Speaker
Description
The transverse momentum dependent observable $v_{0}(p_\mathrm{T})$ has recently emerged as a novel probe of radial expansion in high-energy heavy-ion collisions. Using Pb$-$Pb collision data at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV recorded with the ALICE detector, measurements of $v_{0}(p_\mathrm{T})$ for pions, kaons, and protons are performed across a broad range of collision centralities. A pseudorapidity gap technique is employed to suppress short-range nonflow correlations and isolate collective dynamics. The results reveal clear mass ordering at low $p_{T}$ and baryon-meson separation at higher $p_\mathrm{T}$, reflecting hydrodynamic expansion and hadronization via quark recombination. Comparative modeling with a blast-wave framework, including event-by-event fluctuations of radial flow velocity and freeze-out temperature, shows consistency with parameters extracted from transverse momentum spectra. Moreover, the sensitivity of $v_{0}(p_\mathrm{T})$ to bulk-viscosity effects and the underlying equation of state highlights its potential as a complementary observable for constraining the transport properties and freeze-out dynamics of the quark$-$gluon plasma.
