Abstract
Abstract We give the electromagnetic corrections (due to the mass difference between π ± and π 0 and the Coulomb potential) to the s-wave threshold parameters in the coupled two-channel ( π + π − , π 0 π 0 ) system. We estimate that the uncertainty in this correction to the threshold charge-exchange amplitude (which determines the lifetime of pionium, i.e. the π + π − bound state) is rather less than the uncertainty in the prediction of chiral perturbation theory for this quantity. We conclude that a measurement of the lifetime for the decay of pionium with an accuracy of about 10% would provide a significant test of the chiral-perturbation theory prediction.
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