The prediction of the behaviour of Λ-hyperon electromagnetic form factors

Abstract

The behaviour of the Λ-hyperon electric and magnetic form factors is predicted within the modified three resonance (ω(783), φ(1020), φ′(1680)) vector-meson dominance (VMD) model with correct analytic properties and the asymptotic behaviour predestinated by the quark model for baryons. The resonance couplings to Λ are evaluated from the known couplings to nucleons by utilizing theSU(3) symmetry and normalization conditions for Dirac and Pauli form factors. The masses and widths of the considered vector mesons are fixed at the world averaged values. The optimal position of the effective inelastic threshold, common for Dirac and Pauli form factors, is determined from the fit of the only existing Orsay DM2 point on the\(e^ + e^ - \to \Lambda \bar \Lambda \) cross section att=5·693 GeV2. The mean square charge and magnetic radii of the Λ-hyperon are found to be 〈r E 2 〉Λ=0·018 F2 and 〈r M 2 〉Λ=−0·027 F2, respectively.