München 2019 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 10: Hadron Structure and Spectroscopy II

HK 10.6: Vortrag

Montag, 18. März 2019, 18:00–18:15, HS 13

Spectral functions of electromagnetic and axial nucleon form factors: 3π-continua at low energies — •Norbert Kaiser¹ and Emilie Passemar² — ¹Physik Department T39, TU München — ²Department of Physics, Indiana University, Bloomington, USA

We study the imaginary parts of the isoscalar electromagnetic and isovector axial form factors of the nucleon close to the 3π-threshold in covariant baryon chiral perturbation theory. At the two-loop level, the contributions arising from leading and next-to-leading order chiral π N-vertices, as well as pion-induced excitations of virtual Δ(1232)-isobars, are calculated. It is found that the heavy baryon treatment overestimates substantially these 3π-continua. From a phenomenological analysis, that includes the narrow ω(783)-resonance or the broad a₁-resonance, one can recognize small windows near threshold, where chiral 3π-dynamics prevails. However, in the case of the isoscalar electromagnetic form factors G_E,M^s(t), the radiative correction provided by the π⁰γ-intermediate state turns out to be more significant therein.
Work supported in part by DFG and NSFC (CRC110).