  Jets are studied in A-A collisions at RHIC and LHC with the goal to
understand how they are affected by the medium and how they affect the medium.
It is widely believed that hard-scattered partons lose energy when propagating
through a medium before hadronizing. Partons losing enough energy may not even
make it out of the medium as identifiable jets (although the momentum will be
shared among whatever particles are emitted). "Full" jet reconstruction
attempts to determine the partonic energy loss as well as possible changes in
jet shape. Heavy ion collisions typically produce many unrelated particles
within the jet "cone," and subtraction of this background introduces
significant uncertainties. A variety of techniques using high-$p_t$ particles,
assumed to be leading particles from jet fragmentation, look for disappearance
of jets and attenuation of jets relative to the reaction plane, as well as
medium modifications such as Mach cones. Those techniques have considerable
uncertainty due to subtraction of $v_2$. In this paper we discuss minimum-bias
jets observed at RHIC using two-particle correlations. We find that jets
produced in p-p collisions have interesting properties. Peripheral A-A
collisions look like p-p collision. As we select more central collisions the
number of jets increases following binary collision scaling until at a
system-dependent centrality the number of particles associated with jets
increases substantially above this scaling. Near this transition centrality the
jet aspect ratio---elongated transverse to the beam direction for low-energy
jets produced in p-p collisions---becomes highly elongated along the beam
direction in A-A collisions.
