D. E. Plane

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.

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 Energy calibration of LEP in the 1993 scan

This report summarizes the procedure for providing the absolute energy calibration of the LEP beams during the energy scan in 1993. The average beam energy around the LEP ring was measured in 25 calibrations with the resonant depolarization technique. The time variation of this average beam energy is well described by a model of the accelerator based on monitored quantities. The absolute calibration of the centre of mass energies of the off-peak points is determined with a precision of 2 parts in 105 resulting in a systematic error on the Z-mass of about 1.4 MeV and on the Z-width of about 1.5 MeV.

Stray baryonic resonances and SU(3)

Abstract We attempt to accommodate into SU(3), on the basis of their decay rates, those baryonic resonances which are presently without definite multiplet assignments. It is shown that for a large fraction of them no SU(3) companions have yet been found. Certain regularities are however noted for most of the remaining resonances which are successfully accommodated in the scheme.

Measurement of the lifetimes of the Σ± hyperons and of the branching ratio of the non-leptonic Σ+ decay

Abstract The measurements have been done using about 20,000 reactions K−p→Σ±π± with K− momenta from 400 to 1200 MeV/c and give τ + = (0.803 ± 0.008) · 10 −10 sec. τ − = (1.472 ± 0.016) · 10 −10 sec and R = (Σ + → n π + ) [(Σ + → n π + ) + (Σ + → p π 0 )] = 0.488 ± 0.010 . The result for τ− is in serious disagreement with the generally accepted value.

Decay modes of ∑(1660)

Values are given for the branching fractions of various decay modes of the hyperon resonance ∑(1660). The measurements were obtained in formation experiments of the type K−p→∑(1660) → KN, ∑π, Δπ, ∑ππ and Δππ.

Search for long-lived particles in 200 GeV/c proton-nucleon collisions

A search for long-lived particles (τ ≳ 10−8 sec), with changes ±23, ± 1, ±43 and ± 2, produced in 200 GeV pN collisions was performed at the CERN-SPS in a secondary beam equipped with superconducting r.f. separators. Upper limits were obtained for the production of long-lived hadrons and leptons. For charge - 1 particles the limits are at the level of 10−7 of the pions at a mass m = 0.2 GeV and reach the 10−11 level from 3 to 8 GeV. The production of light antinuclei was measured. The cross sections for 3He production are (1.3 ± 0.3) and (1.9 ± 0.3) × 10−34 cm2/sr · GeV/c at 21 and 47.4 GeV/c respectively; for t the cross section is (7.6 ± 0.9) × 10−34 cm2/sr · GeV/c at 23.7 GeV/c.

Dual features of KN elastic scattering amplitudes

The conjectures of Freund and Harari, together with s-channel helicity conservation in diffraction are shown to stand the tests now available in the KN channel. The relevant amplitudes were obtained through a partial wave analysis in the c.m. energy range from 1.55 to 2.14 GeV. Some evidence for the existence of P01 and S11 resonances is discussed.