Charged pion polarizability in the nonlocal quark model of   Nambu-Jona-Lasinio type
  The polarizability of a charged pion is estimated in the framework of the nonlocal chiral quark model of the Nambu--Jona-Lasinio type. Nonlocality is described by quark form factors of the Gaussian type. It is shown that the polarizability in this model is very sensitive to the form of nonlocality and choice of the model parameters. 
A. E. Radzhabov and M. K. Volkov