Erlangen 2001 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 10: Postersitzung: Theorie
HK 10.7: Poster
Tuesday, March 20, 2001, 10:30–12:45, R
Pion Charge Radius from Charged Pion Electroproduction — •Veronique Bernard1, Norbert Kaiser2 und Ulf-G. Meißner3 — 1Laboratoire de Physique Theorique, Universite Louis Pasteur, Strasbourg — 2Physik-Department, Technische Universität München — 3Institut für Kernphysik (Theorie), Forschungszentrum Jülich
We analyze a low-energy theorem for threshold pion electroproduction which allows one the extract the charge radius of the pion [1]. We show that at the same order where the pion radius enters, pion loops induce a correction to the momentum dependence of the longitudinal dipole amplitude L0+(−). This model-independent correction amounts to an increase of the pion charge radius squared from the electroproduction data, rπ2 → rπ2 = rπ2 +(3/32 fπ2)(16/π2−1), by about 0.26 fm2. This sheds light on the apparent discrepancy between the recent determination of the pion radius from π+-electroproduction [2] and the one based on elastic pion-electron scattering.
[1] V. Bernard, N, Kaiser, Ulf-G. Meißner, Phys.Rev.C62 028201 (2000).
[2] A. Liesenfeld et al., Phys. Lett. B468, 20 (1999). Supported in part by BMBF and DFG