The pion-induced pion-production reaction (π+, π+π−) on 4He has been studied at an incident pion kinetic energy of 280 MeV. The outgoing pions were detected in coincidence and the measured four-fold differential cross sections are compared with a quasifree πN → ππN microscopic model. Finally, the results are directly compared with recent data from the 16O(π+, π+π−) and2H(π+, π+π−)pp reaction at the same incident energy.
