Study of the radiative decayJ/ψ→γρρ

Abstract

We present an analysis of the decay J/ψ→γ4π in the final states γ${\pi }^{+}$ ${\pi }^{\mathrm{-}}$ ${\pi }^{+}$ ${\pi }^{\mathrm{-}}$ and γ${\pi }^{+}$ ${\pi }^0$ ${\pi }^{\mathrm{-}}$ ${\pi }^0$. The branching fractions obtained are B(J/ψ→γ${\pi }^{+}$ ${\pi }^{\mathrm{-}}$ ${\pi }^{+}$ ${\pi }^{\mathrm{-}}$)= (3.05±0.08±0.45)×${10}^{\mathrm{-}3}$ and B(J/ψ→γ${\pi }^{+}$ ${\pi }^0$ ${\pi }^{\mathrm{-}}$ ${\pi }^o$)=( 8.3±0.2±3.1)×${10}^{\mathrm{-}3}$ for $m_{4\pi }$ less than 2 GeV/$c^2$. The 4π invariant-mass distributions extend from 1.0 to 3.0 GeV/$c^2$, showing peaks at approximately 1.55 and 1.8 GeV/$c^2$. In an analysis of the 4π final state we find that ≊50% of the events below 2 GeV/$c^2$ are pseudoscalar ρρ, the product branching fraction of which is determined to be &→ρρ)= (4.7±0.3±0.9)×${10}^{\mathrm{-}3}$. No other significant ρρ component is found, and upper limits on the product branching fraction B(J/ψ→γX)B(X→ρρ) are presented for the theta(1690) and the $g_T$ states near 2.2 GeV/$c^2$.