The investigation of K+π−, π+K− and π+π− atoms

Abstract

Theory, using Low Energy QCD, predicts with high precision the pion-pion and pion-kaon scattering lengths. There is accurate relation between K+π− and π+K− atoms lifetime and pion-kaon S-wave scattering lengths with isospin 1/2 and 3/2. Experiment DIRAC at CERN PS detects 345 ± 61 pairs from K+π− and π+K− atoms breakup. It allows to achieve the first observation of exotic atoms consisted of pion and kaon. Measured values of πK 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.