Supplemental Material: Measurements of the groomed jet radius and groomed momentum fraction in pp and Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV

This note presents jet substructure measurements in pp and Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV with the ALICE detector. The Soft Drop grooming algorithm provides access to the hard parton splittings inside a jet by removing soft wide-angle radiation. We report the groomed jet momentum fraction, $z_\rm{g}$, and the (scaled) groomed jet radius, $\theta_\rm{g} \equiv R_\rm{g}/R$. Charged-particle jets are reconstructed at midrapidity using the anti-$k_\rm{T}$ algorithm with resolution parameters $R=0.2$ and $R=0.4$. In heavy-ion collisions, the large underlying event poses a challenge for the reconstruction of groomed jet observables, since fluctuations in the background can cause groomed parton splittings to be misidentified. By using strong grooming conditions to reduce this background, we report these observables fully corrected for detector effects and background fluctuations for the first time. A narrowing of the $\theta_\rm{g}$ ($R_{\rm{g}}$) distribution in Pb-Pb collisions compared to pp collisions is observed, which provides direct evidence of the modification of the angular scale of jets in the quark-gluon plasma. No significant modification of the $z_\rm{g}$ distribution in Pb-Pb collisions compared to pp collisions is seen. These results are compared to a variety of theoretical models of jet quenching, and provide constraints on jet energy-loss mechanisms and coherence effects in the quark-gluon plasma.