  In order to analyze data on charged pions correlation channels, pi^+(2pi^-)
and pi^-(2pi^+), we propose new interferometry approach using the Coulomb wave
function. We show that to describe adequately data we have to introduce new
parameter describing the contribution of pi^-(k_1) pi^+(k_2) --> pi^-(k_2)
pi^+(k_1) process. Using this new formula we analyze data on pi^+(2pi^-) and
pi^-(2pi^+) channels at sqrt(s) = 91 GeV by DELPHI Collaboration, and estimate
the magnitude of this new parameter as well as the degree of coherence.
