A study of K + p interactions at 4.6 GeV/ c leading to single-pion production is presented. Cross sections for the final states KΔ, K ∗ (891)p, K ∗ (1420)p are given. Comparison of the results of this study with published K − p and K − n data at the same momentum indicates that corresponding K − cross sections are significantly smaller, but other features such as momentum transfer distributions and density matrix elements are very similar.
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NORMALIZATION...FROM MASS-CUT BUT RENORMALIZED TO GIVE SAME INTEGERATED CROSS-SECTION AS OVERALL BREIT-WIGNER FIT.
Differential cross sections and polarizations have been measured for the reaction π − p → K 0 Λ and π − p → K 0 Σ 0 at 3.9 GeV/ c π − momentum. Comparison of these data with those of the related reactions K − n → π − Λ and K − p → π − Σ + (at approximately the same c.m. energy) indicate that simple Regge-pole models involving only K ∗ (890) and K ∗ (1420) exchange are unable to describe all the features of the data. On the other hand, comparison of the π − p → K 0 Σ 0 data with that of π + p → K + Σ + shows that the data are consistent with absence of exotic strange-meson exchange.
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Data on p p annihilations at rest into K 1 0 K 1 0 ω 0 and K + K − ω 0 are discuss New measurements for the mass, the width and the branching ratio of the ω 0 are presented. Evidence for quasi two-body annihilations p p → ϕπ, p ̄ p → S ∗ π is discussed.
PRODUCTION RATE FOR ANNIHILATION AT REST.
The reaction K + p → K ∗o (892) Δ ++ (1236) has been studied at 3 GeV/ c in both a hydrogen and a deuterium bubble chamber experiment. The production mechanism is described by a Regge-type model using π- and B-exchange. The joint decay distributions are analysed in various frames and compared with quark-model predictions.
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Resilts are reported on the four-pion final state from antiproton annihilations in hydrogen in the vicinity of 940 MeV/ c . The cross section for π − π − π + π + is found to be 3.6 mb. Abundant resonance production is observed, with fits indicating that quasi-two-body production constitutes approximately half the four-pion events. The model employed, which includes resonance production and Bose symmetrization, yields excellent fits to mass distributions and angular correlations.
ASSUMING TOTAL AP P CROSS SECTION OF 122 MB. ERRORS INCLUDE SYSTEMATIC UNCERTAINTIES.
ANALYSIS OF 4PION FINAL STATE. FIXED MASS AND WIDTH BREIT-WIGNER RESONANCES AND BACKGROUND FITTED TO DATA. CROSS SECTIONS CALCULATED BY PDG (COMPILATION PDG3). ERROR GIVEN IS SCATTER FROM VARIOUS FITS.
From a bubble chamber exposure in an antiproton beam at 5.7 GeV/ c yielding 13 events/μb, the final states p ̄ p → Y 1 ∗+ (1385)Λ, Y 1 ∗+ (1385)Σ + , Y 1 ∗+ (1385) Y 1 ∗+ (1385) have been isolated. We have measured the total cross section, d σ /d t , and the complete density matrix of the Y ∗ for these processes. Upper limits have been set to the forbidden reactions p ̄ p → Y 1 ∗− (1385)Σ − , Y 1 ∗− (1385) Y 1 ∗− (1385) .
VALUE OF PRODUCTION CROSS-SECTION IN TEXT HALVED AS INCLUDED CHARGE CONJUGATE REACTION.
VALUE OF PRODUCTION CROSS-SECTION IN TEXT HALVED AS INCLUDED CHARGE CONJUGATE REACTION.
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At 3 GeV/ c , the total and differential cross sections of the reactions K − n → Y π − have been determined for nine S = −1 baryonic states. Backward peaks associated with a dip near u = −0.2 are observed in many cases. They have been interpreted, for the isospin-zero Y-states, in terms of a proton-exchange mechanism. The backward peaks in the reactions K − n → Λπ − and K − n → Σ o π − have been more quantitatively related to the backward π N → N π differential cross sections at the same energy. This comparison leads to the conclusion, that the first reaction is dominated by nucleon exchange, whereas the second one requires a more complex exchange mechanism.
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This work extends our previous investigations at the CERN Intersecting Storage Rings, with improved statistics at three different energies, wider angular range and a better control over systematic errors. Values for the (diffraction) shape parameter b are given.
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The absolute luminosity of the CERN Intersecting Storage Rings has been determined by the Van der Meer method. Combining the measurement with small angle proton-proton elastic events, we find σ elastic = (6.8±0.6)mb.
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Using wire spark chambers we have observed the backward production of ϱ + mesons in the reaction π + p → p (missing mass) at 5.2 GeV/ c . In the four-momentum interval −0.80 < u < −0.006 (GeV/ c ) 2 the angular distribution shows a backward peak. In contrast to backward π + p elastic scattering, there is no dip in the angular distribution at u ≈ −0.15 (GeV/ c ) 2 . The ϱ + decay is found to be compatible with isotropy.
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