First measurements of timelike form factors of the hyperons, Λ0, Σ0, Σ+, Ξ0, Ξ−, and Ω−, and evidence of diquark correlations

Abstract

Using 805 pb−1 of e+e− annihilation data taken with the CLEO-c detector at ψ(3770), s=3770 MeV, we report the first measurements of the electromagnetic form factors of the Λ0, Σ0, Σ+, Ξ0, Ξ−, and Ω− hyperons for the large timelike momentum transfer of |Q2|=14.2 GeV2. The form factors for the different hyperons are found to vary by nearly a factor two. It is found that |GM(Λ0)|=1.66(24)×|GM(Σ0)|. The Λ0 and Σ0 hyperons have the same uds quark content, but differ in their isospin, and therefore the spin of the ud quark pair. It is suggested that the spatial correlation implied by the singlet spin–isospin configuration in the Λ0 is an example of strong diquark correlations in the Λ0, as anticipated by Jaffe and Wilczek. Improved measurements of the branching fractions of ψ(2S)→pp¯ and hyperon–antihyperon pairs are also reported.