Measurement of $π^0$-hadron correlations relative to the event plane in semicentral Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV

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Main Author: ALICE Collaboration
Format: Preprint
Published: 2026
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author ALICE Collaboration
author_facet ALICE Collaboration
contents Per-trigger yields of $π^0$-hadron correlations were measured in semicentral Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV in ALICE at the LHC. The reconstructed $π^0 \rightarrow γγ$, with a transverse momentum of $11 < p_{\rm T}(π^0) < 14$ 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 $2^{\rm nd}$-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 $p_{\rm T} \approx 2$ GeV/$c$ when comparing out-of-plane to in-plane trigger particles. At associated charged-particle $p_{\rm T} > 3$ 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.
format Preprint
id arxiv_https___arxiv_org_abs_2602_22866
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Measurement of $π^0$-hadron correlations relative to the event plane in semicentral Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV
ALICE Collaboration
Nuclear Experiment
Per-trigger yields of $π^0$-hadron correlations were measured in semicentral Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV in ALICE at the LHC. The reconstructed $π^0 \rightarrow γγ$, with a transverse momentum of $11 < p_{\rm T}(π^0) < 14$ 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 $2^{\rm nd}$-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 $p_{\rm T} \approx 2$ GeV/$c$ when comparing out-of-plane to in-plane trigger particles. At associated charged-particle $p_{\rm T} > 3$ 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.
title Measurement of $π^0$-hadron correlations relative to the event plane in semicentral Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV
topic Nuclear Experiment
url https://arxiv.org/abs/2602.22866