Observation and investigation of πK atoms

Abstract

There is accurate relation between lifetime of atoms, consisting of pion and kaon, and a difference of S-wave pion kaon scattering length with isospin 1/2 and 3/2: |a1/2 - a3/2 |. This difference is predicted by low energy QCD. Experiment DIRAC at CERN PS detects 349 ± 62 pairs from K+π− and π+K− atoms and make observation of exotic atoms consist of pion and kaons and provides way for measurement of pion-kaon scattering length difference and check of theoretical predictions.