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

Abstract

The sum rule $〈{r_{{\pi }^{+}}}^2〉-〈{r_{K^{+}}}^2〉=n〈{r_{K0\mathrm{}}}^2〉$ 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 $n=-\frac{5}{2}$. Experimental data are compatible with this value, but contradict the value $n=-1\mathrm{}$ coming from vector-meson-dominance or $U$-spin symmetry-breaking mechanisms.