The differential cross sections for γ p→ π + n from hydrogen and the π − π + ratios from deuterium were measured at nine c.m. angles between 30° and 150° for laboratory photon energies between 260 and 800 MeV. A magnetic spectrometer with three layers of scintillation hodoscope was used to detect charged π mesons. The cross section for γ n→ π − p was obtained as a product of d σ d Ω (γ p →π + n ) and the π − π + ratio. The overall features in the cross sections of the two reactions, γ p→ π + n and γ n→ π − p, and in the ratios, π − π + , agree with predictions by Moorhouse, Oberlack and Rosenfeld, and Metcalf and Walker. An investigation of the possible existence of an isotensor current was made and a negative result was found. In detailed balance comparison with the new results on the inverse reaction π − p→ γ n, no apparent violation of time-reversal invariance was observed.
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The differential cross sections of p p elastic scattering at 0.7 GeV/ c were obtained in the range 0.0018<| t |⩽0.0320 GeV 2 . From the interference between the Coulomb and the nuclear amplitude, the ratio of real to imaginary part of the forward nuclear amplitude was found to be +0.33±0.04.
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FIT FOR FORWARD NUCLEAR AMPLITUDE IN COULOMB INTERFERENCE REGION.
Based on a sample of about 3500 events, we have measured the total and differential cross sections of p p → n n in the 700–760 MeV/ c incident momentum region. It is found that σ CE = 10.7 ± 0.2 mb at the average momentum of 730 MeV/ c . The differential angular distribution is characterised by a sharp peak and a dip in the forward direction followed by a secondary maximum. The position of the dip corresponds to | t | ≈ m π 2 . These results are compared with the predictions of the model of Bryan-Phillips. On the other hand, this dip-bump structure can be well understood on a simple picture involving a π exchange and a constant background (for | t | ≲ 3 m π 2 ).
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We have investigated ω production in the reaction π−p→ωn very close to threshold. The dependence of the mass, width, branching ratio, and cross section upon the final-state c.m. momentum, P*, were studied. The mass and width were independent of P* with values of 782.4 ± 0.5 and 10.22 ± 0.43 MeV, respectively. The branching ratio Γ(ω→π0γ)Γ(ω→π+π−π0) was also constant, having a value of 0.084 ± 0.013. An upper limit of 0.18 was set on the branching ratio Γ(ω→π0π0γ)Γ(ω→π0γ). We observed a rapid fall in the cross section below P*=100 MeV/c. This could not be explained in terms of S-wave production alone, but could be fitted by a resonant P wave plus a noninterfering S wave.
CROSS SECTION DEPENDENCE ON FINAL STATE CENTRE OF MASS MOMENTUM. TABULATED VALUES TAKEN FROM TABLE 1 OF H. KARAMI ET AL., NP B154, 503 (1979).
Data are presented from a high statistics bubble chamber experiment to study K − p interactions in the c.m. energy range 1775 to 1957 MeV. For the reactions K − p → K − p, K − p → K 0 n , K − p → Λπ 0 and K − p → Σ ± π ∓ channel cross sections, differential cross sections and, where appropriate, polarisation distributions have been obtained. The channel cross sections for K − p → Σ 0 π 0 are presented. In general the results are in agreement with those previously published although a significant discrepancy has been found in the Σ ± π ∓ cross sections at the lower energies. New measurements of the Σ ± lifetimes have also been obtained ( τ Σ − = 1.49 ± 0.03 × 10 −10 sec, τ Σ + = 0.807 ± 0.013 × 10 −10 sec).
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THE FORWARD DIFFERENTIAL CROSS SECTION IS THE EXTRAPOLATED VALUE OF THE LEGENDRE POLYNOMIAL FIT.
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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.
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The K L o p → K S o p differential and total cross-section and the forward scattering amplitude phase φ have been measured in the 1.5 to 2.3 GeV centre of mass energy range. The data is compared with predictions based on recent K ± N phase shift solutions. Best agreement is found for K + N solutions which do not warrant an I=0 P 1 2 exotic Z ∗ o (1800) baryon.
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A search for narrow resonances in the reaction e + e − → hadrons in the mass regions 1915–2345 MeV and 2970–3090 MeV has been perforned at ADONE, the Frascati storage ring. With 90% confidence level our data exclude the production of narrow resonances with integrated cross section larger than 20% of the integrated cross section for production of the J/Ψ (3100 MeV).
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The total and differential cross sections of the K¯0p→Λπ+ and K¯0p→∑0π+ reactions have been measured in the centre-of-mass energy range of l.5 to 2.3 GeV. Using our K¯0p→∑0π+ data as well as available cross-section data of isospin related channels, we have calculated the total I=0K¯N→∑π cross section as function of energy. The results are compared with predictions obtained from K¯N phase-shift analyses.
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Measurements are reported of the differential cross section for the reaction π−p→π−p,π0n,andηn at three angles close to 180° and for incident momenta in the range 0.6 to 1.0 GeV/c. The three measurements were made simultaneously at 1% intervals of beam momentum. The data on elastic scattering resolve a discrepancy between two earlier experiments. They also show clearly the effect of the opening of the ηn channel. The charge-exchange data show that I-spin bounds are not violated in the kinematic region covered. The ηn data can be adequately described with known s-channel resonances. No evidence for narrow N*'s is seen in any channel.
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