Su(3)-breaking mechanisms for pseudoscalar-meson charge radii

The sum rule r+2-rK+2=nrK02 for pseudoscalar-meson charge radii is discussed. Working at the one-loop or quark-triangle approximation and assuming moderate SU(3) breaking for the constituent quark masses, one obtains n=-52. Experimental data are compatible with this value, but contradict the value n=-1 coming from vector-meson-dominance or U-spin symmetry-breaking mechanisms. © 1981 The American Physical Society.