Backward pion photoproduction

A. Sibirtsev; J. Haidenbauer; F. Huang; S. Krewald; U. -G. Meißner

doi:10.1140/epja/i2008-10743-x

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Hadrons and Nuclei

Eur. Phys. J. A (2009) 40: 65-75
https://doi.org/10.1140/epja/i2008-10743-x

Regular Article - Theoretical Physics

Backward pion photoproduction

A. Sibirtsev¹^,2, J. Haidenbauer³^,4, F. Huang³^,a, S. Krewald³^,4^* and U. -G. Meißner¹^,3^,4

¹ Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn, D-53115, Bonn, Germany
² Excited Baryon Analysis Center (EBAC), Thomas Jefferson National Accelerator Facility, 23606, Newport News, VA, USA
³ Institut für Kernphysik and Jülich Centre for Hadron Physics, Forschungszentrum Jülich, D-52425, Jülich, Germany
⁴ Institute for Advanced Simulations, Forschungszentrum Jülich, D-52425, Jülich, Germany

^* e-mail: s.krewald@fz-juelich.de

Received: 27 November 2008
Accepted: 3 March 2009
Published online: 31 March 2009

Abstract

We present a systematic analysis of backward pion photoproduction for the reactions $\gamma$ p $\rightarrow$ $\pi^{0}_{}$ p and $\gamma$ p $\rightarrow$ $\pi^{+}_{}$ n . Regge phenomenology is applied at invariant collision energies above 3GeV in order to fix the reaction amplitude. A comparision with older data on $\pi^{0}_{}$ - and $\pi^{+}_{}$ -photoproduction at $\vartheta$ = 180^° indicates that the high-energy limit as given by the Regge calculation could be reached possibly at energies of around $\sqrt{{s}}$ ≃ 3 GeV. In the energy region of $\sqrt{{s}}$ $\le$ 2.5 GeV, covered by the new measurements of $\gamma$ p $\rightarrow$ $\pi^{0}_{}$ p differential cross-sections at large angles at ELSA, JLab, and LEPS, we see no clear signal for a convergence towards the Regge results. The baryon trajectories obtained in our analysis are in good agreement with those given by the spectrum of excited baryons.