Bochum 2009 – scientific programme

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HK: Fachverband Hadronen und Kerne

HK 4: Hadron Structure and Spectroscopy I

HK 4.5: Talk

Monday, March 16, 2009, 15:30–15:45, H-ZO 20

Gauge-invariant coupling to spin-3/2 resonances. — •Vitaly Shklyar, Horst Lenske, and Ulrich Mosel — Institut für Theoretische Physik, Universität Giessen, Germany

A gauge invariant interaction of the Δ-resonance to the final π N and γ N is discussed. It is shown that the gauge-invariant coupling invented by Pascalutsa eliminates ’off-shell’ degrees of freedom only for the Rarita-Schwinger propagator but fails in the general case. The origin of the problem is discussed and a generalized gauge-invariant coupling is deduced. Finally, the full Lagrangian depends on one free parameter which reflects a freedom in choosing an ’off-shell’ content of the theory. The calculated π N scattering amplitude shows no dependency on the specific choice of the parameter. This reflect the fact that physical observables do not depend on any ’off-shell’ contributions and do not depend on the free parameter of Lagrangian.
Work supported by DFG.