Search for η and η′→π+ ^e-ν_̄e+c.c. decays in J/ψ→φη and φη′

Using a sample of 225.3 million J/ψ events collected with the BESIII detector at the BEPCII e⁺e^- collider in 2009, searches for the decays of η and η′→π⁺e ^-ν_̄e+c.c. in J/ψ→φη and φη′ are performed. The φ signals, which are reconstructed in K⁺K^- final states, are used to tag η and η′ semileptonic decays. No signals are observed for either η or η′, and upper limits at the 90% confidence level are determined to be 7.3×10^-4 and 5.0×10^-4 for the ratios B(η→π⁺e^-ν_̄e+c.c.) B(η→π⁺π^-π0) and B(η′→π ⁺e^-ν_̄e+c.c.) B(η′→π⁺π^-η), respectively. These are the first upper-limit values determined for η and η′ semileptonic weak decays.