Second-class currents and very light quarks

Abstract

We consider induced second-class nucleon currents in a light-quark model generated by unequal $u$ and $d$ quark masses. The effect produced by gluon vertex corrections is strikingly large without confinement effects. Restricting the quarks to the limited spatial region of a physical nucleon changes the energy scale from the quark mass to the quark-bound-state energy and thereby reduces the second-class form factors well below their first-class counterparts.