ИСТИНА

Theory, using Low Energy QCD, calculated with high precision the pion-pion and pion-kaon scattering length. Lifetime of pi+pi- atoms are related with a difference of pion-pion s-wave scattering lengths with isospin 0 and 2: |a0 - a2|. Energy splitting between p-states (long-lived atoms) and s-states of pi+pi- atoms allows to investigate another combination: |2 a0 + a2|. Lifetime of piK atom gives information about difference of pion-kaon s-wave scattering lengths with isospin 1/2 and 3/2: |a1/2 - a3/2|. Experimental measurements of pion-pion and pion-kaon lifetimes and observation of long-lived pi+pi- atoms at experiment DIRAC are presented.