The reactionsK−p→π∓Σ(1385)± are studied at an incident laboratory momentum of 8.25 GeV/c using data from a high statistics (≃180 events/μb) bubble chamber experiment. In the case of the reactionK−p→π−Σ(1385)+ an amplitude analysis is performed and the complete Σ(1385)+ spin density matrix is extracted as a function oft′. The results are compared with the predictions of the additive quark model. In the case of the reactionK−p→π+Σ(1385)− the cross-sections for forward and backward production are determined.
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We give the cross-sections of quasi-two-body reactions produced in K−-proton interactions at 13 different energies in the centreof-mass energy range 1.915 to 2.168 GeV.
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A description is given of an experimental study of exchange degeneracy (EXD) in hypercharge-exchange reactions using the line-reversed partners π + p→K + Σ + (K − p→ π − Σ + ) and π + p→ K + Σ + (1385) (K − p→ π − Σ + (1385)) at incident momenta of 7.0 and 10.1 GeV/ c . Both pairs of reaction were measured in the same apparatus, with particular care being taken to minimize relative normalization errors. For the Σ production reactions we present high statistics measurements of the differential cross sections and polarizations from t ′=0 to large t . The general trends of the data agree with naive expectations from weak EXD. The cross-section difference in the extreme forward direction at the higher momentum is consistent with zero and there is a general reduction in the cross-section differences going from the lower to the higher momentum. The polarizations are approximately equal in magnitude and of opposite sign between the two reactions. On the other hand, the data do not agree with the detailed predictions of EXD. The slope for the positive reaction is systematically steeper in the forward region than for the negative reaction and there is a complex s and t dependence for the cross-section differences including a cross-over at t ⋍ −0.8( GeV /c) 2 . For the Σ(1385) production reactions, we present differential cross-section measurements in the forward region (| t |<0.3(GeV/ c ) 2 ). The cross-section differences are substantial and essentially constant over the s and t ranges studied.
THESE RESULTS WERE BRIEFLY REPORTED IN A. BERGLUND ET AL., PL 73B, 369 (1978), THE RECORD OF WHICH INCLUDES THE TABULATED DATA.
THE RESULTS AT 10.1 GEV WERE FIRST PUBLISHED IN A. BERGLUND ET AL., PL 60B, 117 (1975), THE RECORD OF WHICH INCLUDES THE TABULATED DATA.
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AVERAGED OVER ALL PRODUCTION ANGLES.
We present experimental results on a number of K − p reactions at 14.3 GeV/ c that have three bodies in the final state. The final states are K − ω p , K − π p , Λπ + π − , Λ K + K − , Λp p , K ∗ − ω p , Λ(1520) K + K − and Λ(1520) p p . Whenever, with one exception explained by the Zweig rule, there is a K − or a proton in the final state, there is a diffractive-like threshold enhancement in the mass spectrum of the two recoiling particles. These enhancements account for a large fraction of the events in all but the Λπ + π − final state, where they cannot occur, and which is dominated by resonance production. We find evidence for the Q 1 (1300) decaying into K − ω .
THE DIFFRACTION DISSOCIATION CROSS SECTIONS ARE FOR DIFFRACTIVE THRESHOLD ENHANCEMENTS IN THE TWO-BODY MASS SPECTRA (WITHIN 500 MEV CM ENERGY OF THRESHOLD).
Cross sections are given for the various exclusive reactions K − p→ Λ 0 + n pions, as well as for quasi two-body final states involving ϱ 0 , ω 0 and Y 1 ∗ (1385) resonance production. The general features of Λ 0 production are presented as a function of the pion multiplicity n . Production of Y 1 ∗+ (1385) is clearly observed at all multiplicities while the Y 1 ∗− (1385) signals grow with the multiplicity, as expected in a non-exotic exchange picture. The polarisation of the Λ 0 is consistent with zero everywhere, except when it is a decay product of Y 1 ∗ (1385), when non-zero values are found for odd values of n . The reactions Λ 0 + 2π and Λ 0 + 3π are analysed in terms of the Plahte-Roberts model and good overall agreement is obtained for the various effective mass distributions and the p L ∗ , p T and cos θ distributions for the individual particles.
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We present data on K − p reactions leading to the final states K 0 n , π 0 Λ, ηΛ, η'Λ, π − Σ + , K 0 Δ 0 (1230), and π − Σ + (1385) from a bubble chamber experiment at 14.3 GeV/ c K − lab momentum. Total and differential cross sections, Λ and Σ ∓ polarisations in π 0 Λ and π − Σ + final states as well as the Σ + (1385) density matrix elements are given.
NORMALIZED TO A TOTAL CROSS SECTION OF 21.5 +- 0.2 MB (GALBRAITH ET AL, PR 138B, 913 (1965)).
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We present results on the differential cross-sections for the reactions π + p → K + Σ + (1385) and K − p → π − Σ + (1385) at 10 GeV/ c . For the first time, the same equipment has been used in measuring both reactions, in order to obtain good relative normalization. In the region of low t ( t min to −0.3 (GeV/ c ) 2 ) the two differential cross-sections have similar shape, and show a sharp forward dip indicating a dominant helicity flip contribution. However, the magnitudes of the cross-sections are significantly different, indicating substantial exchange degeneracy breaking. We find the ratio of the integrated cross-sections for the reactions K − p → π − Σ + (1385) and π + p → K + Σ + (1385) over the range −0.3 < t ′ < 0.0 (GeV/ c ) 2 to be 2.0 ± 0.2.
TMIN = -0.013 GEV**2.
TMIN = +0.012 GEV**2.
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