arXiv subjects

C. H. M. van Antwerpen

Publications and source records attributed to C. H. M. van Antwerpen.

2 recordsLinked to original sources

arXiv1994

A gauge invariant unitary theory for pion photoproduction

The Ward-Takahashi identities are central to the gauge invariance of the photoproduction amplitude. Here we demonstrate that unitarity and in particular the inclusion of both the $πN$ and $γπN$ thresholds on equal footing yields a photoproduction amplitude that satisfies both two-body unitarity and the generalized Ward-Takahashi identities. The final amplitude is a solution of a set of coupled channel integral equations for the reactions $πN\rightarrowπN$ and $γN\rightarrowπN$. % Figures available from the authors upon request, % e-mail: phchv@pippin.cc.flinders.edu.au % Submitted to Physical Review C

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arXiv1993

A Gauge Invariant Unitary Theory for Pion Photoproduction

A covariant, unitary and gauge invariant theory for pion photoproduction on a single nucleon is presented. To achieve gauge invariance at the operator level one needs to include both the $πN$ and $γπN$ thresholds. The final amplitude can be written in terms of a distorted wave in the final $πN$ channel provided one includes additional diagrams to the standard Born term in which the photon is coupled to the final state pion and nucleon. These additional diagrams are required in order to satisfy gauge invariance.

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