Asymptotic behavior of nucleon electromagnetic form factors in time-like region
DAPNIA/SPhN, CEA/Saclay, 91191, Gif-sur-Yvette Cedex, France
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Accepted: 11 October 2005
Published online: 17 November 2005
We study the asymptotic behavior of the ratio of Pauli and Dirac electromagnetic nucleon form factors, F 2/F 1, in time-like region, for different parametrizations built for the space-like region. We investigate how fast the ratio F 2/F 1 approaches the asymptotic limits according to the Phragmèn-Lindelöf theorem. We show that the QCD-inspired logarithmic behavior of this ratio results in very far asymptotics, experimentally unachievable. This is also confirmed by the normal component of the nucleon polarization, Py, in e + + e -↦N + ¯ (in collisions of unpolarized leptons), which is a very interesting observable, with respect to this theorem. Finally we observe that the 1/Q parametrization of F 2/F 1 contradicts this theorem.
PACS: 13.40.Gp Electromagnetic form factors – / 13.88.+e Polarization in interactions and scattering – / 13.40.-f Electromagnetic processes and properties –
© Società Italiana di Fisica and Springer-Verlag, 2005