Angular Correlations in gamma Gamma ---> rho0 rho0 Near Threshold

We present an analysis ofρ0ρ0 production by two photons in theρ0ρ0 invariant mass range from 1.2 to 2.0 GeV. From a study of the angular correlations in the process γγ→ρ0ρ0→π−π+π− we exclude a dominant contribution fromJP=0− or 2− states. The data indicate sizeable contributions fromJP=0+ for four pion massesM4π<1.7 GeV and fromJP=2+ forM4π>1.7 GeV. The data are also well described by a model with isotropic production and uncorrelated isotropic decay of theρ0,s. The cross section stays high below the nominalρ0ρ0 threshold, i.e.M4π<1.5 GeV. The matrix element forρ0ρ0 production is found to decrease steeply with increasingM4π. Upper limits for the couplings of the ι(1440) and Θ(1640) to γγ andρ0ρ0 are given:Γ(ι→γγ)·B(ι→ρ0ρ0)<1.0 keV andΓ(Θ→γγ)

ELECTRON POSITRON: COLLIDING BEAMS
COLLIDING BEAMS: ELECTRON POSITRON
ELECTRON POSITRON: INELASTIC SCATTERING
INELASTIC SCATTERING: ELECTRON POSITRON
PHOTON PHOTON: INTERACTION
INTERACTION: PHOTON PHOTON
EXCHANGE: TWO-PHOTON
TWO-PHOTON: EXCHANGE
RHO(770)0: ELECTROPRODUCTION
ELECTROPRODUCTION: RHO(770)0

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