A

The reaction π−p ⇒ π−π−π+p has been investigated at 40 GeV/c incident momentum in the momentum transfer interval 0.04 < t < 0.33 (GeV/c)2. Analysing the decay of the 3π system by a partial‐wave method, the parameters, the differential cross‐section, and the polarization of the abundantly produced A1 and A2 mesons are obtained. From the interference between the different partial waves, a resonance behaviour is found for the A2 meson but not for the A1 meson.