Abstract:

We describe the calibration of a large 60 element neutron counter with a threshold of 2.7 MeV equivalent electron energy. The performance of the counter has been measured in the neutron kinetic energy range 8.5-430 MeV using a neutron beam at the CERN Synchrocyclotron. The results obtained for the efficiency as a function of energy are in reasonable agreement with a Monte Carlo calculation. © 1978.

Abstract:

Data on the reaction π-p → π+π-π0 have been taken at 12 and 15 GeV/c with the CERN Omega multiparticle spectrometer. In a 3-pion partial-wave analysis strong production of A20 (1310) and ω* (1675) is observed. Total and differential cross sections are determined and density matrix elements presented as a function of t in the t- and s-channel frames. The energy dependence of A20 production is studied, and a comparison of ω(780), A20(1310) and ω* (1675) production is made. © 1978.

Abstract:

An experiment has been performed on the Omega spectrometer to study the channel π-p → π+π-n at 12 and 15 GeV/. The π+π- angular distribution has been studied in the π+π- invariant-mass region 0.8-2.2 GeV/c2, for events with four-momentum transfer squared from proton to neutron in the range -0.02 to -0.15 (GeV/c)2. The spherical harmonic moments of the angular distribution are presented. Up to a mass of 1.7 GeV/c2 the moments agree with previous experiments. At higher masses Y70, Y80 and Y90 are non-zero and indicate the presence of ππ amplitudes with spin greater than 3. © 1978.

Abstract:

Data on the charge-exchange reaction π-p → (π+π-π0)n have been taken at beam momenta of 12 and 15 GeV/c, using the CERN Omega Multiparticle Spectrometer. A partial-wave analysis has been made of the (3π)0 system. We observe both natural and unnatural spin-parity production. The natural parity states can be identified with established resonances. In addition a natural spin-parity enhancement is observed at a mass of about 2 GeV/c2 with JP = 4+ preferred. We have called this effect the A2* (2030). The unnatural spin-parity production found is consistent with reggeized Deck model predictions. No unambiguous A1 or A3 production is observed. © 1978.