Jet Quenching at LHC: ALICE weighs in

Yesterday, the ALICE Collaboration weighed in with a jet quenching result of their own. In their preprint

the ALICE physicists analyze a quantity much more familiar from the RHIC experiments: the suppression of large-pT hadrons in nuclear collisions relative to binary collision scaled p+p reactions. Three aspects are remarkable:

  1. The maximal suppression factor (1/RAA ≈ 7) at pT = 7 GeV is about 40% stronger than that seen at RHIC;
  2. RAA rises strongly with increasing pT, reaching 0.35 at 20 GeV;
  3. The shape of RAA(pT) in the intermediate range 1 GeV ≤ pT ≤ 7 GeV is almost identical to that observed at RHIC.
  4. The lower minimum of RAA in spite the much flatter slope of the hadron spectrum indicates a much larger energy loss of the leading parton. It will be interesting to see whether the energy loss coefficient scales like the charged particle multiplicity between RHIC and LHC.

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