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Paramagnetic effect of light quark loops on Chiral Symmetry Breaking

Sebastien Descotes, Luca Girlanda, Jan Stern

hep-pharXiv:hep-ph/9910537

Abstract

We argue that light quark loops produce a paramagnetic suppression of infrared-sensitive order parameters such as <qq>, as the number Nf of light fermions increases. The possibly strong dependence of <qq> on Nf is related to the observed Zweig rule violation in the scalar channel. Presuming the existence of a chiral phase transition for not too large Nf, we discuss the phenomenological possibilities of separately determining the two-flavour and three-flavour condensates and the quark mass ratio r=2ms/(mu+md). The issue is closely related to the interpretation of new forthcoming precise pi-pi data at low energy.

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