Three-pion coherent production in π−d interactions at 21 GeV/c

We present an analysis of 3π coherent production in the reaction π−d→π−π−π+d at 21 GeV/c, using a sample of 4552 events. We find the cross section for the process is 517 ± 27 μb, and discuss the effective-mass distributions of the 3π, 2π and dπ systems. The 3π mass distribution is dominated by the A1 enhancement, with no evidence for A2 production and only a shoulder at the A3. The (2π)0 mass distributions are dominated by ϱ and f production.