Soft charge form factor of the pion

Abstract

We identify the source of a discrepancy between $F_{\pi }^{\mathrm{soft}}|\mathrm{long}$ and $F_{\pi }^{\mathrm{soft}}|\mathrm{trans}$ found by Isgur and Llewellyn Smith. We find that the discrepancy disappears when virtual $q\overline{q}$ pair production for longitudinal-momentum transfers is included. Our result rectifies the discussion by Isgur and Llewellyn Smith of soft nonperturbative effects at presently available values of $Q^2$.