Calculation of Screening Masses in a Chiral Quark Model
  We consider a simple model for the coordinate-space vacuum polarization function which is often parametrized in terms of a screening mass. We discuss the circumstances in which the standard result for the screening mass, $m_{sc}=\pi T$, is obtained. In the model considered here, that result is obtained when the momenta in the relevant vacuum polarization integral are small with respect to the first Matsubara frequency. 
Xiangdong Li, Hu Li, C. M. Shakin, and Qing Sun