  The charge or barion number balance function in the relative azimuthal angle
of a pair of particles emitted in ultrarelativistic heavy ion collisions is
studied. The pi+pi- and ppbar balance functions are computed using thermal
models with two different set of parameters, corresponding to a large
freeze-out temperature and a moderate transverse flow or a small temperature
and a large transverse flow. The single particle spectra including pions from
resonance decays are similar for the two scenarios, on the other hand the
azimuthal balance function is very different and could serve as an independent
measure of the transverse flow at the freeze-out.
