Observation of η′ Decays to π+ π- π0 and π+ π- e+ e-

Using psi(2S) -> pi(+) pi(-) J/psi, J/psi -> gamma eta' events acquired with the CLEO-c detector at the CESR e(+) e(-) collider, we make the first observations of the decays eta' -> pi(+) pi(-) pi(0) and eta' -> pi(+) pi(-) e(+) e(-), measuring absolute branching fractions (37(-9)(+11) +/- 4) x 10(-4) and (25(-9)(+12) +/- 5) x 10(-4), respectively. For eta' -> pi(+) pi(-) pi(0), this result probes the mechanism of isospin violation and the roles of pi(0)/eta/eta'-mixing and final state rescattering in strong decays. We also set upper limits on branching fractions for eta' decays to pi(+) pi(-) mu(+) mu(-), 2(pi(+) pi(-)), pi(+) pi(-) 2 pi(0), 2(pi(+) pi(-))pi(0), 3(pi(+) pi(-)), and invisible final states.