In-mediumππcorrelation induced by partial restoration of chiral symmetry

Abstract

The purposes of the present paper are twofold: Firstly, we show that the near-threshold enhancement in the I = J = 0 channel in nuclear matter takes place irrespective of the representations (linear or non-linear) of chiral symmetry, if the effect of partial restoration of chiral symmetry in the medium is properly incorporated. Secondly, we show that L (2) , which is a next-to-leading order term in the non-linear chiral lagrangian in the heavy-baryon formalism, gives relevant vertices for the near-threshold enhancement in the I=J=0 channel. Such vertices have not been taken into account in previous calculations of the in-medium ππ scattering in the non-linear lagrangian approaches. Let us first consider the ππ scattering in nuclear matter in the SU(2) LσM to demonstrate the essential idea of the near-threshold enhancement. The following argument is slightly different from the original one [4] but is easy to be generalized to the non-linear case. The lagrangian adopted in [4] is the standard Gell-Mann-Levy model with a minor modification