Measurement of π 0 -hadron correlations relative to the event plane in semicentral Pb-Pb collisions at s N N = 5.02 TeV

Per-trigger yields of π 0 − hadron correlations were measured in semicentral Pb-Pb collisions at s NN = 5.02 TeV in ALICE at the CERN Large Hadron Collider. The reconstructed π 0 → γ γ , with a transverse momentum of 11 GeV / c < p T ( π 0 ) < 14 GeV / c , is used as the trigger particle to calculate yields of associated charged particles on the near- and away-side. The photons are reconstructed using the ALICE Electromagnetic Calorimeter, and the charged particles are measured in the ALICE central barrel within a pseudorapidity range of | η | < 0.8 . The yields are reported relative to the orientation of the π 0 with the second-order event plane and are background subtracted using the reaction-plane fit method. The data give an indication of a suppression of the associated charged-particle yields near p T ≈ 2 GeV / c when comparing out-of-plane to in-plane trigger particles. At associated charged-particle p T > 3 GeV/ c , no significant event-plane dependence is observed within uncertainties. The results are compared with predictions from the JEWEL model, which implements jet energy loss in an expanding medium. JEWEL predicts no significant modification of either the near- or away-side associated yields, independent of whether medium recoils are included. The observed behavior may indicate the presence of additional energy-loss mechanisms beyond those governed by path-length dependence.