Baryonic content of the pion

Abstract

The baryon form factor of charged pions arises since isospin symmetry is broken. We obtain estimates for this basic property in two phenomenological ways: from simple constituent quark models with unequal up and down quark masses, and from fitting to e+e−→π+π−data. All our methods yield a positive π+baryon mean square radius of (0.03 −0.04fm)2. Hence, a picture emerges where the outer region has a net baryon, and the inner region a net antibaryon density, both compensating each other such that the total baryon number is zero. For π−the effect is opposite.