The ρ0-meson spin alignment is studied in p¯p interactions at 22.4 and 12 GeV/c and in the reaction p¯p→2π++2π−+neutrals at 5.7 GeV/c. An essential ρ0-meson spin alignment is observed. The values of the ρ00T element of the ρ0-meson spin-density matrix in the transversity frame are 0.56 ± 0.07, 0.53 ± 0.05, and 0.54 ± 0.04 for the above-mentioned interactions, respectively. An increase of ρ00T with ρ0 transverse momentum is obtained.
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The reactions γA→π±A* have been studied at four-momentum transfers −t<~0.5 GeV2 for seven elements ranging from hydrogen to lead. Exclusion-principle suppression is clearly visible at small-momentum transfer. Neither the A dependence nor the energy dependence of the cross sections agrees with the predictions of the vector-dominance model. The ratio of π−π+ production requires equal spatial distributions for the protons and neutrons in nuclei. Some K+ data are also presented.
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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.
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Results on multiplicities, topological cross sections, total particle production cross sections, and correlations between charged particle and π 0 production are presented for pp interactions at 12 and 24 GeV/ c incident laboratory momentum. Inclusive production of π ± , K s 0 , p , Λ, Σ ± and Λ is studied; particle spectra are shown in single and double differential form and are compared, in different kinematic regions, with data obtained at other incident momenta and with other beam particles.
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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.
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We report measurements at the CERN PS of the production cross section of J/ψ(3.1) by 24 GeV protons on hydrogen, carbon, and tungsten.
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ASSUME B.R.(E+E-) =0.069.
The reaction K + p → p + X is studied at a beam momentum of 16 GeV/ c using the events where a slow proton with momentum p lab < 1.2 GeV/ c is identified by its bubble density. The inclusive spectra presented and compared with those obtained in K + p interactions at 32 GeV/ c and K − p interactions at 14.3 GeV/ c . The prominent features associated with a triple-Regge formula are found to be consistent with the data. It is shown that the Δ ++ (1236) production strongly affects the shape of the inclusive spectra and the results of the triple-Regge fit. After removal of events associated with Δ ++ (1236) production, the data are consistent with the dominance of an ffR coupling.
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Results are presented on the inclusive π ± production in K − p interactions at 32.1 GeV/ c . The invariant longitudinal distributions have been calculated both for π + and π − in the backward c.m. hemisphere and extrapolated in the forward hemisphere under some physical assumptions. The inclusive cross sections for π + and π − amount to 32.9 ± 1.5 mb and 35.0 ± 0.7 mb respectively. The energy dependence of the inclusive pion production has been analyzed in the framework of Mueller-Regge phenomenology both in the proton fragmentation and in the central region.
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The inclusive production of K̄ ∗ (890) and K̄ ∗ (1420) is studied in K̄ − p interactions at 10 and 16 GeV/ c . At 10 GeV/ c an enhancement in the ( K ̄ 0 π − ) mass distribution is found at 1.74 GeV, but no clear signal is seen at 16 GeV/ c . The fraction of K 0 ' s coming from decay of the K ∗ (890) or K ∗ (1420) is large, being (50 ± 6)% and (45 ± 5)% at 10 and 16 GeV/ c , respectively. The inclusive cross sections for K ∗− (890) and K ∗0 (890) production are almost constant with energy from 8 to 32 GeV/ c with values of 3.5 and 3.3 mb, respectively. The K ∗ (890) production cross section is studied as a function of transverse and longitudinal variables and found to derive mainly from fragmentation of the incident K − meson. The spectra of K 0 ' s resulting from the decay of K ∗ (890) are studied.
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Inclusive production of Λ and Λ in K + p interactions is studied at incident momenta of 8.2 and 16.0 GeV/ c . Cross sections and single-particle distributions are presented, the correlation between longitudinal and transverse momentum is investigated, and the dependence of average charge multiplicity on missing mass measured. For Λ production, early scaling is observed in the target fragmentation region when the data are presented in terms of ( M 2 - M th 2 )/ s and t , where M th is the threshold value of the missing mass M . Furthermore, a triple-Regge analysis in these variable yields an effective exchange trajectory which passes through the K, Q and L mesons. There is evidence for beam fragmentation in Λ and Λ production, but the contributions seem not to be dominant in the fragmentation region. Nevertheless, the parameter values in a triple-Regge description are estimated, and together with those for target fragmentation in Λ production, provide a complete description of the fragmentation contributions to the two reactions. Integration of the resultant distribution functions over the complete Chew-Low plot yields fragmentation cross sections increasing approximately as log s ; in addition the observed features of the x , p L and p T 2 projections and of the p L - p T correlation are well-described in the fragmentation regions. Central production contributions are isolated by subtracting the calculated fragmentation distributions
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