High $Q^2$ Probe of Nuclear Spectral Function and Color Transparency

Abstract

Contrary to widespread opinion, color transparency (CT) brings essential ambiguity to, rather than helps in, study of the nuclear spectral function in quasielastic lepton scattering, $A(l,l'p)A'$, at high $Q^2$. Although the nuclear attenuation vanishes, the final state interaction (FSI) of a small-size ejectile wave packet, propagating through nuclear matter, remains. It manifests itself in a substantial, but uncertain, longitudinal momentum transfer to the nuclear medium. We predict a strong Fermi-momentum bias of the nuclear transparency at high $Q^2$, which enters as a factor at the nuclear spectral function, and makes uncertain the results of measuring the high-momentum tail of Fermi distribution.