Van der Steenhoven et al. reply.

Abstract

The Comment by Lourie and Ulmer on our recent Letter asks for further clarification of our arguments and conclusions. The authors of the Comment correctly state that a modification of the electron-proton coupling, that is identical for the longitudinal (${\mathit{W}}_{\mathit{L}}$) and transverse (${\mathit{W}}_{\mathit{T}}$) response functions, would go unnoticed in the ratio of reduced cross sections R. However, the experimental observation that R\ensuremath{\ne}1 does imply that the e-p coupling is different in the nuclear environment. Moreover, it implies that the longitudinal and transverse response functions are affected in a different way, invalidating their assumption of equal modifications. We recall that it it was the purpose of the $^{6}\mathrm{Li}$(e,e'p) experiment.