Coherent effects in synchrotron radiation (SR) have been observed for the first time from 180-MeV short electron bunches of 2.5 mm using the Tohoku 300-MeV Linac. The intensity of the coherent SR was about 10 5 times as strong as that of incoherent SR in the wavelengths of 0.4-2.2 mm. This enhancement factor corresponds to the number of electrons in a bunch. The SR intensity showed a quadratic dependence on the electron beam current. The radiation was mainly polarized in the orbital plane. The possibility of induced rf in a vacuum chamber was excluded experimentally.

The photoproduction process of neutral kaons on a liquid deuterium target is investigated near the threshold region, Eγ = 0.8-1.1 GeV. K 0 events are reconstructed from positive and negative pions, and differential cross sections are derived. Experimental momentum spectra are compared with those calculated in the spectator model using a realistic deuteron wave function. Elementary amplitudes as given by recent isobar models and a simple phenomenological model are used to study the effect of the new data on the angular behavior of the elementary cross section. The data favor a backward-peaked angular distribution of the elementary n(γ, K 0 )Λ process, which provides additional constraints on current models of kaon photoproduction. The present study demonstrates that the n(γ, K 0 )Λ reaction can provide key information on the mechanism of the photoproduction of strangeness.

In the above-named study of the neutral kaon photoproduction, the cross sections given in Figs. 10 and 11 were wrong due to trivial mistakes, mainly in estimating the number of beam photons. The normalization factors for the cross sections are found to be larger by a factor of approximately 3.9 compared to the previous one, though it depends on the K 0 momentum. The corrected spectra are shown in Fig. 11 (numberings are the same as the original ones). As a result, the r K 1 Kγ value obtained by fitting the K 0 spectra in the lower photon energy region (0.9 E γ < 1.0 GeV) should be replaced by the new value of r K 1 Kγ = −1.405 for the Saclay-Lyon A (SLA) model. The phenomenological parameters are also changed: a 0 = 0.3532, a 1 = −0.2152, a 2 = −0.0359, and e 0 = −0.0866 with χ 2 /n.d.f. = 0.80.By these corrections, the experimental cross sections are larger than those calculated by the Kaon-MAID model in the momentum region of P K 0 < 0.4 GeV/c both in the lower and higher photon beam energies. However, the K 0 spectral shapes in the laboratory system are essentially the same as those of the previous ones and the discussion does not change. In Fig. 12, the K 0 angular distributions for the SLA and PH models calculated with the new parameters are shown together with those for the Kaon-MAID model. It suggests a much enhanced backward K 0 distribution in the c.m. system because the SLA and PH1 models are preferred to reproduce the new results with larger cross sections.

No abstract

No abstract