Inclusive ϱ 0 production in γ p → ϱ 0 + anything is studied at 2.8, 4.7, and 9.3 GeV, using the SLAC linearly polarized backscattered laser photon beam and the 82 inch hydrogen bubble chamber. Over this energy range the inclusive inelastic ϱ 0 cross section rises from 6.0 μb to 20.5 μb. The multiplicity, i.e. the average number of μ 0 mesons per inelastic hadronic event, has an energy dependence consistent with 1n s .
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Total (π+, p) and (p, p) cross sections in the momentum range 1.4 to 4.0 Bev/c are presented. These measurements, with an accuracy of approximately 2%, were made at the Berkeley Bevatron by using counter techniques. Pions were distinguished from protons by means of a gas-filled Čerenkov counter. The (π+, p) total cross section was found to be almost constant above 2.0 Bev/c at a value near 29 mb. The (p, p) cross section decreases gradually from 47.5 mb to 41.7 mb over the momentum range covered. Transmission measurements of π+-nucleus and p-nucleus cross sections in both good and poor geometry were made at 3.0 Bev/c. The results are compared with the predictions of the optical model. In contrast to most previous work at high energies, an essentially exact solution of the wave equation for a potential well with a diffuse edge was used. The values of the imaginary part of the optical potential that best fit the experimental data are in good agreement with the predicted values. No strong conclusion regarding the real part of the potential was possible. Absorption and total elastic scattering cross sections for Be, C, Al, and Cu are presented. The total elastic scattering cross sections from this experiment disagree with Wikner's for π−-nucleus scattering.
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Using the internal beam of DESY elastic electron-proton cross-sections were measured at various angles between 32° and 130°, and with momentum transfers ofq 2=39, 60, 80 and 110 fm−2. Two single-quadrupole spectrometers, movable around a common liquid-hydrogen target, were used for analysing the momentum of the scattered electrons. Čerenkov and shower counters discriminated against pion and low-energy background. As a cross-section reference, recoil protons from elastic scattering atq 2=10 fm−2 were used, with a quantameter serving as an intermediate monitor. The data are consistent with the Rosenbluth formula, giving real form factorsG E andG M . Both continue to decrease with increasing momentum transfer, but somewhat faster than indicated by measurements performed so far.
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Measurements of the polarised beam asymmetry parameter Σ for eta photoproduction from protons, have been carried out at incident energies of 2.5 GeV and 3.0 GeV, and for various t -values between −0.2 (GeV/c) 2 and −1.2 (GeV/c) 2 . The values of Σ are close to +1 for values of | t | less than 0.7 (GeV/c) 2 , showing that there can be little contribution from unnatural parity exchange in any Regge exchange model of the process, in disagreement with present theories. Differential cross sections for the process werre also measured, and are consistent with those from other experiments.
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In a study of photoproduction at photon energies up to 5.3 GeV in a deuterium bubble chamber the reactions γ n→p π + π − π − and γ n→p π + π − π − π 0 were analyzed. In these reactions production of the resonances Δ ++ , Δ 0 , ϱ 0 , ω and A 2 − was observed. Photoproduction of strange particles was investigated and cross sections for the reactions γ n→ Λ K + π − , Σ − K 0 π + , pK − K 0 , Λ K 0 π + π − and Λ K + π − π 0 are presented. Production of Σ − (1385) and K ∗0 (890) was observed.
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The differential cross sections of the elastic p p reaction have been measured at 1.2, 1.4, 1.8 and 2.6 GeV/ c incident p momentum. The measurements have been performed at the CERN PS using a system of multiwire proportional chambers. The angular region covers scattering angles from 0 to ∼200 mrad. Interference effects between the Coulomb and the nuclear amplitudes are used to derive the ratio of the real to imaginary part of the forward nuclear amplitude. These ratios are compared with theoretical predictions.
'MS'. 'TBIN'.
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The Λ-proton elastic scattering cross section has been measured between 1 and 17 GeV/c in a bubble chamber experiment. These are the first measurements of the elastic cross section for pΛ>5 GeV/c. The Λ's were produced by 25-GeV/c proton interactions in a platinum target. The cross section falls from 22 to 4 mb over the region. No significant polarization is observed.
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CORRECTION MADE FOR KL P --> KS P.
Qausi-elastic ω production by ep scattering in the kinematic region 0.3. < Q 2 < 1.4 GeV 2 and 1.7 < W < 2.8 GeV was studied using a streamer chamber at DESY. The production angular distribution for γ V p → ω p has a strong non-peripheral component for W < 2 GeV. The ω production cross section falls by a factor of 4 as W changes from 1.7 to 2.8 GeV. In contrast the cross section for ω production with | t | < 0.5 GeV 2 is W independent between 1.7 and 2.8 GeV and for W > 2.0 GeV consistent in both W and Q 2 dependence with the predictions of a model based on one-pion exchange and diffraction.
FOR ALL T-VALUES. THE GAMMA* P TOTAL CROSS SECTION WAS TAKEN FROM A FIT TO THE DATA OF S. STEIN ET AL., PR D12, 1884 (1975). 'PPD'.
'PPD'. PERIPHERAL OMEGA PRODUCTION.
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The backward angular distributions obtained in an experiment at the Zero Gradient Synchrotron of Argonne National Laboratory were used to systematically study the energy dependence of the 180° differential cross section for π+p elastic scattering in the center-of-mass energy region from 2159 to 3487 MeV. At each of 38 incident pion momenta between 2.0 and 6.0 GeV/c, a focusing spectrometer and scintillation counter hodoscopes were used to obtain differential cross sections for typically five pion scattering angles from 141° to 173° in the laboratory. Values for dσdΩ at 180° were then obtained by extrapolation. A resonance model and an interference model were used to perform fits to the energy dependence of dσdΩ (180°). Both models led to good fits to our data and yielded values for the masses, widths, parities, and the product of spin and elasticity for the Δ(2200), Δ(2420), Δ(2850), and Δ(3230) resonances. Our data confirm the existence of the Δ(3230) and require the negative-parity Δ(2200).
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