Emission probability of bremsstrahlung in the a decay of 210 Po was measured in a-g coincidence measurements with Si and Ge detectors. It was found that the bremsstrahlung yields are much smaller than those predicted by a Coulomb acceleration model, in which g rays are emitted during acceleration outside the barrier. This suggests that the radiation amplitude in the barrier cannot be neglected, and the discussion based on a quasiclassical approach is given. [S0031-9007(97)03609-0] PACS numbers: 23.60. + e, 23.20. -g, 27.80. + w, 27.90. + b

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In coincidence measurements with Si and Ge detectors, bremsstrahlung photons associated with the -decay of and were measured. Emission probabilities of the bremsstrahlung deduced for were for keV, and upper limits of the same order of magnitude were obtained for . They are much smaller than those predicted by a Coulomb acceleration model and are compared with a quasi-classical calculation in which the bremsstrahlung emission in tunnelling motion of particles is taken into account. It is shown that the data can be interpreted as a consequence of destructive interference of radiative amplitudes outside the Coulomb barrier with those in tunnelling.

Differential and total cross sections of the D(γ, η)pn reaction have been measured for photon energies between 600 and 1150 MeV. The data provide the information of the γn → ηn reaction above E γ ≥ 800 MeV. The total cross section shows a narrow resonance structure peaked at E γ = 1020 MeV. The angular distribution coefficients together with the total cross section are compared with the calculation of the isobar model by using the impulse approximation. Although the spin and parity of the resonance cannot be determined unambiguously, a negative parity assignment gives better fit to the data. * )

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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.