Excitation cross sections for pionium in the Glauber approximation

The experiment DIRAC at CERN aims to measure the lifetime of relativistic pi(+)pi(-) atoms (pionium) with an accuracy of 10%, requiring cross sections for the interaction of pionium with the target material with an accuracy of 1% as theoretical input. We calculate the excitation cross sections for the Coulomb interaction with the target atoms in the Glauber approximation which takes into account all multi-photon exchange processes. We find that they decrease the excitation cross sections, calculated to first order in the Born approximation, by more than 2-15% for target materials with increasing Z and all initial states, much worse than the desired accuracy of 1%.