  We present a broadband X-ray study of W50 (`the Manatee nebula'), the complex
region powered by the microquasar SS 433, that provides a test-bed for several
important astrophysical processes. The W50 nebula, a Galactic PeVatron
candidate, is classified as a supernova remnant but has an unusual double-lobed
morphology likely associated with the jets from SS 433. Using NuSTAR,
XMM-Newton, and Chandra observations of the inner eastern lobe of W50, we have
detected hard non-thermal X-ray emission up to $\sim$30 keV, originating from a
few-arcminute size knotty region (`Head') located $\lesssim$ 18$^{\prime}$ (29
pc for a distance of 5.5 kpc) east of SS 433, and constrain its photon index to
1.58$\pm$0.05 (0.5-30 keV band). The index gradually steepens eastward out to
the radio `ear' where thermal soft X-ray emission with a temperature
$kT$$\sim$0.2 keV dominates. The hard X-ray knots mark the location of
acceleration sites within the jet and require an equipartition magnetic field
of the order of $\gtrsim$12$\mu$G. The unusually hard spectral index from the
`Head' region challenges classical particle acceleration processes and points
to particle injection and re-acceleration in the sub-relativistic SS 433 jet,
as seen in blazars and pulsar wind nebulae.
