Observation of ψ(3686)→η^′e⁺e⁻

Using a data sample of 448.1×10⁶ ψ(3686) events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay ψ(3686)→η^′e⁺e⁻, with significances of 7.0σ and 6.3σ when reconstructing the η^′ meson via its decay modes η^′→γπ⁺π⁻ and η^′→π⁺π⁻η (η→γγ), respectively. The weighted average branching fraction is determined to be B(ψ(3686)→η^′e⁺e⁻)=(1.90±0.25±0.11)×10⁻⁶, where the first uncertainty is statistical and the second systematic.