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The experimental results are presented for ratios of ν-meson inclusive differential cross sections in 10.5 GeV/ c π + p, π + D and π + A collisions, R D/p =(d σ /d x F )( π + D → η X)/ (d σ /d x F ) π + p→ η X), R A =(d σ /d x F )( π + D→ η X) in the beam fragmentation region. The results are based on the statistics of ≈ 5 × 10 4 detected η → 2 γ decays. It is shown that the power α in the parametrisation R A ≈ A α ( xf ) does not change significantly with x F and its mean value is 0.50±0.02. The lower limit is obtained for the effective coefficient with string tension in the colour string model, κ ⩾ 3 GeV/fm. The observed growth of R A with x F can be explained by an assumption of a neutron halo with the factor H ≈ 4 in the nuclei.
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The inclusive production of Λ , K S 0 , Σ ± (1385) and K ∗± (892) in π − p interactions at 6 GeV/ c has been studied. The observed cross sections are: σ ( Λ )=0.94±0.06 mb, σ (K S 0 )=0.98±0.06 mb, σ ( Σ + (1385))=60±7 μb , σ ( Σ − (1385))=90±9 μ b, σ( K ∗+ (892))=216±28 μ b and σ( K ∗− (892))=41±8 μ b , respectively. The inclusive spectra of these particles are presented as functions of squared transverse momentum and Feynman scaling variable x . The polarization of Λ has also been investigated. It is found from a comparison with higher-energy data that the inclusive cross sections for Σ ± (1385) and the production ratios Σ ± (1385)/ Λ in π − p at 6 GeV/ c have not reached the high-energy limiting values.
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Cross sections have been determined for the inclusive production of vector (ϱ 0 , ω, K ∗ ) and tensor (f, A 2 ± ) mesons in p p reactions at 9.1 GeV/c for both annihilation and non-annihilation processes. Distributions in the Feynman variable x and transverse momentum squared, p T 2 , have been examined for the ϱ 0 , ω and f mesons. The slopes for p T 2 appear to be exponential and decrease with increasing particle mass for both annihilation and non-annihilation reactions, furthermore the slopes have consistently higher values for non-annihilation reactions. Comparisons with other data indicate that the ratio ϱ 0 / π − is independent of antiproton momentum in annihilation processes.
NON-ANNIHILATION EVENTS.
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The production of η(550) and ω(780) mesons is studied in π ± p interactions at 16 GeV/ c and K − p interactions at 10 and 16 GeV/ c . Cross sections for exclusive channels are presented, and for the π + p data differential cross sections are given for quasi-inclusive production where the η or ω is required to be accompanied by charged particles only. Close similarities are observed between η, ω and also ϱ 0 (770) production in terms of longitudinal and transverse variables. By a rough estimate, the η, ω and ϱ 0 inclusive yields are found to be in the ratio 0.32 : 0.85 : 1, respectively, for 16 GeV/ c π + p collisions. For non-peripheral production we estimate this same ratio to be 0.34 : 0.9 : 1.
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
DATA SUPPLIED BY A.A. LEBEDEV.
The inclusive production of Σ + (1385) and Σ − (1385) has been studied in K − p interactions at 10 and 10 and 16 GeV/ c . It is found that the cross sections for the reactions K − p → Σ ± (1385) + anything are approximately constant in the energy range form 10 to 32 GeV/ c , being ≈ 350 μ b for Σ + (1385) and ≈ 250 μ b for Σ − (1385). The d σ d p ⊥ 2 distributions for Σ ± (1385) fall off exponentially with increasing p ⊥ 2 , with sloped of about 3 (GeV/ c ) −2 . The d σ /d x distributions for Σ + (1385) and Σ − (1385) are markedly different: the production of Σ − (1385) is symmetrical forwards and backwards in the c.m.s.; for Σ + (1385), the distribution is the same as for Σ − (1385) in the forward direction, but presents a large excess of events in the backward direction. This indicates that for the production of both Σ + (1385) and Σ − (1385) the fragmentation of the incoming kaon is negligible. The fragmentation of the target proton is negligible for Σ − (1385), but it is important for Σ + (1385) and is responsible for the excess (∼100 μ b) of its cross section over that for Σ − (1385).
Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=SIG(1385P13) ,BACK=CORRECTED)//CORRECTED FOR UNSEEN DECAY MODES (PDG 1974)).
Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=SIG(1385P13) ,BACK=CORRECTED)//CORRECTED FOR UNSEEN DECAY MODES (PDG 1974)).
Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=SIG(1385P13) ,BACK=CORRECTED)//CORRECTED FOR UNSEEN DECAY MODES (PDG 1974)).
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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Inclusive cross sections and invariant single-particle distributions are presented for positive pions and protons produced in 8.05-GeV/c π−p and 18.5-GeV/c π±p inclusive reactions. Distributions in pT2 and in the longitudinal variables x, y (c.m.) and pl (lab) are shown. Comparisons are made with inclusive distributions for other particles produced in the same reactions.
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