Observation of e + e − → π 0 π 0 ψ 2(3823)

Using a data sample corresponding to an integrated luminosity of 11.3 fb−1 collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we observe the process e+e−→ π0π0ψ2(3823) for the first time with a statistical significance of 6.0 standard deviations. The ratio of average cross sections for e+e−→ π0π0ψ2(3823) and π+π−ψ2(3823) is determined to be R=σ[e+e−→π0π0ψ2(3823)]σ[e+e−→π+π−ψ2(3823)]=0.57±0.14±0.05, which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the ψ2(3823) is measured to be M[ψ2(3823)] = 3824.5 ± 2.4 ± 1.0 MeV/c2. Due to the limited data sample, an upper limit of 18.8 MeV at 90% confidence level is set on the intrinsic width of ψ2(3823). [Figure not available: see fulltext.].