Deciphering yield modification of hadron-triggered semi-inclusive recoil jets in heavy-ion collisions

¹ Institute of Frontier and Interdisciplinary Science, Shandong University
² Key Laboratory of Particle Physics and Particle Irradiation, Ministry of Education, Shandong University
³ Physics Department, Brookhaven National Laboratory
⁴ Yale University

^* e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
^** Speaker. Current address: University of Science and Technology of China

Published online: 5 November 2025

Abstract

Jet quenching is recognized as critical evidence for the existence of the quark-gluon plasma (QGP) and serves as an essential probe to study its transport properties. Measurements of hadron-triggered semi-inclusive recoil jets have gained popularity due to its capability to probe jets over an extended phase space at low transverse momenta (p_T) and large radii. Recent ALICE measurements showed that the I_AA, yield ratio of recoil jets between heavy-ion and p+p collisions, rises with jet p_T and exceeds unity at high p_T, contradicting conventional expectations that jet quenching should result in I_AA values less than one. In this contribution, we re-examine the surface bias and study the effects of energy losses for both trigger hadrons and recoil jets on I_AA, employing the Linear Boltzmann Transport (LBT) model to simulate jet-medium interactions. Our findings suggest that a large portion of hadrons used for the triggers undergoes substantial energy loss, despite surface bias. In particular, the energy loss of the trigger hadrons elevates the I_AA baseline, corresponding to the case of no energy loss for recoil jets, to be greatly larger than unity. This enhancement of the baseline implies that the measured I_AA values being larger than unity could still signal jet quenching.