The four-pion final state in pp annihilations at 5.7 GeV/c

577 events from $\text{p}\text{p}\text{→2π}{}^{\mathrm{+}}\text{2π}{}^{\mathrm{?}}$ annihilations at 5.7 GeV/c are analyzed. Single-particle spectra are studied and an effective matrix element in the form Π_i=1⁴ exp(?Bp_Ti²) is determined. The rates for production of ?° and f⁰ mesons are estimated and the influence of resonances on the angular distributions of pions and dipions is investigated. Transverse momenta correlations can be explained using peripheral phase space.     

CO adsorption on Pd particles: TDS studies

Experimental results which concern a CO adsorption process on small Pd/mica particles are presented. The carbon blocking of adsorption sites on the Pd surface during CO desorption is demonstrated. Measurements under UHV conditions confirm the existence of saturation of this process. The associative CO desorption peak following the previous CO decomposition has been observed.     

Observation of the spin alignment of the ϱ0-meson produced in ¯pp interactions at 22.4 and 5.7 GeV/c

Studying the ⁰-meson production in ¯pp interactions at 22.4 GeV/c and in 4-prong anníhilation channels of ¯pp interactions at 5.7 GeV/c, we have observed an essential ⁰-meson spin alignment. The values of the ₀₀ element of the ⁰-meson spin density matrix (thez-axis is directed along the normal to the production plane) are equal to 0.08 ± 0.07 and 0.55 ± 0.03, respectively, i.e. the ⁰-meson spin lies preferably in the production plane. The absence of such an effect in pp interactions at 12 and 24 GeV/c and also the essentially larger ⁰ production cross section in ¯pp interactions at these energies make it possible to connect the observed ⁰-meson spin alignment with the annihilation processes. The character of the observed spin alignment is unexpected from the point of view of usual models, e.g. multiperipheral models. This effect could be described by the spontaneous polarization of quarks and antiquarks during the state preceding their recombination into mesons.Dedicated to Professor Ivan Úlehla on the occasion of his sixtieth birthday.The authors would like to express their gratitude to the CERN-Prague collaboration for permission to use their data on ¯pp interactions at 5.7 GeV/c. The authors are also indebted to A. M. Baldin, S. B. Gerasimov and H. I. Miettinen for valuable discussions, to the technicians and assistants at all laboratories for their work.     

тРЕхлУЧЕВыЕ ВжАИМОД ЕИстВИь π−-МЕжОНОВ с ИМпУльсОМ 4 GeV/c В пРОпАНОВОИ пУжыРь кОВОИ кАМЕРЕ

Altogether 1648 cases of three-prong interaction of ^–-mesons with a 4 GeV/c impulse were found on 90 000 pictures from a propane bubble chamber 55 × 28 × 14 cm³ in size; all three secondary particles were pions, two having a negative and one a positive charge. Analysis of these cases showed that at an impulse of 4 GeV/c of primary ^–-mesons the process of the coherent production of pions was not observed. On the other hand, this analysis led to an interesting result: (19 ± 9) % of the total number of (⁺, ^–) pairs in A interactions is due to the decay of the meson ^{0 +} + ^–. A value of = (764 ± 36) MeV was obtained for the mass of mesons and = (166 ± 55) MeV fort he width of its resonance curve. Investigation of the distribution of masses in the case in question gave no answer due to the insufficiently determined course of the background curve.

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On leave from:Institute of Physics, Czechosl. Acad. Sci., Lumumbova 1, Praha 8, Czechoslovakia.

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Joint Institute of Nuclear Research, Dubna, USSR.

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Institute of Physics, Czechosl. Acad. Sci., Lumumbova 1, Praha 8, Czechoslovakia.

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Faculty of Mathematics and Physics, Charles University, Brehová 7, Praha 1, Czechoslovakia.

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