  Nearby electron/positron accelerators, mostly Pulsar Wind Nebulae (PWNe),
have been proposed as potential origins of the positron excess above 10 GeV.
The HAWC Observatory reveals two very extended sources spatially coincident
with two nearby middle-aged pulsars: Geminga and PSR B0656+14, suggesting
ultrarelativistic electrons/positrons accelerated in our backyard.
Morphological studies on these two PWNe provide a constraint on the diffusion
coefficient at HAWC energies. In this poster, we will present the model
development and morphological studies on these PWNe, and the derived diffusion
coefficient that best fits the data.
