Fig. 2. Ratios of splitting angle probability distributions.

The ratios of the splitting-angle probability distributions for D⁰-meson tagged jets to inclusive jets, R(θ), measured in proton–proton collisions at $\sqrt{s}=13$ TeV, are shown for 5 < E_Radiator < 10 GeV (left panel), 10 < E_Radiator < 20 GeV (middle panel) and 20 < E_Radiator < 35 GeV (right panel). The data are compared with PYTHIA v.8 and SHERPA simulations, including the no dead-cone limit given by the ratio of the angular distributions for light-quark jets (LQ) to inclusive jets. The pink shaded areas correspond to the angles within which emissions are suppressed by the dead-cone effect, assuming a charm-quark mass of 1.275 GeV/c².