In a high statistics (90 events/μb) bubble chamber experiment, the reactions π − p→K s 0 K ± π ∓ n have been studied at 3.95 GeV/ c . A significant enhancement is observed in the ( K K π) system which we attribute to the production of the E(1420) meson. For its mass, M , and width, Λ, we find M =1426±6 MeV and Γ =40±15 MeV. The E(1420) quantum numbers are determined to be I G J P =0 + 1 + with a branching ratio E → K ∗ K + c.c E →[δπ+( K ∗ K + c.c. )]=0.86±0.12 , where δ→ K K . The cross section for the reaction π − p→En, with E→K 0 K ± π ± , is 8.2±1.0 μ b. Forward and backward productions are observed in the approximate ratio 2:1. The SU(3) assignment of the E(1420) meson is discussed.
BACKGROUND SUBTRACTED.
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An analysis is presented of the reaction K − p → K 0 π − p at 4.2 GeV /c incident momentum, using analytical techniques in fully dimensional phase space. This methods allows to isolate the contributions of the 0 + , 1 − and 2 + (K π ) partial waves in various helecity Separating well-understood contributions from the rest, the method is particularly useful for the detection of small effects (≈1% of the total final-state cross section) not visible in the mass distributions: (i) small cross-section contributions of 3 − (K π partial waves, K ∗ (1780), are unambiguously isolated; (ii) 3.5σ evidence is given for Σ(1480) in the (p K 0 ) system; (iii) effects due to a second K π P-wave or the possible presence of a doubly peripheral mechanism are discussed. The method furthermore allows simultaneous treatment of the (K π ) partial waves, p π ) partial waves and their interferences and of a Σ(1765) signal (with spin 5 2 ). While interferences within the (K π ) and within the (p π ) systems are strongly determining the corresponding distributions, no interference between these systems is needed.
CHANNELS CONTRIBUTING TO K- P --> AK0 PI- P. M/ETA IS ABSOLUTE VALUE OF Z-COMPONENT OF SPIN/EXCHANGE NATURALITY.
Inclusive cross sections for π 0 , K s 0 , Λ 0 and Λ 0 production in 100, 200 and 360 GeV /c π − p interactions are presented and compared with data at other energies. Invariant cross sections for γ, K s 0 , Λ 0 and Λ 0 production are presented in terms of Feynman x , the rapidity y , and transverse momentum squared, p T 2 . A comparison of the observed γ spectrum is made with the spectra computed assuming that the π 0 momentum distribution is identical to that of the observed π + or π − .
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The properties of the effect observed in the reaction p p → π + π − π + π − π 0 at 1949 ± 10 MeV /c 2 (τ ≅ 80 MeV /c 2 ) are studied. The ω 0 ϱ 0 , A 2 0 π + π − and π + π − π + π − π 0 (non-resonant) channels are found to be coupled with this object. The assignment I G = 1 − is established and an analysis of the √ s behaviour of the density matrix elements for the final state ω 0 ϱ 0 clearly favour J P = 2 + , 4 + … Comparisons are made with present theoretical schemes describing this mass region.
MAJOR CONTRIBUTION TO STRUCTURE OBSERVED AT 1949 +- 10 MEV WITH WIDTH 80 +- 20 MEV.
An experimental analysis of p p interactions between the p p threshold (√ s = 1878 MeV) and √ s = 2 100 MeV leads to clear evidence for an s -channel effect in the reaction p p → π + π − π + π − π 0 at 1949 ± 10 MeV /c 2 (Γ ⋍ 80 MeV /c 2 ) . A comparison is made with the backward elastic scattering and charge-exchange behaviour. An interpretation in terms of an object strongly coupled to mesonic decay modes, with small or middle-sized elasticity ( x ⩽ 0.135 −0.06 +0.13 ) is given. No significant narrow structure is observed in the backward elastic scattering between 1.9 and 2 GeV. The experimental resolution of √ s in this case is 2 MeV.
LOWER MOMENTUM RESULTS WERE REPORTED IN CH. D'ANDLAU ET AL., PL 58B, 223 (1975). TABULATED NUMERICAL VALUES OF DATA ON FIGURES SUPPLIED BY M. LALOUM.
K ∗0 (890) production in the hyperchange exchange reaction π − p → K ∗0 (890) Λ 0 Σ 0 at 10 GeV/ c (28 448 events) is discussed. An amplitude analysis in the t ′ range up to 1 GeV 2 shows that the production mechanism is dominated by natural parity exchange (∼84%). Comparisons are made with predictions from a Regge model and a quark model.
DENSITY MATRIX ELEMENTS IN THE GOTTFRIED-JACKSON SYSTEM ALLOWING FOR COHERENT S-WAVE BACKGROUND TO P-WAVE BREIT-WIGNER K*(892)0 RESONANCE.
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The reaction p n → p p π − at 2.98 GeV/ c is studied with high statistics. The dominant Δ −− production is found in the framework of the additive quark model to proceed mainly through unnatural parity exchange in the t -channel. A detailed comparison with the reaction K − p → K ∗0 n confirms, for the dominant part of the cross section, the predictions of the quark model.
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MIN(-T) IS 0.015 +- 0.006 GEV**2.
New results on the inclusive and semi-inclusive production of π + mesons and protons in the whole phase space are given for about 2.2 · 10 4 inelastic p p interactions at 22.4 GeV/ c . A method of statistical separation for spectra of particles of the same charge which are produced in CP -symmetrical reactions is discussed in detail. Experimental data are compared with quark-parton model predictions.
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NON-ANNIHILATION EVENTS ONLY.
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To complete data on resonance electroproduction we constructed an electron spectrometer with large angular and momentum acceptance. As a first result inclusive cross sections for an invariant hadronic mass 1.2<W<1.7 GeV and a four momentum transfer squared 0.5<Q2<1.5 (GeV/c)2 and for values of the polarization parameter 0.1<ɛ<0.25 are presented. Combining our results with the SLAC 4°-data we obtain σL/σT in the specified kinematical range.
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DATA AVERAGED FOR TWO DIRECTIONS OF TARGET POLARIZATION.
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