Ruprecht Karls Universität Heidelberg

QCD, Strings and Particle Phenomenology

Topics Members Teaching

  • QCD under extreme conditions

Title    C. Ewerz

QCD Jets in the Quark Gluon Plasma    H.J. Pirner

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.

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