  We present a detailed analysis of broadband X-ray observations of the pulsar
PSR J1420-6048 and its wind nebula (PWN) in the Kookaburra region with Chandra,
XMM-Newton, and NuSTAR. Using the archival XMM-Newton and new NuSTAR data, we
detected 68 ms pulsations of the pulsar and characterized its X-ray pulse
profile which exhibits a sharp spike and a broad bump separated by ~0.5 in
phase. A high-resolution Chandra image revealed a complex morphology of the
PWN: a torus-jet structure, a few knots around the torus, one long (~7') and
two short tails extending in the northwest direction, and a bright diffuse
emission region to the south. Spatially integrated Chandra and NuSTAR spectra
of the PWN out to 2.5' are well described by a power law model with a photon
index ${\Gamma} {\approx}$ 2. A spatially resolved spectroscopic study, as well
as NuSTAR radial profiles of the 3--7 keV and 7--20 keV brightness, showed a
hint of spectral softening with increasing distance from the pulsar. A
multi-wavelength spectral energy distribution (SED) of the source was then
obtained by supplementing our X-ray measurements with published radio,
Fermi-LAT, and H.E.S.S. data. The SED and radial variations of the X-ray
spectrum were fit with a leptonic multi-zone emission model. Our detailed study
of the PWN may be suggestive of (1) particle transport dominated by advection,
(2) a low magnetic-field strength (B ~ 5${\mu}$G), and (3) electron
acceleration to ~PeV energies.
