Göttingen 1997 – scientific programme

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HK: Hadronen und Kerne

HK 55: Struktur von Baryonen und Mesonen VI

HK 55.4: Group Report

Wednesday, March 26, 1997, 18:15–18:45, HS I

In–Medium Pion Weak Decay from Chiral Perturbation Theory — •Mariana Kirchbach¹ and Andreas Wirzba² — ¹Institut f"ur Kernphysik, Universit"at Mainz, D-55099 Mainz, Germany — ²Institut f"ur Kernphysik, TH Darmstadt, D-64289 Darmstadt, Germany

Two–point functions related to the pion weak decay constant f_π are calculated from the generating functional of chiral perturbation theory in the mean–field approximation and the heavy–baryon limit [1]. The aim is to demonstrate that Lorentz invariance is violated in the presence of background matter. This fact manifests itself in the splitting of both f_π and the pion mass into uncorrelated time– and spacelike parts. We emphasize the different in–medium renormalizations of the correlation functions, show the inequivalence between the in–medium values of f_π deduced from Walecka–type models, on the one hand, and QCD sum rules, on the other hand, and elaborate on the importance for some nuclear physics observables [2].

[1] M. Kirchbach and A. Wirzba, Nucl. Phys. A604 (1996) 395.

[2] M. Kirchbach and A. Wirzba, hep-ph/9609291.