  We present reliable many-body calculations for the t-t'-t''-U Hubbard model
that explain in detail the results of recent angle-resolved photoemission
experiments on electron-doped high-temperature superconductors. The origin of
the pseudogap is traced to two-dimensional antiferromagnetic spin fluctuations
whose calculated temperature dependent correlation length also agrees with
recent neutron scattering measurements. We make specific predictions for
photoemission, for neutron scattering and for the phase diagram.
