Jet cone size dependence of single inclusive jet suppression due to jet quenching in Pb + Pb collisions at s N N = 5.02 TeV

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 A A ) and their double ratios R A A ( R = 0.2 – 1.0 ) / R A A ( R = 0.2 ) , and systematically compare with ALICE, ATLAS, and CMS data in 0–10% and 30–50% Pb + Pb collisions at s N N = 5.02 TeV . Numerical results show that R A A 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 A A double ratios are approximately unity for small radii ( R = 0.4 relative to R = 0.2 ) and at high p T ≳ 200 GeV / c , in agreement with the data within uncertainties.