Eur. Phys. J. A (2005) 26: 107-123
https://doi.org/10.1140/epja/i2005-10154-7

Original Article

Precision calculation of γd↦πnn within chiral perturbation theory

¹ Institut für Kernphysik (Theorie), Forschungszentrum Jülich, D-52425, Jülich, Germany
² Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117259, Moscow, Russia
³ Helmholtz-Institut für Strahlen- und Kernphysik (Theorie), Universität Bonn, Nußallee 14-16, D-53115, Bonn, Germany

^* e-mail: c.hanhart@fz-juelich.de

Received: 13 June 2005
Accepted: 9 September 2005
Published online: 9 November 2005

Abstract

The reaction γd↦π⁺ nn is calculated up to order χ^5/2 in chiral perturbation theory, where χ denotes the ratio of the pion to the nucleon mass. Special emphasis is put on the role of nucleon recoil corrections that are the source of contributions with fractional power in χ. Using the known near-threshold production amplitude for γp↦π⁺ n as the only input, the total cross-section for γd↦π⁺ nn is described very well. A conservative estimate suggests that the theoretical uncertainty for the transition operator amounts to 3% for the computed amplitude near threshold.