Transverse momentum distributions of λ o , λ o , and K o , produced in pp collisions at x = 0, have obtained at the CERN ISR. The K o yield is in agreement with published K + , K − results, obtained at this centre-of-mass energy (√ s ≈44 GeV). The results on λ o and λ o production obtained in this experiment are compared with results obtained at lower centre-of-mass energies.
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From the reaction π−n→pπ−π−π0 at 9.140 GeV/c the Δ0ϱ− reaction has been selected. The upper limit in the cross-section ofμb
A SMALL CORRECTION FOR THE DEL0 TAIL IS NOT PERFORMED.
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The backward elastic scattering reaction π − p → p π − at momenta 25 and 38 GeV/ c have been measured using a magnetic spectrometer with hybrid chambers. The experimental data on the dependence of the cross section d σ /d u on the momentum transfer u as well as the energy dependence d σ /d u at u = 0 are given.
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The inclusive production of π and η mesons at 90° from proton-proton collisions has been measured at the CERN ISR at centre-of-mass energies between 23.5 and 62.4 GeV. The momentum correlation of charged particles emitted together with a large transverse momentum pion has also been studied, using two magnetic spectrometers each centred at 90°.
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A measurement of the cross section of the charge-exchange reaction pp→ Δ ++ (1232)n at √ s = 23, 31 and 45 GeV at the CERN-ISR is reported. The energy dependence continues to follow a power law p lab − n with n = 1.94 ± 0.03 indicating dominance of one-pion exchange at the lowest ISR energy; there is some evidence for deviation from this at the higher ISR energies.
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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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Proton polarization in γd→pn has been measured at c.m. angle around 90° and photon energies from 325 to 725 MeV. The polarization increases sharply with the photon energy, reaching a high maximum of (-80±8)% around 500-550 MeV. Such a high polarization with a sharp energy dependence seems to indicate a new effect in the dibaryon system.
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The production of the f 0 (1270) has been studied in the reaction π − p → π + π − n at 12 and 15 GeV/ c in the momentum transfer range 0.02 to 0.80 GeV 2 . Differential and total cross sections for the reaction π − p → f 0 n have been determined. The f 0 decay density matrix elements have been evaluated requiring all the matrix eigenvalues to be non-negative. The relative unnatural and natural parity exchange contributions to the f 0 production have been studied. The results are compared with a Regge exchange model formulated in terms of the pion and A 2 exchanges including cut contributions.
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The Split Field Magnet facility at the CERN ISR has been used to measure inclusive resonance production in inelastic p-p collisions at a c.m. energy of 53 GeV. The mass spectrum of pairs of oppositely charged hadrons shows a strong correlation, which can be explained as a consequence of dominant vector meson production, accounting for more than 60% of all pions and kaons produced.
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A spin-parity 1 + ϱπ enhancement is observed for the 3π mass spectrum in the reaction K − p → Σ − π + π + π − where events with a small (K − → Σ − ) momentum transfer are selected. The mass (1040 MeV) and width (230 MeV) of this enhancement are reminiscent of the A 1 → ϱπ bump which has mainly been observed in the diffractive-like processes. The cross section for this enhancement at 4.15 GeV/ c incident K − momentum is (3.6 ± 0.5) μ b.
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