Darmstadt 2016 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 63: Hadron Structure and Spectroscopy X

HK 63.6: Vortrag

Freitag, 18. März 2016, 15:30–15:45, S1/01 A4

A Three-Flavor Chiral Effective Model with Four Baryonic Multiplets within the Mirror Assignment — •Lisa Olbrich, Miklós Zétényi, Francesco Giacosa, and Dirk H. Rischke — Institute for Theoretical Physics, Goethe University Frankfurt am Main

Chiral symmetry requires the existence of chiral partners in the hadronic mass spectrum. In this talk, we address the question which is the chiral partner of the nucleon. We employ a chirally symmetric linear sigma model, where hadrons and their chiral partners are treated on the same footing. We construct four spin-1/2 baryon multiplets from left- and right-handed quarks as well as left- and right-handed diquarks. Two of these multiplets transform in a “mirror” way, which allows for chirally invariant mass terms. We then embed these baryonic multiplets into the Lagrangian of the extended Linear Sigma Model, which features (pseudo)scalar and (axial-)vector mesons, as well as glueballs. Reducing the Lagrangian to the two-flavor case, we obtain four doublets of nucleonic states. These mix to produce the positive-parity nucleon N(939) and the Roper resonance N(1440), as well as the negative-parity resonances N(1535) and N(1650). We determine the parameters of the nucleonic part of the Lagrangian from a fit to masses and decay properties of these states. Studying the limit of vanishing quark condensate, we conclude that N(939) and N(1535), as well as N(1440) and N(1650) form pairs of chiral partners.

[1] L. Olbrich, M. Zétényi, F. Giacosa, and D.H. Rischke, arXiv:1511.05035 [hep-ph].