A study has been made of the individual channels that contribute to the reaction K − p → Λ 0 + neutrals in the K − momentum range from 525 to 820 MeV/ c . Total cross sections are presented for the K − p → Λ 0 η 0 , Σ 0 Σ 0 π 0 , Λ 0 π 0 , Σ 0 π 0 and Σ 0 π 0 π 0 channels and differential cross sections for K − p → Λ 0 π 0 . The data were obtained in a heavy liquid bubble chamber experiment with an average gamma detection efficiency of 70%. Only events with all decay gammas detected were used for analysis. This is the first of a series of papers on this subject and presents the experimental technique in detail.
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TWO EVENTS SEEN WITH MASSES 800 +- 90 MEV AND 1400 +- 90 MEV. THE FIRST WHEN INTERPRETED AS ETAPRIME PRODUCTION GIVES A WIDTH OF 11, +15, -8 KEV FOR ETAPRIME --> 2GAMMA USING THE EQUIVALENT PHOTON APPROXIMATION.
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APPROXIMATELY CONSTANT MOMENTUM TRANSFER.
The results presented in this paper are obtained from an analysis of bubble-chamber pictures of K−d interactions at an incident K− momentum of 5.5 GeV/c. Generally, the quasitwo-body final states are produced peripherally, with a small backward peak occurring in some of the final states. The final states Σ−ω, Σ−ρ0, and Σ−φ appear to be produced primarily by vector-meson exchange. In the final state Λ(1520)π− the decay distributions of the Λ(1520) hyperon are found to be consistent with a vector-exchagne production process with M2 coupling at the nucleon vertex. The predictions of the independent-quark model and of other symmetry schemes, namely that the forward cross sections for Σ−ρ0, Σ−ω, Σ−φ production be in the ratios 1: 1: 2, are not inconsistent with our experimental values.
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FRACTIONAL FORWARD HYPERON CROSS SECTION AFTER BACKGROUND SUBTRACTION.
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Final results for 3678 six-prong π+p events at 8 GeV/c are presented. Single-particle distributions are compared with the predictions of the Chan-Loskiewicz-Allison model and the phenomenological model of the F(t) function. Differences between the transverse momenta of the π+ and π− and between the transverse momenta of secondaries emitted forward and backward in the c.m. system are observed. Cross sections for production of the ρ0, ρ+, ρ−, η, ω0, X0, and D0 mesons and the N33*++ and N33*− isobars are given, together with upper limits for some other resonances. The D0 meson is observed in the seven-body channel in the ηπ+π− system, with some evidence for the cascade decay D0→δ±π∓→ηπ+π−. The branching ratio (f0→2π+2π−)(f0→2π) is determined to be (2.2−2.2+4.5)%. Upper limits for the decay of A mesons into X0π systems are quoted. The cross section for the two-body reaction π+p→N33*++X0 is determined to be 30 ± 13 μb, from which the η0−X0 mixing angle is derived. Associated production of N33*++ and ρ0 in the six-body channel and of N33*++, ρ0, and ω0 in the seven-body channel is studied, and the cross sections for reactions involving simultaneous production of these resonances are estimated. The Goldhaber-Goldhaber-Lee-Pais effect is studied and shown to be strong in the six-body channel, especially for selected events with low energy of the pion system.
TOTAL NUMBER EVENTS=504. DATA FROM T 1.
TOTAL NUMBER EVENTS=1075. DATA FROM T 1.
TOTAL NUMBER EVENTS=425. DATA FROM T 1.
In a study of the production mechanism of quasi-two-body final states at the five incident π+ momenta 2.95, 3.2, 3.5, 3.75, and 4.08 GeV/c, approximately 40 000 events with four outgoing charged particles were investigated. The cross sections for the processes π+p→N*++ρ, π+p→N*++ω, π+p→N*++η, and π+p→N*++f have been measured as a function of the pion energy. The differential cross sections and the decay density-matrix elements are discussed in terms of one-meson-exchange models [with absorption (OPEA) and with form factor (OPEW)] and Regge models. For the N*++ρ and the N*++ω reactions, the joint-decay matrix elements are calculated. The formation of N*(2850) in the direct channel is also investigated.
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We give new experimental results on ρω interference and two-body cross sections in p¯p annihilation at 2.3GeVc. These are used, together with ρω interference results from lower energies, to argue that the annihilation process is not mediated by discrete s-channel mesonic resonances in the mass range 2.1-2.6 GeV.
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A study is made of η 0 production in p p → 3π + 3π − π 0 (7500 events) at an incident momentum of 720 MeV/ c . The reaction is dominated by production of ω 0 (≈68 o/o). The η o production has been studied by means of two independent methods: the first, a study of correlations between the (4 π ) ± and (5 π ) 0 and the (3 π ) 0 systems, circumvents the problem of ω 0 reflections. The second attempts to isolate the η 0 4π channel by means of rigorous selections using the decay properties of η 0 and ω 0 . The results of the two methods are consistent and confirnm the production of σ +- , D 0 and E 0 with the decays ifD 0 → σ ± π ± → η 0 π + π ( su −), E 0 → σ ± π ∓ → η ( su 0) π + π − , E 0 → η 0 π + π − .
CORRECTED FOR UNOBSERVED ETA DECAYS AND I=0 ASSUMED FOR ETAPRIME, D(1285) AND E(1420) --> ETA PI0 PI0.
Lambda production is studied in K − p interactions at 10.1 GeV/ c , where the dominant reaction is K − p → Λ + pions. General characteristics such as the distributions of the double differential cross section in the lab system, of the variable x = p L ∗ p max ∗ , of p ⊥ 2 and of the missing mass to the lambda are presented. Total cross sections for Λ production and for the various channels are given. Differential cross sections d σ d t , d σ d t′ and d σ d u′ are presented. Forward and backward peaks are observed in the d σ d t′ and d σ d u′ distributions, respectively. It is found that the exponential slope of these distributions decreases with increasing missing mass to the lambda and, for d σ d t′ , also for increasing multiplicity in the final state. The polarization of the lambdas is studied as a function of multiplicity, p L ∗ , (Λπ ± ) effective mass, t ′ and u ′. The forward lambdas show
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POSSIBLE FORWARD DIP.
Approximately 21 000 four-prong pp interactions at 13.1 GeV/ c have been studied using the CERN 2m hydrogen bubble chamber. The following reactions have been analyzed pp→ppπ + π − (1) pp→ppπ + π − π 0 (2) pp→ppπ + π + π − (3) The Δ-production is the dominant feature. We also observed the pππ decay of the N ∗ (1470) and N ∗ (1690). The ϱis weakly produced in the three reactions. The η and the α are observed in the reaction (2) and the presence of a ω isobar is discussed. Then the kinematical characteristics of the final particles are described.
NORMALIZED TO A TOTAL CROSS SECTION OF 39.6 +- 0.2 MB.
RESONANCE PRODUCTION ESTIMATED BY CUTS WITH MONTE-CARLO AND HAND-DRAWN PHASE SPACE DISTRIBUTIONS.
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