N.N. Melnikova

Interaction cross sections and negative pion multiplicities in nucleus-nucleus collisions at 4.2 GeV/c per nucleon

Scanning results ofp, d, he, and12C interactions on Ta plates and in propane are presented. Inelastic cross sections are determined. They agree with geometrical models. General characteristics of pion multiplicity distributions are analyzed and compared with results from nucleon-nucleon interactions. Average multiplicities of negative pions are found to depend on the number of interacting beam nucleons.

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.

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.

Scaling of semi-inclusive cross sections with respect to longitudinal and transverse momenta

Abstract The semi-inclusive one-particle transverse and longitudinal momenta spectra of π ± mesons have been studied in the centre-of-mass system for π − p interactions at 40 GeV/ c . These data are compared with similar data from pp interactions at 300 GeV/ c and lower energies. Distributions in the variables p T /〈 p T 〉 and p L /〈 p L 〉 reveal scaling properties, which are found to be substantially independent of the nature of the projectile, of the incident energy and of the prong multiplicity. These spectra are reasonably described by universal functions.