[Brahms-l] Fwd: New PHENIX paper on photon-hadron jet correlations in p+p and Au+Au

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> Title: Photon-Hadron Jet Correlations in p+p and Au+Au
> Collisions at sqrt s_NN=200 GeV
>
> Abstract:
> We report the observation at RHIC of suppression of back-to-back
> correlations in the direct photon+jet channel in Au+Au relative to
> p+p collisions. Two-particle correlations of direct photon triggers
> with associated hadrons are obtained by statistical subtraction of
> the decay photon-hadron background. The initial momentum of the
> away-side parton is tightly constrained since the parton-photon pair
> exactly balance in momentum at leading order in pQCD, making such
> correlations a powerful probe of the in-medium parton energy loss.
> The away-side nuclear suppression factor, IAA, in central Au+Au
> collisions, is 0:32 +/- 0:12(stat) +/- 0:09(sys)  for hadrons with
> pT = 3 – 5 GeV/c in coincidence with photons at pT = 5 - 15 GeV/c.
> The suppression is comparable to that observed for high-pT single
> hadrons and di-hadrons. The direct photon associated yields in p+p
> collisions scale approximately with the momentum balance,
> zT (pT hadron/ pT photon), as expected for a measure of the away-side
> parton fragmentation function. We compare to Au+Au collisions, in
> which the momentum balance dependence of the nuclear modification
> should be sensitive to the path-length dependence of parton energy  
> loss.

Flemming videbaek
videbaek @ bnl.gov
Brookhaven National Lab
631-344-4106
cell: 631-681-1596



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