Relationship of pionium lifetime with pion scattering lengths in   generalized chiral perturbation theory
  The pionium lifetime is calculated in the framework of the quasipotential-constraint theory approach, including the sizable electromagnetic corrections. The framework of generalized chiral perturbation theory allows then an analysis of the lifetime value as a function of the pion S-wave scattering lengths with isospins I=0,2, the latter being dependent on the quark condensate value. 
H. Sazdjian (Univ. of Orsay, France)