Observation of Shadowing in the Virtual-Photon Total Hadronic Cross Section on Nuclei

Abstract

We have measured the total hadronic cross section of virtual photons incident on carbon, copper, and lead in the region ${Q}^{2}=0.01\ensuremath{-}30$ Ge${\mathrm{V}}^{2}$ and $\ensuremath{\nu}=40\ensuremath{-}200$ GeV. A 209-GeV/c muon beam was used as a source of virtual photons. The results indicate shadowing of the virtual photons below ${Q}^{2}=1$ Ge${\mathrm{V}}^{2}$ and a decrease of shadowing for ${Q}^{2}>3$ Ge${\mathrm{V}}^{2}$. The shadowing persists to larger ${Q}^{2}$ than indicated by experiments at lower $\ensuremath{\nu}$.