The quark-gluon plasma (QGP) is explored in
relativistic heavy ion collisions using the jet quenching signature,
i.e. the energy loss of a high energy quark or gluon as it traverses
the plasma. An exceptional energy loss sytematics in the data uncovers the
existence of the QGP. We develop a novel QCD evolution formalism in the
leading logarithm approximation, where normal parton radiation is
interleaved with scattering on the plasma gluons which take place at
a similar time scale. The idea has been elaborated in two models. One
is close to a Monte Carlo implementation extending the jet evolution
equations to fragmentation functions in the medium, facilitating the comparison of
phenomenologically useful numerical solutions with data.
The other approach includes the
dependence of the jet fragmentation function on transverse momentum,
allowing thereby a separation of the scales also for the scattering term.
With both methods,
the scatterings result in a characteristic softening of the jet
depending on the temperature of the plasma. In particular, leading
particles are substantially effected at RHIC and LHC energies.