  The interference fragmentation function translates the fragmentation of a
quark with a transverse projection of the spin into an azimuthal asymmetry of
two final-state hadrons. In e+e- annihilation the product of two interference
fragmentation functions is measured. We report nonzero asymmetries for pairs of
charge-ordered pi+pi- pairs, which indicate a significant interference
fragmentation function in this channel. The results are obtained from a 672
fb-1 data sample that contains 711 \times 106 pi+pi- pairs and was collected at
and near the ?(4S) resonance, with the Belle detector at the KEKB
asymmetric-energy e+e- collider.
