F. Sergiampietri

Reaction π− p → η′n in the 15–40 GeV/c momentum range☆

Abstract Measurements were made of the cross section of the reactions π−p → ν′(958)n, η′ → 2γ at momenta at 15, 20, 25, 30 and 40 GeV/c. The experiment was carried out on the IHEP 70 GeV accelerator using the 648 channel hodoscope spectrometer NICE for γ-ray detection. A total of 6000 η′ mesons were recorded. A sharp drop is seen in the differential cross section for t → 0. The dependences of the differential cross sections for the π−p → η′n and π−p → η n on t are identical. On the basis of the ratio of the cross sections for these reactions at t = 0, i.e. R( η′ n ) t=0 = 0.55 ± 0.06 , the singlet-octet mixing angle for pseudoscalar mesons was determined to be β = −(18.2 ± 1.4)°.

X0 → 2γ from π− p → neutral meson + neuron at 3.8 GeV/c

Abstract We report on a measurement for the branching-ratio X 0 → 2γ X 0 ar all. Our result is X 0 → 2γ X 0 → all = (2.9 ± 0.9)% .

Results on ππ-interaction in the reaction π−p → πoπon at 8 GeV/c

Abstract We compare published ππ-phase shifts with results from an analysis of the reaction π − p → π o π o n. The ‘up’-solution as well as the ‘in-between’ -solution for the I = 0 s-wave ππ-scattering are ruled out. The only set of s-wave phase shifts consistent with our data is the ‘up-down’-solution with a rapid rise of σ 0 0 near the KK-threshold.

Results on the production cross sections π− p → neutrals and π− p→ χ↳2γ0 n at 3.8, 6, 8 and 12 GeV/c☆

The ratio between the cross sections for the reactions π− p→ χ↳2γ0 n and π−p → η→2γ n has been measured to be (2.4 ± 0.9) × 10−2, (2.1 ± 0.6) × 10−2 and (2.8 ± 1.3) × 10−2 at 3.8,6,8 and 12 GeV/c incident momentum respectively. At the same momenta the cross section for πt- p → neutrals is (1.48 ± 0.09) mb, (0.86 ± 0.05) mb, (0.64 ± 0.04) mb and (0.42±0.03) mb.

Study of the reaction at 3, 8, 6 and 8 GeV/c

Abstract Results are given for the production differential cross sections and the ω decay angular distribution in terms of the ω spin density matrix elements.

Search for the decay mode ω→ηγ in the reaction π−p → n + neutral boson

Abstract We have searched for decays in a sample of 1252 π − p →3 γ +n events with the 3γ invariant mass in the ω-region. Practically all events fit and we find .

Measurement of π−p → π0π0n at 6, 8 and 12 GeV/c☆

Abstract All γs and the neutron from the reaction π − p → π 0 π 0 n are detected. The magnitude of the π 0 π 0 S-wave and the cosine of its phase angle (relative to the known D-wave) are determined. The I = 0 amplitude, S 0 , is near the unitarity limit in the range 600 to 900 MeV and again around 1200 MeV.

Study of the Reaction K- p --> anti-K0 n at Momenta of 25-GeV/c and 40-GeV/c

ALPHA EFFECTIVE FOUND TO BE (0.39 +- 0.02) + (0.84 +- 0.07)*T. THIS PAPER IS THE SAME AS W. D. APEL ET AL., NP B129, 275 (1977).