"QGP" effects: radiative parton energy loss

• Multiple final-state gluon radiation off the produced hard parton (before hadronization) induced by the traversed (dense and hot) colored medium:

  • Mean parton energy loss: DE ~ as ·CF ·rgluon(T)·DL2
  • Energy is carried away by gluon bremsstrahung
  • outside jet cone: dE/dx ~ as ák2Tñ
  • 2 basic formalisms ("thin" and "thick" plasmas):
  • - GLV: opacity L/l expansion
  • - BDMPS: gluon transport coeff. ~rgluon(T)
  • Expanding vs. static plasma:
  • DE1-D =(2t0/RA)DEstat ~15·DEstat (t0=0.2 fm/c, RA=6 fm)

• Observables:

• i) Depletion of leading-particle inclusive high pT

• spectra: "jet quenching"

• ii) Photon-tagged jets, direct g vs fragmentation g ...

• Well above energy loss in cold nuclear matter:

  • BDMPS: DE(T=250 MeV) ~ 15·DE(T=0)
  • X.N.Wang: dE/dx ~0.5 GeV/fm (HERMES eA data)
  • FNAL E772: dE/dx ~0.2 GeV/fm (D.Y. pA data)