A1 Journal article (refereed)
First measurement of quarkonium polarization in nuclear collisions at the LHC (2021)

ALICE Collaboration. (2021). First measurement of quarkonium polarization in nuclear collisions at the LHC. Physics Letters B, 815, Article 136146. https://doi.org/10.1016/j.physletb.2021.136146

JYU authors or editors

Publication details

All authors or editorsALICE Collaboration

Journal or seriesPhysics Letters B



Publication year2021


Article number136146


Publication countryNetherlands

Publication languageEnglish


Publication open accessOpenly available

Publication channel open accessOpen Access channel

Publication is parallel published (JYX)https://jyx.jyu.fi/handle/123456789/74676

Web address of parallel published publication (pre-print)https://arxiv.org/abs/2005.11128


The polarization of inclusive J/ψ and ϒ(1S) produced in Pb–Pb collisions at sNN=5.02 TeV at the LHC is measured with the ALICE detector. The study is carried out by reconstructing the quarkonium through its decay to muon pairs in the rapidity region 2.5<4 and measuring the polar and azimuthal angular distributions of the muons. The polarization parameters λθ, λϕ and λθϕ are measured in the helicity and Collins-Soper reference frames, in the transverse momentum interval 2<10 GeV/c and pT<15 GeV/c for the J/ψ and ϒ(1S), respectively. The polarization parameters for the J/ψ are found to be compatible with zero, within a maximum of about two standard deviations at low pT, for both reference frames and over the whole pT range. The values are compared with the corresponding results obtained for pp collisions at s=7 and 8 TeV in a similar kinematic region by the ALICE and LHCb experiments. Although with much larger uncertainties, the polarization parameters for ϒ(1S) production in Pb–Pb collisions are also consistent with zero.

Keywordsparticle physicspolarisation

Contributing organizations

Ministry reportingYes

Reporting Year2021

JUFO rating2

Last updated on 2024-22-04 at 20:58