Speaker
Description
The observation of long-range correlations is a crucial indicator of collectivity in heavy-ion collisions and has been instrumental in establishing the formation of quark-gluon plasma (QGP) at RHIC and LHC. In this study, the first direct measurement of radial flow is presented using a new observable, $ v_{\rm 0}(p_{\rm T}) $, formulated to capture the long-range correlations in the transverse momentum $ p_{\rm T} $ spectrum. Unlike anisotropic flow coefficients $ v_{\rm n}(p_{\rm T}) $, which are influenced by both shear and bulk viscosity, $v_{\rm 0}(p_{\rm T}) $ is sensitive solely to the bulk properties of the QGP medium, making it a valuable probe for studying bulk viscosity and the hydrodynamic evolution of the system formed in heavy-ion collisions.
The measurement of $ v_{\rm 0}(p_{\rm T})$ is reported across various centrality classes for inclusive charged particles and identified particles, such as pions, kaons, and protons, in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector. To minimize short-range non-flow correlations, a rapidity gap technique similar to that used in anisotropic flow measurements is employed. At low $p_{\rm T}$, characteristic mass ordering, typically associated with collective flow in $v_{\rm n}(p_{\rm T})$, is observed. At higher $ p_{\rm T} $, where hydrodynamic descriptions fail, a baryon-meson splitting indicative of quark coalescence is observed. Measurements are compared with the hydrodynamic model MUSIC under varied initial conditions, as well as non-hydrodynamic models like HIJING and EPOS.
| Category | Experiment |
|---|---|
| Collaboration (if applicable) | ALICE |
