engleski

Baryon transition form factors at the pole

Electromagnetic resonance properties are uniquely defined at the pole and do not depend on the separation of the resonance from background or the decay channel. Photon-nucleon branching ratios are nowadays often quoted at the pole, and we generalize the considerations to the case of virtual photons. We derive and compare relations for nucleon to baryon transition form factors both for the Breit- Wigner and the pole positions. Using the MAID2007 and SAID SM08 partial wave analyses of pion electroproduction data, we compare the GM, GE, and GC form factors for the Delta(1232) resonance excitation at the Breit- Wigner resonance and pole positions up to Q2 = 5 GeV2. We also explore the E/M and S/M ratios as functions of Q2. For pole and residue extraction, we apply the Laurent + Pietarinen method.

transition form factors, Delta resonance, L+P expansion

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