Speaker:  Qing-Fei Han (韩庆飞)
Time: 12 December (Friday) 2025, 2:00 pm
Location: 9409

Abstract:

Jet suppression in high-energy heavy-ion collisions results from jet energy loss and transverse-momentum broadening during jet propagation through the quark-gluon plasma (QGP). The jet cone size ($R$) dependence of this suppression offers crucial insights into the energy loss mechanisms and QGP transport properties. In our study, we implement a comprehensive approach within the perturbative QCD parton model that incorporates both elastic and inelastic energy loss mechanisms. For elastic processes the contribution from recoiling thermal partons reduces the net in-cone energy loss for a given jet radius. For inelastic processes, we account for the angular distribution of radiated gluons, the thermalization of soft gluons, and transverse-momentum broadening. Using this framework, we calculate the jet nuclear modification factors ($R_{AA}$) and their double ratios $R_{AA}(R=0.2-1.0)/R_{AA}(R=0.2)$, and systematically compare with ALICE, ATLAS and CMS data  in 0-10\% and 30-50\% Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02TeV. Numerical results show that $R_{AA}$ increases with the cone size $R$ because the in-cone energy loss decreases at larger radii.  Specifically, as the radius $R$ grows, the probability for elastically scattered partons to escape the jet cone and the likelihood for radiated gluons to fall outside the cone both decrease, resulting in a net reduction of energy loss. The $R_{AA}$ double ratios are approximately unity for small radii ($R=0.4$ relative to $R=0.2$) and at high $p_{T}\gtrsim200$ GeV$/c$, in agreement with the data within uncertainties.