Electroproduction of Single Pions with Large Transverse Momenta

Abstract

We report measurements of the electroproduction reaction $\mathrm{ep}\ensuremath{\rightarrow}e{\ensuremath{\pi}}^{+}n$ for pions produced between 60 and 90\ifmmode^\circ\else\textdegree\fi{} in the virtual-photon-proton center-of-mass system. The cross section is studied as a function of the center-of-mass energy, $W$, and the square of the virtual-photon mass, $\ensuremath{-}{Q}^{2}$, in the region $1.2 \mathrm{GeV}<~W<~3.0 \mathrm{GeV}$, $1.2 \mathrm{Ge}{\mathrm{V}}^{2}<~{Q}^{2}<~4.4 \mathrm{Ge}{\mathrm{V}}^{2}$. The data show a strong $W$ dependence in accord with simple quark-model predictions but exhibit a ${Q}^{2}$ dependence which is difficult to explain in the context of such a model.