-r+-r on accelerators it is practically impossible to identify the 1("0_ mesons from one decay y-quantum at angles e1(" ~ 40°, Hence, at angles e1f "'" 0° we detected the two decay photons.

In the most unfavorable case of an angle of 44 in the 10w-eneJ;gy region, this background did not exceed 2-30/0 in any series. The background from the empty target varied from 300/0 (relative to count from deuterium) in the first channel Clow energies) to 150/0 in the last. This resulted in relatively large statistical errors (Fig. 13), which varied from 1 to 50/0 for angles of 44 and 124 andfrom 2 to 70/0 for 84 0 0 0 • The width of the time analyzer channels was pel:iodically adjusted. The maximum drift of the width of any one channel did not exceed 50/0.

Energy dependence of ratio of differential yields ofdecay y-quantafrom 1I"°-mesons formed in processes y + d - d(pn) + 11"0 and y + P _ P + 11"0. The solid line represents the results of calculations based on phenomenological theory. Figures 23 and 24 show that for angles e1l" > 90° the cross section decreases more rapidly with increase in angle than the calculations predict. '" For instance, for e y = 124° the calculated cros~ sections are approximately twice the experimentaiones. As the figure shows, this discrepancy depends strongly on the angle and weakly on the energy and, hence, cannot be due to multiple scattering effects.

### Photomesic and Photonuclear Processes: Proceedings (Trudy) of the P. N. Lebedev Physics Institute by A. I. Lebedev, E. I. Tamm (auth.), Academican D. V. Skobel’tsyn (eds.)

by Anthony

4.3