E. Burkhardt

K−p cross sections from440 to 800 MeV/c

Abstract K − p reactions have been studied at 19 different momenta between 436 and793 MeV/ c . This interval corresponds to a mass of theK¯N system from 1535 to 1695 MeV. About 400 000 photographs were taken in the 81 cm Saclay hydrogen bubble chamber exposed to a separated K − beam at the CERN proton-synchrotron. A total of about 100 000 events were analysed, from which partial and differential cross sections were determined. Polarizations were obtained for the two-body reactions where the decay of the Λ or Σ hyperon allowed their measurement. Data for all the channels are presented here.

A fit of baryon decay rates within SU(3)

Abstract A test of the consistency between observed resonant amplitudes or decay rates for baryon resonances with SU(3) predictions has been made. Coupling constants describing the decays are determined and predictions are given for decays into stable baryons and mesons.

The reactions K−p → K−p and K−p → Kon between 600 and 1200 MeV/c

Data on K−p → K−p, K− → Kon and on the K−p total cross section between 600 and 1200 MeV/c are analysed in terms of resonant and non-resonant partial-wave amplitudes.

Energy-independent partial-wave analysis of KN → Λπ between 600 and 1200 MeV/c

Abstract The reactions K−p → ΛπO and K−n → Λπ− in the centre-of-mass energy range from ≈1.6 to ≈1.9 GeV have been interpreted in terms of an energy-independent partial-wave analysis. Solutions are presented and the possible existence of new resonant states is discussed.

New experimental results on the reactions K−p → KN and K−p → Σπ and a partial-wave analysis between 430 and 800 MeV/c

The reactions K−p → K−p, K0n and K−p → Σ+π−, Σ0π0, Σ−π+ have been studied in the c.m. energy range 1530 – 1700 MeV; new experimental data are presented and results of an energy-dependent partial-wave analysis are discussed.

The KN interaction from 800 to 1200 MeV/c (II) K−p and KNπ final states from an analysis of two-prong events

The reactions of K−p → K−p and K−p → KNπ have been studied at 24 momenta between 777 and 1226 MeV/c. For this purpose about 71 000 two-prong events were analyzed, from photographs taken in the 81 cm Saclay hydrogen bubble chamber, exposed to a separated K− beam at the CERN proton synchrotron. Presented here are the partial and differential K−p → K−p cross sections together with a detailed description of the experimental procedure adopted in their determination. The analysis of resonance formation in K−p → KK previously reported has been updated using these new K−p → K−p data. Cross sections for K−p → K−pπ0, K−nπ+, K0pπ− are also given. The analysis of resonance production and formation for these channels will, however, be reported elsewhere.

Analysis of the reaction np → dπ+π− below 3.5 GeV/c

Abstract The reaction np → d π + π − was studied from threshold up to 3.5 GeV/ c neutron beam momentum. Cross-section values for this reaction are evaluated as a function of the beam momentum. The deuteron production features and the enhancement observed in the dπ mass spectrum at 2.17 GeV are adequately described in terms of an OPE model and nucleon-nucleon final-state interactions.

An improved partial wave analysis of KN → KN from 800 to 1200 MeV/c

An extensive search for resonant states has been performed through an energy dependent partial wave analysis of KN data in the momentum region 777 – 1226 MeV/c. The K−p → K−p, KOn differential cross sections, polarization angular distributions and total K−p cross sections were included in the fit. In addition to the well established hyperons, evidence is reported for a resonant state Σ(1760) of JP=12− and for the assignment JP=32+ for a Λ(1870) state previously assigned to JP=72+. From the K−p differential and total cross sections between 436 and 1226 MeV/c the ratio of the real to the imaginary part of the forward scattering amplitude has been derived as a function of K− incident momentum. These results are found to be consistent with the predictions of several dispersion relation calculations.

Partial-wave analysis of the reaction K−p → Σπ between 0.6 and 1.0 GeV/c

Abstract Data on the reactions K−p → Σπ are analyzed in terms of partial-wave amplitudes. Results are presented on resonance formation in the mass region 1.6 to 1.8 GeV.

The KN interaction from 800 to 1200 MeV/c (III) a study of Λ(1520)

Abstract The resonant parameters of Λ(1520) have been determined from an analysis of the reaction sequence K − p → Σ (1760) → Λ (1520) π 0 with subsequent decay of Λ(1520) into K − p, Σ ± π ∓ and Λπ + π − . The best values for the Λ(1520) mass and width are: E R = 1517.2 ± 0.6 MeV. Γ = 14.7 ± 1.8 MeV. Its decay branching ratios are Γ(Σπ)/Γ( K N ) = 0.82 ± 0.08 and Γ(Λππ)/Γ( K N ) = 0.22 ± 0.03 and its branching fractions Γ( K N )/Λ = 0.49 ± 0.02, Γ(Σπ)/Γ = 0.40 ± 0.02. Γ(Λππ)/Γ = 0.11 ± 0.01 .