Single photoproduction of neutral π-mesons on hydrogen in the extreme forward direction at 4 and 5.8 GeV

doi:10.1016/0550-3213(70)90202-6

Nuclear Physics B

Volume 20, Issue 1, 15 June 1970, Pages 191-200

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Abstract

The differential cross section of the reaction γp→pπ^o has been measured at the Deutsches Elektronen Synchroton (DESY) Hamburg, at mean photon energies of 4.0 and 5.8 GeV for pion c.m. angles between 0^o and 5^o in steps of 1^o. The production near 0^o is dominated by the Primakoff effect.

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Cited by (37)

Regge poles and cuts in π<sup>0</sup> photoproduction and related reactions
1978, Nuclear Physics, Section B
A previous analysis of intermediate- and high-energy photoproduction data using finite-energy sum rules and fixed-t dispersion relations is extented to enable effects due to Regge poles and cuts to be distinguished. This is achieved by requiring Regge poles to be evasive and to have nonsense wrong signature zeros, whereas cuts are parametrised by effective two-pole forms and are taken to be self-conspiring with minimal structure in their residues. These constraints, together with phase information provided by data on the Primakoff effect, enable an essentially unique separation of pole and cut effects to be made. We compare our results with popular cut models of hadronic reactions relevant at accelerator energies, and with the universal impact parameter hypothesis. None of these are able to reproduce all the features we find in our amplitudes. Finally, we show how our results can cast light on the puzzling absence of dips in η⁰ photoproduction and π⁰ electroproduction, by making plausible assumptions about the isospin and q² dependences of our amplitudes, respectively.
Small-angle compton scattering on hydrogen and deuterium
1977, Nuclear Physics, Section B
We have measured elastic scattering of 5 and 6 GeV photons on hydrogen and deuterium in the angular range 10–50 mrad. On hydrogen we observe a forward diffraction peak with a slope of 8.5 (GeV/c)⁻². The extrapolated forward cross sections in units μb/(GeV/c)² are 0.82 ± 0.04 at 5 GeV and 0.79 ± 0.04 at 6 GeV. They are consistent with the calculated amplitudes obtained from total cross section measurements via the optical theorem and dispersion relations assuming negligible contributions of spin-dependent amplitudes. Deuterium cross sections show a transition from coherent scattering at low |t| to incoherent scattering at higher |t|. They indicate that the isovector exchange amplitude a₁ is very small compared to the isoscalar a₀. We obtain , , , .
Small-angle photon scattering on complex nuclei
1977, Nuclear Physics, Section B
Photons of 3 GeV and 5 GeV were scattered on 7 different elements, ranging from Be to Au, and detected with a pair spectrometer. The angular distributions show diffractive patterns consistent with known nuclear sizes. Forward cross sections are 20–30% lower than expected from an A² dependence. This shadowing effect is qualitatively explained by photon interactions via intermediate hadronic states.
Photon-nucleus collisions and the relative phase between the γ+p→π0+p and ϱ0+p→π0+p amplitudes
1976, Nuclear Physics, Section B
The photoproduction of neutral pions with nuclear targets at photon energies in which experimental data are available (E_γlab) ≤ 8.7 GeV, 0.1 ≤ −t ≤ 0.25 (GeV/c)² is analyzed within the framework of Glauber theory. In our approach the quantity A_{eff=σ(γA→π⁰A)/gs(γN→π⁰N)} depends essentially on the ration depends essentially on the ratio A_ϱ0N→π⁰N/A_γN→π⁰N≡^|A_ϱ0N→π⁰N/^AγN→π⁰N|e^i∅ As the moduli of these amplitudes are known experimentally, from the nuclear data one may extract the value of ∅. It is found a value ∅ ≈ −(20° to 35°) at variance with VMD predictions (∅=0).
Forward photoproduction of neutral pions from protons in the resonance region
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Exchange-component analysis of neutral pseudoscalar meson photoproduction
1975, Nuclear Physics, Section B
π⁰ and η photoproduction data in the region of 4 GeV are decomposed into t-channel exchange components of definite isospin and parity. The latter are discussed in terms of Regge exchange models and compared to vector-meson dominance related processes. The isospin-one natural parity-exchange component is smooth and structureless. The dominant unatural parity exchange in π⁰ photoproduction has isospin zero. As in π^± photoproduction the ratio of natural to unnatural parity exchange is found to be larger than the vector-dominance expectation. Complementary information from a recent spin decomposition of γp → π⁰p gives further insight into the SU (3) properties of the exchanges. We predict unmeasured quantities and stress, in particular, the importance of studying γn → π⁰n with polarised photons.

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Single photoproduction of neutral π-mesons on hydrogen in the extreme forward direction at 4 and 5.8 GeV

Abstract

Phys. Letters

Nucl. Phys.

Phys. Rev.