A partial-wave analysis of the K 0 π + π − system from the reaction K − p → K 0 π + π − n has been carried out using data obtained at 8.25 GeV/ c in a high-statistics experiment. A strong signal appears in the 1 + SO + (K ∗ π) wave at the Q 2 mass (≈ 1.4 GeV). The 1 + S0 + (ϱK) wave behaves rather like a background and does not exhibit the characteristics of a resonance. A prominent signal also appears in the 2 + D wave (via K ∗ π and ϱK); it is interpreted as the K ∗ (1430). In the L region (1.6–2.1) GeV, there is evidence for the 3 − K ∗ (1780) while the 2 − wave also gives some contribution.
FULLY CORRECTED CROSS SECTION.
RESONANCE FITS CROSS SECTIONS USING BREIT WIGNER FUNCTION. NOTE THAT FOR THE K*(1780) THE CROSS SECTION DETERMINATION IS STRONGLY DEPENDENT ON THE BACKGROUND ASSUMED WHICH HAS BEEN ONLY SUBTRACTED AT 8.25 GEV.
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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Inclusive Λ production has been studied in K − p interactions at 8.25 GeV/ c using about 69 000 events; the total cross section is found to be 3.35 ± 0.20 mb. A comparison has been made with Σ 0 and Σ(1385) inclusive production. Their influence on the inclusive Λ production is discussed. The inclusive Λ cross section and polarization is interpreted in terms of the triple-Regge model. In the target fragmentation region an effective Regge trajectory is determined which lies closer to the K than to the K ∗ . In the beam fragmentation region the cross-section data indicate an effective Regge trajectory which corresponds to the nucleon, while the polarization data require additional Regge exchanges to be present.
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The dissociation of a K− into the K−ϕ system is studied at 8.25 GeV/c. The cross-section for K−ϕp production is (27±2) μb. All the expected properties of diffraction are found (mass spectrum, mass-slope correlation, 1+S wave dominance). There is also an indication of the Kϕ decay mode of a 2− resonance in theL region.
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Differential cross sections and polarizations are presented for the reactions K − p → Λπ 0 , Λη , Λη ′ at 8.25 GeV/ c incident K − momentum. The data, which come from a high statistics experiment in the CERN 2 m bubble chamber, are compared with previous experimental results on the same reactions and with current theoretical ideas.
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Inclusive Ξ − production is studied in K − p interactions at 8.25 GeV/ c using about 8000 events. An analysis based on the triple-Regge model shows that the Λ α − Λ γ and Σ β − Σ δ exchanges explain the forward Ξ − production. Ξ(1530) properties are also studied and are found to be similar to those of Ξ − 's. Finally, a study of the production of Ω − based on 67 events shows that Ω's are also produced by hyperon exchange.
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In a high statistics ( ∼150 eV μb ) bubble chamber experiment on K − p interactions at 8.25 GeV c , the study of the reaction K − p → KK Λ provides evidence for an enhancement in the KK system with a mass of (1850 ± 10) MeV and a width of (80 −30 +40 ) MeV. Its possible identification with the missing isosinglet of the 3 − nonet is discussed. A K ∗ K decay mode is also observed.
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In a high statistics bubble chamber study the reaction K − p → φφΛ is detected with a cross section of 0.7±0.2 μ b. The ratio of φφ production in K − and π − induced reactions is found to be ∼5; this is about ten times smaller than the ratio for the corresponding single φ production reactions.
CORRECTED FOR UNSEEN DECAY MODES OF LAMBDA AND PHI.
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We observe production of a Ξ * (2370) in the reactions K − p→ [YK¯π] K, [YK¯π] Kπ and [ΩK] (K or Kπ) at 8.25 GeV/ c in a high statistics bubble chamber experiment. The mass and width are determined to be 2373 ± 8 MeV and 80 ± 25 MeV, respectively. The I = 1/2 assignment is strongly favoured.
CROSS SECTIONS FOR PRODUCTION OF XI(2370) --> (LAMBDA + SIGMA) AK PI. BREIT-WIGNER FIT WITH POLYNOMIAL BACKGROUND. XI(2370) PRODUCED BY BARYON EXCHANGE. CORRECTED FOR NEUTRAL DECAYS AND GEOMETRICAL LOSSES. <OMEGA-KAON> DECAY SEEN. OBSERVED RATIO OF CHARGED TO NEUTRAL XI(2370) PRODUCTION IS 2.7 +- 0.9.
We present evidence for a narrow Y ∗ with a mass of 3.17 GeV and a width ⩽ 20 MeV decaying to ΣKK̄ + pions, ΛKK̄ + pions and ΞK + pions. The data come from two high statistics K − p bubble chamber experiments with a sensitivity of ≈100 eV/ μb at 8.25 GeV/ c and ≈ 45 eV/ μb at 6.5 GeV/ c .
OBSERVATION OF R(3170) ONLY DECAYING INTO 5 OR 6 PARTICLES (CROSS SECTION NOT CORRECTED FOR DECAYS WITH MORE THAN ONE UNSEEN FINAL STATE PARTICLE).