  We study high-pt jets from QCD and from highly-boosted massive particles such
as tops, W, Z and Higgs, and argue that infrared-safe observables can help
reduce QCD backgrounds. Jets from QCD are characterized by different patterns
of energy flow compared to the products of highly-boosted heavy particle
decays, and we employ a variety of jet shapes, observables restricted to energy
flow within a jet, to explore this difference. Results from Monte Carlo
generators and arguments based on perturbation theory support the
discriminating power of the shapes we refer to as planar flow and angularities.
We emphasize that for massive jets, these and other observables can be analyzed
perturbatively.
