  A neutron or proton excess in nuclei leads to an isovector-vector mean-field
which, through its coupling to the quarks in a bound nucleon, implies a shift
in the quark distributions with respect to the Bjorken scaling variable. We
show that this result leads to an additional correction to the NuTeV
measurement of sin^2(Theta_W). The sign of this correction is largely model
independent and acts to reduce their result. Explicit calculation within a
covariant and confining Nambu--Jona-Lasinio model predicts that this vector
field correction accounts for approximately two-thirds of the NuTeV anomaly. We
are therefore led to offer a new interpretation of the NuTeV measurement,
namely, that it is further evidence for the medium modification of the bound
nucleon wavefunction.
