Abstract

The hadronic pi(+)pi(-) atom is studied in the relativistic perturbative approach based on the Bethe-Salpeter equation. The general expression for the atom lifetime is derived. Lowest-order corrections to the relativistic Deser-type formula for the atom lifetime are evaluated within chiral perturbation theory. The lifetime of the pi(+)pi(-) atom in the two-loop order of chiral perturbation theory is predicted to be tau(1)=(3.03+/-0.10) x 10(-15) s. [S0556-2821(98)07919-3].