Lessons to be learned from the coherent photoproduction of pseudoscalar mesons

Abstract

We study the coherent photoproduction of pseudoscalar mesons---particularly of neutral pions---placing special emphasis on the various sources that put into question earlier nonrelativistic-impulse-approximation calculations. These include: final-state interactions, relativistic effects, off-shell ambiguities, and violations to the impulse approximation. We establish that, while distortions play an essential role in the modification of the coherent cross section, the uncertainty in our results due to the various choices of optical-potential models is relatively small (of at most 30%). By far the largest uncertainty emerges from the ambiguity in extending the many on-shell-equivalent representations of the elementary amplitude off the mass shell. Indeed, relativistic impulse-approximation calculations that include the same pionic distortions, the same nuclear-structure model, and two sets of elementary amplitudes that are identical on-shell, lead to variations in the magnitude of the coherent cross section by up to factors of five. Finally, we address qualitatively the assumption of locality implicit in most impulse-approximation treatments, and suggest that the coherent reaction probes---in addition to the nuclear density---the polarization structure of the nucleus.

Manuscript is 27 pages long and includes 11 eps figures

References in corpus (5)

• Updated analysis of $\pi$N elastic scattering data to 2.1~GeV: The Baryon Spectrum
• Updated resonance photo-decay amplitudes to 2 GeV
• Coherent Photoproduction of Pions on Spin-Zero Nuclei in a relativistic, non-local Model
• Coherent eta-photoproduction from nuclei in a relativistic impulse approximation approach
• Nuclear dependence of the coherent eta photoproduction reaction in a relativistic approach

Cited by in corpus (8)

• Coherent pi0-photoproduction from atomic nuclei
• Neutrino-induced coherent pion production off nuclei reexamined
• Coherent Neutrinoproduction of Photons and Pions in a Chiral Effective Field Theory for Nuclei
• Quasifree kaon-photoproduction from nuclei in a relativistic approach
• Quasifree eta photoproduction from nuclei and medium modifications of resonances
• Photoproduction of Pseudoscalar Mesons from Nuclei
• Nuclear coherent ${\pi }^0$ photoproduction with charge-exchange and spin-flip rescattering
• Pion-nucleus optical potential valid up to the DELTA-resonance region