M.A. Pouchon

Test of C invariance in the three pion decay of the η meson

Abstract The study of the decay distribution of a sample of 10 665 η→π + π - π 0 observed in a magnet spark chamber experiment shows no evidence for charge conjugation violation. The result for the right to left asymmetry in the Dalitz plot is 0.3% with a statistical error of ±1%.

Dalitz plot analysis of the decay η → π+π−π0

Abstract The Dalitz plot of 7170 decays η→π+π−π0 has been fitted with several matrix elements. The slope of a purely real linear matrix element ME = 1 + α[( 3T 0 Q ) − 1] is α = −0.55 ± 0.02. Upper limits for possible contributions of ΔI=0 and ΔI=2C-violating amplitudes are given.

Performance of a large magnet spark chamber

Abstract The description of a 60 × 67 × 160 cm3 spark chamber in a 10.5 kG magnetic field and a report on its performance are given. This instrument was used at the CERN Proton Synchrotron for the detection of the neutral (and non-π0) reaction products of π−, K− and p on hydrogen. The sources of the systematic deviations in spark position have been investigated and corrections have been devised to compensate for them. The residual random errors are: 1. 1. the rms deviation of individual sparks from the fitted trajectory σy = 0.18 mm in space. 2. 2. the rms measurement error σy meas = 0.09 mm in space. The MDM of the instrument is 1000 GeV/c and the rms error in the mass of K10 mesons of 7 GeV/c momentum is Δm = 7.3 MeV/c2.

X° production in π − p interactions

Abstract A study of the reaction π−p → Xno near threshold for two incident pion momenta has yielded the following values of the cross-section: (22 ± 4) μb at 1.50 GeV/c and (33 ± 6) μb at 1.52 GeV/c. These cross-sections refer to the decay mode X° → π+π−η (η→ [rmneutrals).

Dalitz plot analysis for the decay η → π+π−γ

Abstract A purified sample of 1088 η → π+π−γ decays is corrected for detection efficiency effects. The | cos θ | distribution indicates that the two pions are mainly in a J = 1 state. The γ energy dependence of the matrix element is incompatible with the simplest gauge invariant form but is well fitted by a ϱ-dominance type model.

Charge conjugation in η → π+π−γ☆

Abstract A sample of 1620 η → π+π−γ observed in a magnet spark chamber experiment shows no evidence for charge conjugation violation. The result for the asymmetry is A = +1.5% with a statistical error of ±2.5%.

Dalitz plot analysis for the X0 decaying into ηπ+π−☆

Abstract The Dalitz plot for the decay X 0 → π + π − η has been analysed and shows a dependence on ππ mass. Various quantum numbers assignments are discussed.