We measured 30 000 wide-angle electron-positron pairs from the reaction γ+p→p+e++e− in the invariant-mass region 500≤m≤1060 MeV. The photoproduction amplitudes of the ρ, ω and ϕ mesons were measured to deviate from being pure imaginary by 37.5°−3.1°+2.8°, 29.6°−12.9°+15.5°, 3.4°−4.2°+5.3°,respectively.
DEVIATION OF VECTOR MESON PHOTOPRODUCTION PHASES FROM PURE IMAGINARY.
We have measured the reaction γ p → p π + π − in the DESY 1 m Streamer Chamber. The dominant ϱ o production is analyzed in terms of various models.
No description provided.
FOR ALL EVENTS.
FOR ALL TWO PION EVENTS.
The reaction γp→; π + π − p in the energy range 4.1 to 6.2 GeV has been studied with a tagged photon beam incident on a liquid hydrogen target in the DESY one-meter streamer chamber. The reaction is analysed in terms of the longitudinal phase space (LPS) method. The one-pion-exchange model for Δ(1236) production and decay is examined. For the diffractive part of the LPS a dual model with pomeron exchange is investigated. In particular, the s -channel helicity conservation dual model of Dewey and Humpert describes the data well.
No description provided.
CORRECTED FOR LOSSES AT SMALL T (UNLIKE VALUES OF 'REF 1'). BACKGROUND SUBTRACTION ERROR HAS BEEN ADDED QUADRATICALLY TO THE STATISTICAL ERROR.
No description provided.
We have studied photoproduction using a 1 m streamer chamber at DESY and a tagged photon beam with an energy range of 1.6 GeV < E γ < 6.3 GeV. We analysed approximately 30 000 events and report topological, channel and resonance production cross sections for a large number of reactions with three and five outgoing charged particles.
CHANNEL CROSS SECTIONS FOR 3, 5 AND 7 PRONG REACTIONS.
'PARAMETRIZATION'.
'INTERFERENCE'.
We have measured large-angle electron-positron pairs from the reaction γ +Be → Be+e + +e − in the e + e − invariant-mass region of 610 < m < 850 MeV/ c 2 . The phase of the photoproduction amplitude of the ϱ-meson at 4.1 – 6.1 GeV was found to deviate from pure imaginary by 11.8° ± 4.4° which corresponds to a ratio of the real to imaginary ϱ-nucleon amplitude of β = −0.2 ± 0.1.
No description provided.
A measurement of backward photoproduction of charged pion pairs on protons is reported. The pion pair mass spectrum shows strong ϱ ° and f production. Data are presented on the u and s dependence for ϱ O and f, together with the decay polarisation for the ϱ O .
No description provided.
No description provided.
AVERAGED OVER U RANGE OF EXPERIMENT. NO EVIDENCE FOR ANY LARGE S-WAVE CONTRIBUTION TO THE PI PI SYSTEM IN THE RHO0 MASS REGION (RHO(0S) < -0.03 +- 0.13). U CHANNEL FRAME: Z AXIS IN INCIDENT PROTON DIRECTION IN THE DIPION REST FRAME.
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