  We demonstrate that jet observables are highly sensitive to the
characteristics of the vacuum and the in-medium QCD parton showers and propose
techniques that exploit this sensitivity to constrain the mechanism of quark
and gluon energy loss in strongly-interacting plasmas. As a first example, we
calculate the inclusive jet cross section in high-energy nucleus-nucleus
collisions to ${\cal O}(\alpha_s^3)$. Theoretical predictions for the
medium-induced jet broadening and the suppression of the jet production rate
due to cold and hot nuclear matter effects in Au+Au and Cu+Cu reactions at RHIC
are presented.

High Energy Physics - Phenomenology;Nuclear Theory