V. Grishin

Charged and neutral particle multiplicity in π−p and π−n interactions at 40 GeV/c

Abstract Data on the multiplicity of charged particles and π 0 mesons in π − p and π − n interactions are presented and compared to various models. The average π 0 multiplicity tends to increase with increasing number of charged particles.

Neutral strange particle production in π- p, π- n and π- C interactions at 40 GeV/c

Results on the inclusive and topological cross sections for Λ and K0 particles produced in π−p, π−n and π−C interactions at 40 GeV/c are reported. The σΛ(Σ0)π−p values increases twofold from 25 to 40 GeV/c while σKKπ−p increases continuously with the incident momentum. The invariant single-particle distributions in the χ and p⊥2 variables for K10 and Λ particles are presented and compared with the respective ones for π−p interactions at lower energies as well as for pp interactions at 200–300 GeV/c.

Some characteristics of inclusive reactions π-p → π± + ... and π-n → π± + ... at p = 40 GeV/c

Abstract Data on inclusive reactions π − p → π ± + … and π − n → π ± + … at 40 GeV/ c are presented. Inclusive cross sections of the reactions π − p → π ± + … at x = 0 normalized to the inelastic cross section coincide with the ISR results for pp interactions at 500 – 1500 GeV. A similar result has been obtained for the inclusive process π − p → γ + … as well.

Production of γ quanta in π−N interactions at 40 GeV/c

Data on the average multiplicity of neutral pions are presented for π−p, π−n and π−C interactions at 40 GeV/c, based on the statistics of 9 432 γ-quanta. A significant increase was found in the average number of π0s per inelastic event as a function of the number of charged particles for these interactions. Average momenta and angular characteristics of the γ-quanta are presented in both the lab. and the c.m. systems. It can be concluded that there is a plateau [in the −1<y∗<1 interval] in the (1σin)dσdy∗=f(y)∗distribution of γ-quanta for π−p interactions and the value of the π−p cross section at y∗=0 agrees quite well with the pp cross section at p=500−1500 GeV/c. This is in favour of the scaling hypothesis in the central region y∗=0 for 40 GeV/c π−p interactions.

Possible observation of medium effects using a pion correlation technique

Abstract Correlations of oppositely charged pions produced in interactions of protons and light nuclei with different nuclear targets are investigated. The invariant-mass distributions are analyzed in order to search for new conjectured nuclear effects. Strong and electromagnetic final-state interactions between pions and the Coulomb interaction between pions and the target nucleus are taken into account. An admixture of pion pairs coming from resonance decays is estimated. An enhancement in the low invariant-mass region is observed only for heavy target systems. A shadowing effect due to pion absorption inside the nuclear medium is considered as a possible source of this pattern. Azimuthal π + π − correlations and pion yield dependence on the impact parameter, as well as transport calculations, seem to confirm this assumption.

Correlations in particle production in pion-proton interactions at 40 GeV/c

Abstract Results of the investigation of some correlation effects in π − p interactions at 40 GeV/ c incident momentum are given. On the basis of 2 000 events the dependence of the transverse momenta of π + and π − mesons on the longitudinal momenta was obtained, as well as two- particle distributions for various pion pairs, and correlation functions C ( y 1 , y 2 ) and R ( y 1 , y 2 ). For π + π − pairs R (0,0) = 0.65 ± 0.07 and the correlation length is L = 1.8 ± 0.2 for −1 ⩽ y 1 , y 2 ⩽ 1. For π + π + and π − π − pairs R (0,0) = 0.26 ± 0.10. Comparison of these results with proton-proton data at 200 GeV and at ISR energies suggests that limiting behaviour in two- particle distributions R ( y 1 , y 2 ) for π − p interactions is already reached at 40 GeV.

Inclusive π−p→γ+ anything and π−12C→γ+ anything reactions at 40 GeV/c

Abstract In this paper, some results on inclusive γ and π 0 spectra in π − p and π −12 C interactions at 40 GeV/ c are reported. It is shown that there is no factorization of the structure function f ( q ⊥ , x ) in π − p→ γ + anything reactions for q ⊥ ⩽0.4 GeV/ c and | x |⩽0.16. The π 0 meson longitudinal momentum spectrum in the cms is obtained by applying the method of statistical regularization to the measured γ spectrum. In the range | x |⩽0.02, N π + = N π − = N π 0 within the error limits (±7%). The inclusive γ spectra in π − p and π −12 C interactions indicate that the normalized structure function is the same for both reactions over the central and the π − meson fargmentation regions.

Inclusive two-particle correlations in 40 GeV/c π−p collisions and particle production mechanisms

Abstract Inclusive two-particle correlations in rapidity variables between π + π − , π + π + and π − π − obtained in 40 GeV π − p collisions are discussed in the framework of the Mueller Regge model and the multiperipheral cluster model. The data show features similar to the data reported at much higher energies from the CERN ISR. This behaviour is more easily understood from the multiperipheral cluster model. Data on transverse momentum correlations in the same reactions can be qualitatively understood from the same model.

Direct pair production by charged particles at 4 GeV/c in a propane bubble chamber

Abstract The direct electron pair production by pions, muons and electrons at 4 GeV/ c has been investigated in a propane bubble chamber. The experimental results have been found within the 30% in agreement with the cross sections calculated by Bhabha and Murota, Ueda and Tanaka. A special method of the background subtraction has been developed. The method is very convenient for the investigation of the production of electron pairs by electrons in a hydrogen bubble chamber.

On the minimum number of partial waves in two-body reactions

Abstract A reliable method is offered to determine the minimum number of partial waves involved in the interaction, if the total elastic cross section and differential cross section at a given angle are known.