A. Wróblewski

General characteristics of particle production in 16 GeV/cπ−p interactions

Abstract Partial cross sections are presented for the various topologies and the various reaction channels in 16 GeV/ c π − p interactions. Their energy dependence is discussed. The distributions of events as a function of the squared four-momentum transfer are presented, as well as the transverse and c.m. longitudinal momenta distributions. The predictions of the Chan, Łoskiewicz and Allison model describe some of the gross features of these experimental results, but important disagreements are found, mostly in the low multiplicity channels.

Determination of the fire-ball dimensions from second-order interference between two pions

Abstract Positive correlations are observed for pion pairs of equal charge and similar momentum vectors, produced in the reactions π p→p+5 π and π p→p + 7 π at 4 to 25 GeV/ c . The results are consistent with being due to the second-order interference effects expected for pairs of identical bosons and lead to the determination of the average dimension of the “fire-ball’ from which the pions are emitted (〈 R 〉 = 1.0 ± −0.2 +0.4 fm). Attempts are made to study the fire-ball shape by selecting pions pair emitted in various polar and azimuthal directions.

Eta and omega meson production in medium energy π+-p and K−p interactions

The production of η(550) and ω(780) mesons is studied in π±p interactions at 16 GeV/c and K−p interactions at 10 and 16 GeV/c. Cross sections for exclusive channels are presented, and for the π+p data differential cross sections are given for quasi-inclusive production where the η or ω is required to be accompanied by charged particles only. Close similarities are observed between η, ω and also ϱ0(770) production in terms of longitudinal and transverse variables. By a rough estimate, the η, ω and ϱ0 inclusive yields are found to be in the ratio 0.32 : 0.85 : 1, respectively, for 16 GeV/c π+p collisions. For non-peripheral production we estimate this same ratio to be 0.34 : 0.9 : 1.

Strange particle production in 8 GeV/c positive pion interactions in hydrogen

Abstract Results are presented on strange particle production in 8 GeV/c π+p interactions with three and four particles in the final state. Total cross sections for different channels and for production of different resonances are estimated. Differential cross sections for quasi two-body reactions are given. Evidence is presented for the production of a (ΛK) enhancement with a mass of 1755 ± 21 MeV and a full width of 220 ± 60 MeV. Branching ratios for rare decay modes of A1, A2, fo and f′ into strange particles are given. In the ( K K π ) mass distribution possible enhancements are observed at 1490 and 1690 MeV.

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.

On Λ0 hyperons produced in K− interactions with emulsion nuclei

SummaryThe energy spectrum of Λ0 particles produced by K− interactions at rest in emulsion and found by following back stopping π−-mesons to the point of Λ0 decay has been determined. The experimentally found spectrum is corrected for systematic losses. The frequency of Λ0 emission in K− interactions and the frequency of production of cryptofragments are estimated. An analysis of other experimental results indicates that scanning biases are present in samples of Λ0 decays found in emulsion by the area-scanning technique. These biases, differing from experiment to experiment, can lead to an apparent forward-backward asymmetry in the Λ0 decay and also to an underestimation of the number of Λ0 particles emitted.RiassuntoSi è determinato lo spettro d’energia delle particelle Λ0 prodotte nell’emulsione da interazioni di K− in quiete e trovate seguendo a ritroso i mesoni π che si arrestano, sino al punto di decadimento dei Σ0. Lo spettro trovato sperimentalmente viene corretto per le perdite sistematiche. Si valuta la frequenza delle emissioni di Λ0 nelle interazioni di K− e la frequenza di produzione di criptoframmenti. Un’analisi di altri risultati sperimentali indica la presenza di errori di scanning nei campioni di decadimenti Λ0 trovati nell’emulsione col metodo di scanning per superfici. Questi errori, diversi da esperimento ad esperimento, possono portare ad un’apparente asimmetria antero-posteriore del decadimento Λ0 e anche a sottovalutare il numero di particelle Λ0 emesse.

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.

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.

Three- and four-pion angular correlations in high-multiplicity πp interactions

Abstract A new set of parameters is introduced to describe charge dependence of three- and four-pion correlations. An effect similar to the GGLP effect observed for pion pairs, but stronger, is found for three- and four-pion systems. This effect, however, can be interpreted as a reflection of the GGLP effect.