Evidence of different prompt $\Lambda_c^+$ baryon and D meson elliptic flow in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.36 TeV with ALICE at the LHC

by Stefano Politano (CERN)

Tuesday 12 May 2026, 11:00 → 12:00 Europe/Zurich

500/1-001 - Main Auditorium (CERN)

 

According to QCD calculations on the lattice, at the high energy densities and temperatures reached in ultrarelativistic heavy-ion collisions, nuclear matter undergoes a phase transition to a colour-deconfined state, the quark-gluon plasma (QGP). Heavy quarks, charm and beauty, are produced early in the collision due to their large masses and thus experience the full evolution of the system, serving as excellent probes of QGP properties. As they traverse the expanding medium, heavy quarks interact with its constituents, losing energy and undergoing partial thermalisation. In a QGP, heavy quarks can hadronize via both fragmentation and recombination with lighter quarks from the medium. These mechanisms affect the properties of the observed final-state hadrons. In particular,  the azimuthal anisotropy, primarily quantified by the elliptic-flow coefficient (v2), of heavy-flavour hadrons in non-central collisions is particularly sensitive to the QGP transport coefficients, the heavy-quark degree of thermalisation in the medium, and the underlying hadronisation mechanism. The comparison of the $v_2$ of charm mesons and baryons gives direct insight into hadronisation mechanisms and the partonic origin of collective flow. Charm-baryon $v_2$ measurements remained absent from the experimental landscape until recently, limiting our understanding of heavy-quark hadronisation and QGP transport properties.

This seminar presents new measurements of charm-hadron $v_2$ in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.36$ TeV by the ALICE Collaboration. We report precision measurements of prompt non-strange and strange D-meson $v_2$, alongside the first experimental determination of the $\Lambda_c^+$ baryon $v_2$, spanning a wide range of transverse momentum. The results reveal differences between charm baryon and meson $v_2$ at medium-to-high transverse momentum, providing strong support to the partonic origin of collective flow in the heavy-flavour sector. The baryon-meson separation at high transverse momentum is consistent with a scenario where charm quarks combine with light quarks from the medium to form final-state hadrons. The measurements are compared with state-of-the-art transport-model predictions, providing new constraints on QGP transport properties.

 

Coffee will be served at 10h30