Pion charge radius from charged pion electroproduction - art. no. 028201

We analyze a low-energy theorem of threshold pion electroproduction which a llows one to determine the charge radius of the pion. We show that at the s ame order where the radius appears, pion loops induce a correction to the m omentum dependence of the longitudinal dipole amplitude L-0+((-)). This mod el-independent correction amounts to an increase of the pion charge radius squared from the electroproduction data by about 0.27 fm(2). It sheds light on the apparent discrepancy between the recent determination of the pion r adius from electroproduction data and the one based on pion-electron scatte ring.