ИСТИНА

Theory, using Low Energy QCD, predicts with high precision the pion-pion and pion-kaon scattering lengths. There is accurate relation between pi+pi- atom lifetime and a difference of S-wave pion-pion scattering lengths with isospin 0 (a_0) and 2 (a_2). Similar relation exists for K+pi- and pi+K- atoms lifetime and pion-kaon scattering lengths with isospin 1/2 $a_1/2) and 3/2 (a_3/2). Experiment DIRAC at CERN PS detects 345+-61$ pairs from K+pi- and pi+K- atoms breakup. It allows to achieve the first observation of exotic atoms consisted of pion and kaon. Measured values of piK atom lifetime and corresponding pion-kaon scattering length difference are presented. It is shown, that experimental accuracy for pion-kaon scattering length difference could be significantly improved with an experiment at SPS energy. The experimental observation of the long-lived pi+pi- atoms is shown. The scheme to use the obtained data for the long-lived atom lifetime measurement will be described. Possibility of the long-lived pi+pi- atom Lamb shift measurement and evaluation of pion-pion scattering length new combination (|2*a_0+a_2|) is discussed.