Cross-sections for the photo-production of ?0-mesons from hydrogen from 238 to 922 MeV

Abstract

Abstract. The results of a comprehensive series of measurements of the cross-sections for the photo-production of n~ from hydrogen at pion c.m. angles from 47 to 145 degrees are presented. The minimum and maximum photon energies have been 238 and 922 MeV respectively.

Cross-sections for deuteron photo-disintegration from 74 to 241 MeV

“…It is obvious that the new measurements confirm the reproducibility of our earlier data, while still showing the same systematic deviations from Bonn data we have noted elsewhere [10]. The changes made in the experimental set-up prior to the present runs are large, being almost equivalent to a complete new experiment.…”

“…After study of various alternatives, it was decided that the lowest value of proton energyresolution which could realistically be used was 5 MeV. At forward angles, this results in photon energy-resolutions which are not much larger and hence are about a factor-of-four smaller than the (1974)(1975) [10], '7 Lund (1972'7 Lund ( -1973 [9], x Bonn [11] typical value of 20 MeV used in our earlier work. This value of energy-resolution fixed the diameter of the deuterium target-cell at 25 mm and demanded a reduction of the photon beam-diameter to about 15 mm.…”

N→ΔTransition from Simultaneous Measurements ofp(γ→

“…Recent Mainz cross sections for p͑ g, p 0 ͒ (open circles) [8], and older Bonn data [14], are both noticeably lower than our results and those of [18] near the D peak.…”

New evaluation of the Baldin sum rule

“…However, pion production experiments between 1970 and 1980 display an unusual dichotomy near the peak of ∆-resonance. For photon energies either below 280 MeV or above 360 MeV, π + and π 0 data taken at Bonn [7], Tokyo [8] and Lund [9] are quite in good agreement. Instead, within this energy range the Tokyo π + data and the Lund π 0 data are consistently higher than their Bonn counterparts.…”