Radiative decay ofJ/ψ into γ π+ π−

The radiative decayJ/ψ → γ π+ π− has been studied using the 8.6 millionJ/ψ produced in the DM2 experiment at the DCIe+e− storage rings at Orsay. The π+ π− mass spectrum shows a cleanf2 (1270) signal, and the possible presence of two other states at thef2 (1720) andf4 (2030) masses. For thef2 (1270), the branching ratio BR(J/ψ →γf)xBR(f→π+ π−) is measured to be (7.50±0.30±1.12)×10−4, and the spin analysis prefers theJ=2 assignment, with helicity parametersx=0.83±0.06 andy=0.01±0.06. The existence of higher mass states is discussed.