Erlangen 2001 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 21: Theorie III

HK 21.3: Vortrag

Dienstag, 20. März 2001, 17:00–17:15, B

Pion and Kaon Self-energies in Asymmetric Nuclear Matter — •Norbert Kaiser und Wolfram Weise — Physik-Department, Technische Universität München

We use chiral perturbation theory at finite baryon density to calculate systematically the self-energies of pions and kaons in asymmetric nuclear matter. At the two-loop level we find three types of corrections which go beyond the well-known linear density approximation. These are: 1) relativistic corrections from the pseudovector Born terms, 2) double scattering as given by the chiral meson-baryon interaction vertex and 3) effects induced by the chiral 4-meson vertex with the two virtual mesons being absorbed on the nucleons in the Fermi-sea. The resulting mass-shift for a π⁻ in the center of a heavy nucleus as Pb is Δ m_π⁻≃ 14 MeV, i.e. somewhat smaller than what is needed to support deeply bound pionic atom-states. The π⁺ mass-shift in ³H (assuming an effective density of 0.05 fm⁻³) is Δ m_π⁺≃ −3  MeV. This is consistent with an analysis of π⁺-electroproduction from ³He measured at MAMI. Finally, we find a 9% increase of the K⁺ mass at normal nuclear matter density. This is consistent with the interpretation of the K⁺/K⁻ yields in heavy ion collisions measured at GSI. Supported in part by GSI