### 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 (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 5. 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.

Original language | English |
---|---|

Number of pages | 1 |

Journal | Physical Review C - Nuclear Physics |

Volume | 60 |

Issue number | 5 |

DOIs | |

Publication status | Published - 1 Jan 1999 |

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### ASJC Scopus subject areas

- Nuclear and High Energy Physics

### Cite this

*Physical Review C - Nuclear Physics*,

*60*(5). https://doi.org/10.1103/PhysRevC.60.054606

**Lessons to be learned from the coherent photoproduction of pseudoscalar mesons.** / Aburaddad, Laith; Piekarewicz, J.; Sarty, A. J.; Rego, R. A.

Research output: Contribution to journal › Article

*Physical Review C - Nuclear Physics*, vol. 60, no. 5. https://doi.org/10.1103/PhysRevC.60.054606

}

TY - JOUR

T1 - Lessons to be learned from the coherent photoproduction of pseudoscalar mesons

AU - Aburaddad, Laith

AU - Piekarewicz, J.

AU - Sarty, A. J.

AU - Rego, R. A.

PY - 1999/1/1

Y1 - 1999/1/1

N2 - 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 (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 5. 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.

AB - 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 (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 5. 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.

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U2 - 10.1103/PhysRevC.60.054606

DO - 10.1103/PhysRevC.60.054606

M3 - Article

VL - 60

JO - Physical Review C - Nuclear Physics

JF - Physical Review C - Nuclear Physics

SN - 0556-2813

IS - 5

ER -