Quarkonia collectivity in large collision systems with ALICE

TL;DR

This paper presents ALICE Run 3 measurements of quarkonium elliptic flow at forward rapidity in Pb–Pb collisions, focusing on inclusive $J/\psi$ and $\Upsilon(1S)$ via three flow-analysis methods to access $v_{2}$ and its fluctuations. The results indicate a rising $v_{2}$ for $J/\psi$ from low to intermediate $p_{T}$—consistent with charm-quark thermalization and regeneration—while high-$p_{T}$ behavior reflects path-length dependent energy loss and hydrodynamic effects; cumulant measurements reveal small flow fluctuations. In contrast, $\Upsilon(1S)$ shows no significant $v_{2}$ signal within current uncertainties, and model comparisons begin to discriminate between regeneration and dissociation scenarios. Overall, Run 3 data provide improved precision and binning, helping to constrain heavy-quark dynamics in the QGP and the balance between suppression and regeneration in large collision systems.

Abstract

Quarkonium production is one of the golden probes to study the quark--gluon plasma (QGP). Among many observables, the measurement of azimuthal anisotropies in quarkonium production sheds light on the collective behavior of heavy-flavor particles in a strongly interacting medium. In particular, the measurements of the elliptic flow ($v_{2}$) of quarkonia in Pb--Pb collisions at the LHC provide us direct evidence of heavy quark thermalization in the QGP. In these proceedings, new results of inclusive $\mathrm{J/ψ}$ elliptic flow measurement in Pb--Pb collisions carried out by the ALICE collaboration in Run 3 using three methods including event-plane, scalar-product and multi-particle correlation (cumulant) will be presented. The method of cumulant will give access to the $\mathrm{J/ψ}$ flow fluctuations at forward rapidity. Alongside the new flow measurements of $\mathrm{J/ψ}$, new results of $\mathrmΥ(1S)$ flow measurement at forward rapidity in ALICE Run 3 will be presented as well with comparison to model calculations.

Figures (4)

• Figure 1: Inclusive $\mathrm{J/\psi}$$v_{2}$ at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36$ TeV as a function of $p_{\mathrm{T}}$. Left: in centrality intervals (0--10%, 10--30%, 30--50%) using the scalar-product method. Right: in centrality intervals (10--30%, 30--50%, 50--80%) using the event-plane method.
• Figure 2: Inclusive $\mathrm{J/\psi}$$v_{2}$ at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36$ TeV as a function of centrality in different $p_{\mathrm{T}}$ intervals (0--5 GeV/$c$, 5--20 (15) GeV/$c$). Left: the scalar-product method. Right: the event-plane method.
• Figure 3: Left: inclusive $\mathrm{J/\psi}$$v_{2}$ at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36$ TeV as a function of $p_{\mathrm{T}}$ within 10--30% centrality using the method of cumulant compared to event-plane, scalar product methods, and to the Run 2 results 12. Right: the $\mathrm{J/\psi}$ flow fluctuation at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36$ TeV as a function of $p_{\mathrm{T}}$ within 10--30% centrality compared to the CMS measurements of light-flavor particles 13.
• Figure 4: Inclusive $\mathrm{\Upsilon}(1S)$$v_{2}$ at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36$ TeV. Left: $p_{\mathrm{T}}$-integrated results within different centrality intervals compared to the Run 2 results 14. Right: results as a function of $p_{\mathrm{T}}$ within 5--60% centrality compared to calculations from TAMU 15 and BBJS 16 models.