(Under construction)

There are two main strategies to explore any physical phenomenon: The passive approach is to extract as much information as possible from measurables provided by the system itself. Examples for the case of the Quark Gluon Plasma (QGP) created at RHIC include spectra of "normal" or "exotic" particles in the medium, as well as collective behavior such as temperature or hydrodynamic flow.

The active approach on the other hand studies the reaction to an external probe. Requirements for such a probe of the QGP are lofty: It needs to be sensitive to the strong force, i.e. either a quark or a gluon, both of which only exist bound inside a nucleon or in the QGP itself. It needs to be available during the exceedingly small lifetime (less than 10^-22 seconds) of the medium after a heavy ion collision, and it needs to be of sufficiently high energy to probe deeply. Serendipitously, such probes do not only exist but they come complimentary in many collisions: Jets.