Jet-Hadron Correlations insNN=200  GeVp+p

Dijet imbalance measurements in Au+Au and pp collisions at sNN

“…By contrast, at RHIC energies, measurements based on correlations of hadrons with leading reconstructed jets or non-decay (direct) photons indicate that the lost energy remains much closer to the jet axis [15,16], suggesting only a moderate broadening of the jet structure for all but the softest constituents. The difference between the RHIC and LHC energy results could be due to a number of different reasons; both the details of the experimental analyses and the mean parton kinematics being probed at the two facilities differ significantly.…”

“…The heavy ion background has the potential to bias an online high tower trigger toward a higher population of low-energy jets that would not be accounted for by the embedding. In a previous study, this effect was conservatively accounted for with a small systematic uncertainty [15]. The relatively high leading jet requirement and the robustness of the observable in this analysis further reduce a potential influence of such a bias.…”

“…In order to make meaningful quantitative comparisons between the di-jet imbalance measured in Au+Au to that in p + p, it is however necessary to compare jets which have similar initial parton energies in the two collision systems, and to take the remaining effect of background fluctuations into account. It was shown in [15] that Au+Au HT leading jets are similar to p + p HT leading jets embedded in a Au+Au background. A di-jet imbalance reference dataset is therefore constructed in this analysis via embedding p + p HT events into Au+Au minimum bias (i. e., without a high tower trigger) events with a 0-20% centrality requirement identical to the HT data (p + p HT ⊕ Au+Au MB).…”

“…The relative TPC tracking efficiency in Au+Au is ca. 90% ± 7% that of p + p [15], and this difference is accounted for in the p + p HT ⊕ Au+Au MB during embedding by randomly rejecting charged p + p tracks with a probability given by this efficiency difference. The uncertainty on this correction is the largest contributor to systematic uncertainty, and it is assessed by repeating the measurement with the respective minimum and maximum efficiency.…”

Event-plane-dependent dihadron correlations with harmonicvnsubtraction in Au + Au collisions atsNN=200GeV

“…Deflection of correlated particles may have already been seen in three-particle correlations [35] where the diagonal peak is stronger than the off-diagonal peak whereas the unsubtracted v 3 (and possible Mach-cone emission) should yield the same strength for those peaks. However, in jet-hadron correlations where the trigger jet has significantly larger energy than the trigger particle in this analysis, no deflection of associated particles is observed [36].…”