π+p and K+p→K+π−π+p at 32 Gev/c

Abstract We present results on a number of non-diffractive two-body channels contributing to reactions K+p→K0π+p and K+p→K+π−π+p. The data come from an exposure of the Mirabelle bubble chamber to an r.f. separated K+ beam of 32 GeV/c at the Serpukhov accelerator. Total cross sections are given for the final states K ∗+ (890) p , K ∗+ (1420) p , K 0 Δ ++ (1232), K ∗+ (890) p , Δ ++ (1232), K ∗0 (1420) Δ ++ (1232), K ∗0 (1780) Δ ++ (1232) and K ∗0 (890) Δ ++ (1950) . The differential cross sections are given for all channels with sufficient statistics. The energy dependence of the total and differential cross sections is studied.

Lambda and anti-Lambda Production in K+ p Interactions at 32-GeV/c

Abstract A study of the inclusive and semi-inclusive Λ and Λ production in K+p interactions at 32 GeV/c is presented. The inclusive cross sections for Λ and Λ amount to 0.78 ± 0.05 and 0.42 ± 0.04 mb thus showing a remarkable growth between 16 and 32 GeV/c with a factor of 1.7 for Λ and 2.8 for Λ . Target and beam fragmentation processes are found to be dominant for Λ and Λ production respectively with the following lower limits for the corresponding cross sections: σ(p → K + ʌ) > 0.5 mb and σ(K + → p ʌ ) > 0.3 mb . Although the early scaling conditions are fulfilled for the Λ production in the target fragmentation region, and Λ production in the beam fragmentation region, scaling is not observed between 16 and 32 GeV/c in the x and pT2 Feynman variables. The Λ production is found to be very similar in the K+p inclusive reaction at 32 GeV/c and in the semi-inclusive reaction K − p → Λ K K X at the same energy. The Λ Λ pair production cross section increases significantly in K+p interactions from 16 to 32 GeV/c where it reaches the value σ Λ Λ = 47 ± 11 μ b . The cross sections for Λ or Λ produced in association with an identified proton are also given and discussed.

An analysis of K+ p interactions at 32 GeV/c in terms of “principal-axis” variables

Abstract Four- and six-body final states in K + p interactions at 32 GeV/ c are studied in terms of principal-axis variables. Evidence is found for considerable alignment of the final-state particles towards a preferred plane in momentum space. The experimental results are compared with an uncorrelated production model which, apart from the alignment effects, reproduces satisfactorily the main characteristics of the principal-axis variables. The slope of the “generalized scattering angle” distribution is found to provide information on the r.m.s. initial-state impact parameter of the reaction.

Negative pion production in proton-proton interactions at 69 GeV/c

Abstract Inclusive spectra of π − production for pp interactions are discussed at 69 GeV/ c both in the central and in the fragmentation region and are compared to data at lower and higher energies. The p T dependence of the invariant structure function is also analysed.