Relativistic corrections to the pionium lifetime - art. no. 077506

Next to leading order contributions to the pionium lifetime are considered within non-relativistic effective field theory. A more precise determinatio n of the coupling constants is then needed in order to be consistent with t he relativistic pi-pi scattering amplitude which can be obtained from chira l perturbation theory. The relativistic correction is found to be 4.1% and corresponds simply to a more accurate value for the non-relativistic decay momentum.