Observation of f1(1285)→π+π−π+π− in radiative decays ☆

Abstract We present an analysis of J ψ →γf 1 (1285) , f 1 (1285)→ π + π − π + π − , using the Mark III detector at SPEAR, based on 5.8 × 10 6 produced J ψ events. We measure B( J ψ →γf 1 (1285) , f 1 (1285)→ π + π − π + π − )=(4.8±1.3±0.9) × 10 −5 . We obtain a new measurement of the absolute branching ratio of J ψ →γf 1 (1285) . The mixing angle of the f 1 (1285) and the f 1 (1420) in the 1 ++ nonet is determined.