Study of the pionic correlations in pn → π+2π− annihilation at rest

The experimental 2π correlations in pn → π+2π− annihilation at rest are studied as a function of the four-momentum transfer Q. The normalized ratio between the 2π− and π+π− distributions show a maximum at Q = 0 GeV/c with height h2 ∼ 7. The study of the amplitude suggests that this height is due to two contributions having about the same strength: one is the Bose-Einstein statistics, the other is the positive interference between I = 0 and I = 1 2π resonances.