Quarkonium polarization at the LHC energies with ALICE

Quarkonium polarization studies in hadronic collisions are robust tests for Quantum
Chromodynamics (QCD). Nonrelativistic QCD (NRQCD) can explain quarkonium production
reasonably well; however, it fails to predict measurements of quarkonium polarization. The
NRQCD calculations with dominant contributions from the color-octet component predict
transverse polarization of charmonia at high transverse momentum (𝑝𝑇) at the LHC energies.
On the other hand, the next-to-leading order (NLO) calculations of the color-singlet model
show a strong longitudinal polarization. These opposite theoretical predictions are not
supported by recent quarkonium polarization results released at the LHC energies, which tend
to favour zero or very small polarization scenarios. Additional quarkonium polarization
measurements, in particular for less abundantly produced states such as excited charmonia and
bottomonia, are therefore mandatory to better understand quarkonium production mechanisms,
both in proton-proton and nucleus-nucleus collisions. Considering heavy-ion collisions,
quarkonium polarization can also be used to investigate the characteristics of the hot and dense
medium created at the LHC energies. ALICE measures inclusive quarkonium production at
both mid-rapidity (|y| < 0.9) and forward rapidity (2.5 < y < 4.0) down to zero 𝑝𝑇. In this
contribution, we report on the recent ALICE results on Υ(1S) polarization and the status of
ongoing J/ψ, ψ(2S) polarization analyses at forward rapidity in pp collision at √𝑠 = 13 TeV. In
addition, the latest published result of J/ψ polarization in Pb-Pb collisions at √𝑠𝑁𝑁 = 5.02 TeV
will be presented.
In near future, studying quarkonia in ALICE 3 will be crucial. The Muon Identifier (MID) in
ALICE 3 is designed to efficiently identify muons by matching tracklets from its detector layers
with tracks from the inner tracker. It ensures high muon efficiency while providing strong
hadron rejection, which will enable precise measurements of quarkonium states via the dimuon
channel, even at low transverse momentum. This will helps us to probe the quark-gluon plasma
properties and understand heavy-quark interactions in extreme QCD conditions.