Dresden 2013 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 73: Hadronenstruktur und -spektroskopie

HK 73.1: Gruppenbericht

Donnerstag, 7. März 2013, 16:45–17:15, HSZ-105

Pion photo- and electroproduction in effective field theory — •Marius Hilt¹, Stefan Scherer¹, Lothar Tiator¹, and Jambul Gegelia² — ¹Institut für Kernphysik, Universität Mainz — ²Institut für Theoretische Physik II, Ruhr-Universität Bochum

We present a calculation of pion photo- and electroproduction on the nucleon in manifestly Lorentz-invariant baryon chiral perturbation theory up to and including chiral order q⁴. With the results we analyze the new π⁰ p photoproduction data in the threshold region obtained at the Mainz Microtron. In the calculation of observables and the fit of the low-energy constants, we take S, P, and D waves into account. We compare the results for the multipoles with the corresponding single-energy analysis. Furthermore, we also fit the (q⁴) heavy baryon chiral perturbation theory calculation and compare both results. In a second approach we include vector mesons as explicit degrees of freedom in one-loop contributions up to order q³ in order to improve the description for the electroproduction process. We compare this approach and the q⁴ calculation with existing data of pion electroproduction in the threshold region. We provide predictions for several polarization observables for future experiments.