EPJ Featured Talk: First direct measurement of radial flow in heavy-ion collisions with ALICE

This work presents measurements of the transverse-momentum-dependent observable $v_0(p_{\mathrm{T}})$ as a novel probe of radial expansion dynamics in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=5.02$ TeV with the ALICE detector. Results are reported for inclusive charged hadrons, pions, kaons, and protons across centrality intervals, using a pseudorapidity gap to suppress short-range nonflow correlations. At low $p_{\mathrm{T}}$, a clear mass ordering is observed, consistent with hydrodynamic expectations. For $p_{\mathrm{T}}>3$ GeV/$c$, protons exhibit larger $v_0(p_{\mathrm{T}})$ than pions and kaons, in line with quark recombination models. These results demonstrate the sensitivity of $v_0(p_{\mathrm{T}})$ to collective expansion and hadronization dynamics in the quark–gluon plasma.