Physical Review Letters 95,15 (2005) 152301;
Charged hadrons in 0.15 < p(perpendicular to)< 4 GeV/c associated with particles of p(perpendicular to)(trig)> 4 GeV/c are reconstructed in pp and Au+Au collisions at root s(NN)=200 GeV. The associated multiplicity and p(perpendicular to) magnitude sum are found to increase from pp to central Au+Au collisions. The associated p(perpendicular to) distributions, while similar in shape on the nearside, are significantly softened on the awayside in central Au+Au relative to pp and not much harder than that of inclusive hadrons. The results, consistent with jet quenching, suggest that the awayside fragments approach equilibration with the medium traversed.
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