Observation of a Coherence Length Effect in Exclusive<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="italic">ρ</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>Electroproduction

Exclusive incoherent electroproduction of the ${\ensuremath{\rho}}^{0}\left(770\right)$ meson from ${}^{1}\mathrm{H}$, ${}^{2}\mathrm{H}$, ${}^{3}\mathrm{He}$, and ${}^{14}\mathrm{N}$ targets has been studied by the HERMES experiment at squared four-momentum transfer ${Q}^{2}&gt;0.4{\mathrm{GeV}}^{2}$ and positron energy loss $\ensuremath{\nu}$ from 9 to 20 GeV. The ratio of the ${}^{14}\mathrm{N}$ to ${}^{1}\mathrm{H}$ cross sections per nucleon, known as the nuclear transparency, was found to decrease with increasing coherence length of quark-antiquark fluctuations of the virtual photon. The data provide clear evidence of the interaction of the quark-antiquark fluctuations with the nuclear medium.