Results are presented on elastic scattering of 10.1 GeV/ c K − mesons on protons, based on a sample of 16 261 kinematically-fitted bubble-chamber events. The differential cross section is given over the | t |- range of 0.06 to 2.5 GeV 2 and is fitted with the expressions a e bt , A e Bt + Ct 2 and ( P e Qt + Re St ) over various intervals of t . The results are compared with those of other experiments at nearby energies. Upper limits of | α | < 0.28 and σ B < 0.4 μ b (both at a 90% confidence level) are given for the ratio of real to imaginary part of the forward-scattering amplitude and the backward-elastic-scattering cross section, respectively.
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ERROR INCLUDES STATISTICAL ERROR AND ERROR IN TOTAL CROSS SECTION USED FOR NORMALIZATION. EXTRAPOLATION OF D(SIG)/DT TO T=0 PROVIDES ABOUT 0.5 PCT UNCERTAINTY.
NO BACKWARD EVENTS OBSERVED. LARGEST ANGLE EVENT SEEN WAS AT 64 DEG (-T = 2.33 GEV**2).
The reaction K + p → K ∗o (892) Δ ++ (1236) has been studied at 3 GeV/ c in both a hydrogen and a deuterium bubble chamber experiment. The production mechanism is described by a Regge-type model using π- and B-exchange. The joint decay distributions are analysed in various frames and compared with quark-model predictions.
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New measurements on the reactionsγp→K + Λ and γp→K + Σ o have been performed at the DESY synchrotron at c.m. angles around 90° and photon lab. energies from 1.19 to 1.68 GeV. The produced K + mesons were analyzed by a magnet spectrometer, two thresholdCˇerenkov counters and a time-of-flight measurement. The obtained differential cross-section data show a smooth energy behaviour for the K + Λ production whereas for theK + Σ o production the data trace out a bump at a c.m. energy W ≈ 1.9GeV.
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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.
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Previous measurements of the cross section asymmetry for single π + production on protons with linearly polarized photons of 3.4 GeV have been extended to momentum transfers within the forward peak, i.e. − = 0.0026, 0.006 and 0.01 (GeV/ c ) 2 . The results are in good agreement with pion exchange models.
Axis error includes +- 6/6 contribution.
Electron-proton elastic scattering cross sections have been measured at four-momentum transfers between 1.0 and 3.0 (GeV/ c ) 2 and at electron scattering angles between 10° and 20° and at about 86° in the laboratory. The proton electromagnetic form factors G E and G M were determined. The results indicate that G E ( q 2 ) decreases faster with increasing q 2 than G M ( q 2 ).
Axis error includes +- 2.5/2.5 contribution (Due to counting statisticss, separation of elastic events, beam monitoring, incident energy, scattering angle, proton absorption, solid angle, target length and density).
CONST(NAME=MU) is the magnetic moment.
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Polarization of Λ hyperons and differential cross sections for the reaction γ+p→K++Λ were measured at the K+-meson center-of-mass angles around 45°, 70°, and 90° for the incident photon energies of 1054, 1100, and 1160 MeV. The K+ mesons were detected with a magnetic spectrometer and a velocity-selection system based on the energy loss and the time of flight. The polarization of Λ was determined by measuring the up-down asymmetry of protons in the decay Λ→pπ− with respect to the production plane. The results show a dominant sinθK* dependence of the polarization at the region of the third resonance and are consistent with a contribution of the P11 resonance with a mass of about 1700 MeV.
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We present results of measurements on photoproduction of ρ mesons. Analysis of 106 measured ρ events in a four-dimensional data matrix dσ(A, m, p, t⊥)dΩdm with dimensions 14×20×10×20 yields precise information on nuclear density distributions for ρ production. We obtain for the Woods-Saxon radii R(A)=(1.12±0.02)A13 and, using the vector dominance model, σρN=26.7±2.0 mb and γρ24π=0.57±0.10.
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