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HK: Fachverband Physik der Hadronen und Kerne

HK 4: Hadronenstruktur und -spektroskopie I

HK 4.2: Gruppenbericht

Montag, 15. März 2010, 17:00–17:30, HG III

Electromagnetic form factors of the Δ(1232) resonance — •Tim Ledwig¹, Jorge Martin Camalich², Vladimir Pascalutsa¹, and Marc Vanderhaeghen¹ — ¹Institut für Kernphysik, Universität Mainz, Germany — ²Departamento de Fisica Teorica and IFIC, Universidad de Valencia-CSIC, Spain

After the nucleon, the Δ(1232) resonance is the most important baryon in hadron physics. However, due to its short life time most of its fundamental properties are experimentally still poorly known. Quantities such as the electric and magnetic moments are inaccesible to usual methods and can only be measured in an indirect way. Only in recent years, a value for the Δ⁺ magnetic dipole moment was extracted from a measurement at the Mainzer Microtron accelerator facility MAMI. Further, a new experiment at MAMI is expected to give soon improved results. On the theoretical side, several lattice groups started to extract Δ electromagnetic properties. Eventhough lattice calculations are regarded as an approach from first principles, they are presently still restricted to unphysical quark masses. A proper chiral extrapolation will be needed to confront these results with experiments. In this presentation we discuss the recent progress of such an extrapolation. For this, we use the framework of the relativistic chiral effective field theory where the Δ is incorporated with the δ-counting scheme. Observables in question are the electric quadrupole, magnetic dipole and magnetic octupole moments.