The differential cross section has been measured for the reaction γ+p→K+ + Λ atk=1.3 GeV andCM angles between 6 ° and 90 ° and for the reaction γ+p→K+ + ∑0 atk=1.45 GeV andCM angles between 10 ° and 85 °. In addition 10 differential cross sections of the two reactions in the energy region betweenk=1.327 and 1.416 GeV and angles between θcm=11.2 ° and 62 ° have been obtained. The results are compared with Regge-cut-model fits by Meyer zu Hörste and Pfeil1 taking into account all availableK+ photoproduction data.
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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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The reactions γA→π±A* have been studied at four-momentum transfers −t<~0.5 GeV2 for seven elements ranging from hydrogen to lead. Exclusion-principle suppression is clearly visible at small-momentum transfer. Neither the A dependence nor the energy dependence of the cross sections agrees with the predictions of the vector-dominance model. The ratio of π−π+ production requires equal spatial distributions for the protons and neutrons in nuclei. Some K+ data are also presented.
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The interference between K L → π + π - and K S → π + π - behind a copper regenerator has been observed in a high statistics experiment. The modulus and the argument of the complex ratio ϱ ( p )/ η +- , where ϱ ( p ) is the regeneration amplitude and η +- = A ( K L → π + π - )/ A (K S → π + π - ) has been measured over the momentum interval from 2.0 GeV/ c to 6.0 GeV/ c . The phase of η +- as deduced from this measurement and from the optical model value of arg [ ϱ ( p )] is 49.3° ± 6.8°. The K L K S mass difference has been found to be Δm/ h ̵ = (0.555 ± 0.020) × 10 10 sec −1 .
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Cross sections for the reactions γp→K+Λ and γp→K+Σ0 have been measured at squared four-momentum transfer (−t) from 0.005 to 2 GeV2, at photon energies 5, 8, 11, and 16 GeV. For −t>0.2 GeV2 each of the K+ cross sections is about ⅓ of the π+n photoproduction cross section, having nearly the same energy and momentum-transfer dependence. The K+ cross sections fall off at small |t|, however, in contrast to the sharp forward spike seen in π+n; this leads to a disagreement with an SU(3) prediction for −t<0.1 GeV2. The ratio of K+Σ0 to K+Λ cross sections is typically between 0.5 and 1.0.
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This article reports the results of a spark-chamber measurement of the reactions K−+p→K¯0+neutrals and K−+p→Λ0+neutrals with an incident kaon momentum of 7.7 GeV/c. The production cross sections for these reactions are measured to be 800±50 μb and 188±18 μb, respectively. The cross-section distributions d2σdPIIdP⊥ in the center-of-mass system with large momentum transfer are discussed in terms of a fireball model of production.
Axis error includes +- 0.0/0.0 contribution (?////NEUTRAL DECAY MODES, ETC).
The angular distributions of K + p and π + p backward elastic scattering have been measured at 5.2 and 6.9 GeV/ c . Backward π - p and K - p elastic scattering were studied at 6.9 GeV/ c . Backward peaks are observed in K + p scattering with an energy dependence of the form s −4 .
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Over 100 unambiguous π − + p → Λ + Λ + n events have been observed in a magnet spark chamber. The data provide good evidence for peripheral production of Λ Λ and n Λ (via meson exchange) and against peripheral n Λ (double baryon exchange). No resonances in the Λ Λ system are observed. Angular distributions and Λ( Λ ) polarizations are analysed.
Axis error includes +- 0.0/0.0 contribution (?////Corrected for neutral decays, absorption).
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Only statistical errors are given.
Only statistical errors are given.
The transmission regeneration amplitude after a thick copper block has been measured. The quantity {∣ƒ(0)- overlineƒ(0)∣ }/{k} varies from 20.0 $\pm$ 1.4 mb at 2.75 GeV/c to 13.6 $\pm$ 1.2 mb at 7.25 GeV/c. Results are in agreement with optical model calculations in which real and imaginary parts of the amplitudes for single nucleon scattering are determined from forward dispersion relations and total cross-sections.
Regeneration amplitude.
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