Exclusive quasifree pion photoproduction on complex nuclei in the Δ region

Li, Xiaodong; Wright, L. E.; Bennhold, C.

doi:10.1103/physrevc.48.816

Cited by 39 publications

(17 citation statements)

References 25 publications

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“…9 is therefore a result of the relativistic, non-local treatment of the production operator. In a non-relativistic framework non-local effects have been shown to be important in the photoproduction of charged pions in [28,29].…”

Section: Resultsmentioning

confidence: 99%

“…In the case of coherent production, however, both the incoming and the outgoing nucleon are in a bound state, so that they do not have a well defined asymptotic momentum. The validity of the local approximation for the photoproduction of charged pions is is discussed in [28,29]. To avoid the uncertainties related to the local approximation, we evaluate the matrix elements of the production operator non-locally.…”

Section: B Photoproduction On the Nucleusmentioning

confidence: 99%

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Coherent photoproduction of pions on spin-zero nuclei in a relativistic, non-local model

1998

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A relativistic and non-local model for the coherent photoproduction of pions on spin-zero nuclei is presented. The production operator is derived from an effective Lagrangian model that contains all the degrees of freedom known to contribute to the elementary process. Using the framework of DWIA, the matrix elements of this operator are evaluated using relativistic bound state wave functions. Final state interactions are accounted for via a pion-nucleus optical potential. The effects of in-medium modifications of the production operator are discussed. We give results for 12 C and 40 Ca, and compare our calculations to the data of the A2 collaboration at MAMI.

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Section: Resultsmentioning

confidence: 99%

Section: B Photoproduction On the Nucleusmentioning

confidence: 99%

Coherent photoproduction of pions on spin-zero nuclei in a relativistic, non-local model

1998

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“…A similar formula for the local approximation has been given in [13]. This approximation is widely used in DWIA calculations, in a nonrelativistic framework its validity has been studied in the photoproduction of charged pions in [14,15]. In this context, the ω-exchange plays a special role.…”

Section: Photoproduction On the Nucleusmentioning

confidence: 96%

“…We now read off from Eqs. (10), (14) and (15) that the local approximation corresponds in position space to the replacement:…”

Section: Photoproduction On the Nucleusmentioning

confidence: 99%

Coherent photoproduction of eta-mesons on spin-zero nuclei in a relativistic, non-local model

1998

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The coherent photoproduction of η-mesons on spin-zero nuclei is studied in a relativistic, non-local model, which we have previously applied to the coherent photoproduction of pions. We find that different off-shell extrapolations of the elementary production operator lead to large effects in the cross section. We also show that the almost complete suppression of the N (1535) seen in earlier studies on this reaction is a result of the local or factorization approximation used in these works. Non-local effects can lead to a considerable contribution from this resonance. The relative size of the N (1535) contribution depends on the structure of the nucleus under consideration. We give an estimate for the contribution of the N (1520) resonance and discuss the effect of an η-nucleus optical potential.

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“…In this scheme, the reliability of any reaction model counts on the soundness of the model framework and on the fulfillment of the symmetries of the underlying theory. Following this reasoning, the reliability of a complex calculation on nuclei starting from an elementary reaction model (e.g., meson exchange currents [1] or pion photoproduction from nuclei starting from a model on pion photoproduction from the nucleon [2]) relies on how sound is the theoretical background used in the construction of the elementary reaction model. At tree level, the invariant amplitudes we obtain from the effective Lagrangians are real.…”

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confidence: 99%

Crossing symmetry and phenomenological widths in effective Lagrangian models of the pion photoproduction process

2008

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We investigate the importance of crossing symmetry in effective field models and the effects of phenomenological nucleon resonance widths on the paradigmatic case of pion photoproduction. We use reaction models containing four star resonances up N(1720)) with different prescriptions for crossed terms and widths, to fit the latest world database on pion photoproduction. We compare χ 2 results from selected multipoles and fits. The χ 2 is highly dependent on the fulfillment of crossing symmetry and the inclusion of u channels.

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Exclusive quasifree pion photoproduction on complex nuclei in the Δ region

Cited by 39 publications

References 25 publications

Coherent photoproduction of pions on spin-zero nuclei in a relativistic, non-local model

Coherent photoproduction of pions on spin-zero nuclei in a relativistic, non-local model

Coherent photoproduction of eta-mesons on spin-zero nuclei in a relativistic, non-local model

Crossing symmetry and phenomenological widths in effective Lagrangian models of the pion photoproduction process

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