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Only statistical errors are given.
Only statistical errors are given.
Measurements on large-angle photoproduction of π+ mesons from hydrogen have been made at the Stanford Linear Accelerator Center for photon energies between 5 and 15.5 GeV and u values from +0.05 to -1.8 (GeV/c)2. The measured cross section decreased with energy approximately as k−3, showing no shrinkage in this range of u values. Furthermore, it had a smooth u dependence with no sign of a dip at u≃−0.15 (GeV/c)2 as would be expected from nucleon exchange. π−Δ++ production was measured at 5 GeV and shows a rapid decrease with increasing |u|.
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Electron-proton elastic scattering cross sections have been measured at the Stanford Linear Accelerator Center at four-momentum transfers squared (q 2 ) of 1.0, 1.5, 2.0, 2.5and 3.75 (GeV/ c ) 2 . The angular distributions at q 2 = 2.5 and 3.75 (GeV/ c ) 2 are sufficient to provide values of the ratio G E / G M independent of the results from other laboratories. Our results are compatible with scaling, G E (q 2 ) = G M (q 2 )/ μ , within the experimental errors.
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The charge excharge reaction K − p → K 0 n has been studied in a event/μb exposure of the CERN 2m hydrogen bubble chamber to a 3.95 GeV/ c K − beam. The differential cross section d σ /d t exhibits a change of slope at −1 ≈ 0.8 GeV 2 .
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Measurements have been made on Compton scattering for photon energies between 5 and 17 GeV and t values from -0.06 to -1.1 (GeVc)2. The data were obtained by performing a coincidence between the Stanford Linear Accelerator Center 1.6-GeVc spectrometer and a Lucite shower counter. The scattering appears diffractive out to high t values, but the cross sections seem not to be in good agreement with the prediction of a strict vector-meson-dominance model.
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We present an analysis of the K ππ system produced in 10 GeV/ c K + p interactions. We show that the low-mass enchancement between 1.2 and 1.4 GeV/ c 2 on the K ππ mass spectrum is predominantly 1 + throughout, give the relative amplitudes for the decay of this system into K ∗ (890) π and K ρ , and offer new evidence for the presence of two 1 + resonances in this mass region.
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DIFFERENTIAL CROSS SECTION FOR THREE MASS BANDS IN Q-REGION. NORMALIZATION UNCERTAIN - NO UNITS FOR D(SIG)/DT GIVEN ON FIGURE. NUMERICAL VALUES TAKEN FROM THE COMPILATION LST7V2 FOX 72B. ERRORS ADDED AS 1/SQRT(EVENTS).
We present the results of a study of 1173 uniquely identified events of the K 0 π + p final state produced in 10 GeV/ c K + p interactions. This final state is dominated by the quasi two-body processes K + p → K 0 N ∗+ (890 p and K + p → K ∗+ (1420) p . The background is very low and there is little overlapping of resonance bands. We present cross sections, t -distributions and decay angular distributions for the contributing reaction channels. Dips are observed near t = 0 in the differential cross sections for all three processes.
BREIT-WIGNER FIT.
NUMERICAL VALUES TAKEN FROM THE COMPILATION LST7V2 FOX 72B.
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We have completed measurements of the differential cross section for γ+p→π0+p, and the asymmetry with polarized photons, for incident photon energies from 4 to 18 GeV and momentum transfers between t=−0.1 and −1.4 (GeV/c)2. The experiment was performed at the Stanford Linear Accelerator Center, using the SLAC 1.6-GeV/c spectrometer to analyze protons recoiling from a hydrogen target. For the cross-section measurements a normal collimated bremsstrahlung beam was used. For the asymmetry measurements the polarized photons were produced by coherent bremsstrahlung from a diamond crystal, and a coincidence was required between the recoil proton and one of the π0 decay photons in a shower counter.
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Differential cross sections have been measured for nucleon-isobar production and elastic scattering in p−p interactions from 6.2 to 29.7 GeVc in the laboratory angle range 8<θsc<265 mrad. N*' s at 1236, 1410, 1500, 1690, and 2190 MeV were observed. Computer fits to the mass spectra under varying assumptions of resonance and background shapes show that conclusions on t and s dependence are only slightly affected despite typical variations in absolute normalization of ± 35%. Logarithmic t slopes in the small- |t| range are ∼15 (GeVc)−2 for the N*(1410), ∼5 (GeVc)−2 for the N*'s at 1500, 1690, and 2190 MeV, and ∼9 (GeVc)−2 for elastic scattering. Also for the small- |t| data, cross sections for N*'s at 1410, 1500, 1690, and 2190 MeV and for elastic scattering vary only slightly with Pinc consistent with the dominance of Pomeranchuk exchange and with diffraction dissociation. A fit of N*(1690) total cross sections to the form σ∝P−n gives n=0.34±0.06, while for elastic scattering n=0.20±0.05. For the N*(1690) the effective Regge trajectory has the slope αeff′(0)=0.38±0.17. When compared with N* production in π−, K−, and p¯ beams these data also agree with approximate factorization of the Pomeranchuk trajectory. N*(1236) cross sections are consistent with other measurements at similar momenta. For −t>1 (GeVc)−2, elastic scattering cross sections decrease approximately as Pinc−2, and they and N*(1500)− and N*(1690)− production cross sections have t slopes consistent with 1.6 (GeVc)−2.
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Electron-proton elastic-scattering cross sections have been measured at the Stanford Linear Accelerator Center for four-momentum transfers squared q 2 from 1.0 to 25.0 (GeVc)2. The electric (GEp) and magnetic (GMp) form factors of the proton were not separated, since angular distributions were not measured at each q 2. However, values for GMp were derived assuming various relations between GEp and GMp. Several theoretical models for the behavior of the proton magnetic form factor at high values of q 2 are compared with the data.
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