Propagator of the Δ resonance and determination of the magnetic moment of the Δ+ from the γpγπop reaction

A. I. Machavariani and Amand Faessler
Phys. Rev. C 72, 024002 – Published 19 August 2005

Abstract

The photon-proton scattering reactions γpπop,γpγp, and γpγπop are investigated in the framework of the three-dimensional time-ordered approach using different models of the on-shell Δ propagators. These Δ propagators are taken from the unitary separable models of the πN elastic-scattering amplitude and from the relativistic Breit-Wigner shape representation of the nonunitary πN amplitude in the tree approach. The numerical calculations are performed with the complete set of the one-particle (π,ω,andρ-meson, nucleon, and Δ) exchange diagrams. It is found that the numerical calculations of the above reactions in the Δ-resonance region are very sensitive to the model of the Δ propagator. This sensitivity is explained by the difference between the input πN elastic-scattering observables used for the construction of the Δ propagator. It is shown, that after additional approximation our calculations reproduce the tree-level model calculations with the Breit-Wigner shape Δ propagator. This model is in good agreement with the γpπo'p' reaction and with the preliminary data for the γpγ'πo'p' reaction. Conversely, it is demonstrated, that the relativistic Breit-Wigner shape Δ propagators, obtained from the nonunitary πN amplitudes in the tree approximation, is inconsistent to apply for reproduction of the γp scattering observables because they do not describe the πN scattering data in the Δ resonance region. It is emphasized, that to extract the magnitude of the Δ+ magnetic moment from the cross sections of the γpγ'π'N' reaction it is necessary to fix the form of the Δ propagator based on the unified description of the two body πpπN,γpπN basic channels together with the essential γpππN and γpγp reactions.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
9 More
  • Received 9 December 2003

DOI:https://doi.org/10.1103/PhysRevC.72.024002

©2005 American Physical Society

Authors & Affiliations

A. I. Machavariani1,2,3 and Amand Faessler1

  • 1Institute für Theoretische Physik der Universität Tübingen, D-72076 Tübingen, Germany
  • 2Joint Institute for Nuclear Research, Dubna, Moscow Region RU-141980, Russia
  • 3High Energy Physics Institute of Tbilisi State University, University str. 9, Tbilisi 380086, Georgia

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 72, Iss. 2 — August 2005

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review C

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×