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. * )

No abstract

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.

The total cross sections were measured for coherent double neutral-pion photoproduction on the deuteron at incident energies below 0.9 GeV for the first time. No clear resonancelike behavior is observed in the excitation function for W γd = 2.38-2.61 GeV, where the d * (2380) dibaryon resonance observed at COSY is expected to appear. The measured excitation function is consistent with the existing theoretical calculation for this reaction. The upper limit of the total cross section is found to be 0.034 µb for the dibaryon resonance at W γd = 2.37 GeV (90% confidence level) in the γd → π 0 π 0 d reaction.