Search

Inclusive cross sections and longitudinal momentum distributions are presented for γ rays produced in K−p and K+p interactions at 32 GeV/c in the 4.5 m Mirabelle hydrogen bubble chamber at the Serpukhov accelerator. The average longitudinal and transverse momentum of neutral pions and the average π0 multiplicity 〈n π0〉 are estimated. It is found that 〈n π0〉 is an increasing function of the number of charged prongs.

Inclusive production of vector and tensor mesons is studied in a K−p experiment at 32 GeV/c in the MIRABELLE bubble chamber. The K∗0(890), ϱ0 and ω cross sections are comparable, about 4 mb each. The K∗0(1420 and cross sections are also comparable, about 1 mb each. The K∗o+(890), Φ, K∗o−(1420) and f cross sections beam fragmentation; ϱ production is almost forward-backward symmetric in the c.m.s. The pT production slopes of K∗o−(890) and ϱ are similar, the Φ slope is shallower. Vector and tensor mesons alone are responsible for ≅50% (≅60%) of final-state pions

The average charged particle multiplicities, 〈 n R ( M X 2 )〉, in the reactions K + p → π − X and K + p → K 0 X at 32 GeV/ c are studied as functions of the mass squared M X 2 of the “associated” system X. A comparison with the corresponding results obtained at lower incident momenta is presented.

We present a systematic investigation of channel cross sections in K−p interactions at 32 GeV/c. The energy dependence of these cross sections is discussed. We also investigate a few non-diffractive two-body reactions. The total cross sections of the two reactions K−p→K∗−(890)p and K−p→K∗−(1420)p have a markedly different energy behaviour. There is clear evidence for the reaction K−p→K∗0(890) N0(1688); its differnttial cross section exhibits a sharp forward slope of 24 ± 3 GeV−2.

The cross sections of several exclusive reactions in p p interactions are given. In the channels p p → p p π + π − and p p → p p 2π + 2π − which dominate the interactions, the single and double diffractive dissociations are analysed and compared to the results obtained with K±p interactions at the same energy, pp and p p interactions at other energies. The test of factorization at the p → pπ+π− vertex is well verified. The process p p → Δ ++ Δ ++ is studied and the cross sections of Δ ++ , Δ ++ , ϱ 0 and f 0 production are also given.

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.

The Bose-Einstein interference effect between pions of equal charge has been studied in K+p reactions at 32 GeV/c. These correlations were analysed in the framework of the Kopylov-Podgoretski-Cocconi model. The values obtained for the Kopylov parameters lie in the range of 0.8 to 1.0 fm forR, a measure of the dimensions of the pion source, and 1 to 2·10−24 s for τ, a parameter characteristic for the time evolution of particle production. The data also indicate that only a fraction λ, between 30 and 60%, of the pions interferes. The parametersR and τ show no variation with charged multiplicity, whereas λ decreases when the number of charged particles increases.

The inclusive production of protons with laboratory momentum less than 1.2 GeV/ c is studied in the reacion K + p → pX at 32 GeV/ c . A comparison with the 16 GeV/ c data shows ahat the total cross section remains practically constant while the structure function shows a clear energy dependence. The data are compatible with a tripls-Regge expansion and with factorization. About 40% of the events include a K 0 in the final state. The analysis of the K 0 pX sample indicates a sizeable contribution of beam fragmentation and abundant K 890 ∗ and Δ ++ production.

Inclusive cross sections and one-particle inclusive spectra are given for neutral K, Λ and Λ produced in K − p and K + p interactions at 32 GeV/ c in the 4.5 m Mirabelle hydrogen bubble chamber at the Serpukhov accelerator. Cross sections for associated production are also given, and the energy dependences of the cross sections and of the x distributions in the central and in the fragmentation regions are discussed.

Topological cross sections are presented for K+p, K−p and p p interations at 32 GeV/c and for π+p and π−p interactions at 50 GeV/c observed in the 4.5 m Mirabelle hydrogen bubble chamber at Serpukhov. Parameters characterizing the behaviour of the multiplicity distributions, namely 〈nc〉, D and f2 and the normalized moments are given. The dependence of these parameters on the energy and the nature of the beam particle is discussed. The multiplicity distributions obtained cannot be described by a single function in the KNO variables.

Inclusive and semi-inclusive distributions of γ's 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.

Inclusive ϱ 0 and φ production is investigated in K + p interactions at 32 GeV/ c . Total and semi-inclusive ϱ 0 and φ cross sections, longitudinal and transverse momentum distributions, including 〈 P T versus x dependence are presented. No evidence for a sea-gull effect is observed. Comparison with quark models strongly suggests the possibility that a large fraction of the ϱ 0 and vector mesons are produced as fragmentation products of the incident particles. Study of uncorrelated π + π − pairs in the ϱ 0 mass range provides possible indirect evidence for the existence of diquarks in the proton.