Study of the radiative decayJ/ψ→γρρ

We present an analysis of the decay J/{ψ}{→}{γ}4{π} in the final states {γ}π⁺{{π}}^{{{-}}}π⁺{{π}}^{{{-}}}and γ{{π}}⁺π⁰{{π}}^{{{-}}}π⁰. The branching fractions obtained are B(J/{ψ}{→}{γ}π⁺{{π}}^{{{-}}}π⁺{{π}}^{{{-}}})= (3.05±0.08±0.45)×{10}^{{{-}}3}and B(J/ψ→γ{{π}}⁺π⁰{{π}}^{{{-}}}πᵒ)=( 8.3±{}0.2±{}3.1)×{}10^-3 for m_4π less than 2 GeV/c². The 4{π} invariant-mass distributions extend from 1.0 to 3.0 GeV/c², showing peaks at approximately 1.55 and 1.8 GeV/c². In an analysis of the 4{π} final state we find that {}50% of the events below 2 GeV/c² are pseudoscalar {ρ}{ρ}, the product branching fraction of which is determined to be {→}{ρ}{ρ})= (4.7±{}0.3±{}0.9)×{}10^-3. No other significant {ρ}{ρ} component is found, and upper limits on the product branching fraction B(J/{ψ}{→}{γ}X)B(X{→}{ρ}{ρ}) are presented for the theta(1690) and the gT states near 2.2 GeV/c².