  We have conducted a comprehensive angle-resolved photoemission study on the
normal state electronic structure of the Fe-based superconductor
Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$. We have identified four dispersive bands which
cross the Fermi level and form two hole-like Fermi surfaces around $\Gamma$ and
two electron-like Fermi surfaces around M. There are two nearly nested Fermi
surface pockets connected by an antiferromagnetic ($\pi$, $\pi$) wavevector.
The observed Fermi surfaces show small $k_z$ dispersion and a total volume
consistent with Luttinger theorem. Compared to band structure calculations, the
overall bandwidth is reduced by a factor of 2. However, many low energy
dispersions display stronger mass renormalization by a factor of $\sim$ 4,
indicating possible orbital (energy) dependent correlation effects. Using an
effective tight banding model, we fitted the band structure and the Fermi
surfaces to obtain band parameters reliable for theoretical modeling and
calculations of the important physical quantities, such as the specific heat
coefficient.
