First measurement of quarkonium polarization in nuclear collisions at the LHC



Acharya, S, Adamova, D, Adler, A, Adolfsson, J, Aggarwal, MM, Rinella, G Aglieri, Agnello, M, Agrawal, N, Ahammed, Z, Ahmad, S
et al (show 1018 more authors) (2021) First measurement of quarkonium polarization in nuclear collisions at the LHC PHYSICS LETTERS B, 815. 136146-. ISSN 0370-2693, 1873-2445

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Abstract

The polarization of inclusive J/ψ and ϒ(1S) produced in Pb–Pb collisions at s<inf>NN</inf>=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<y<4 and measuring the polar and azimuthal angular distributions of the muons. The polarization parameters λ<inf>θ</inf>, λ<inf>ϕ</inf> and λ<inf>θϕ</inf> are measured in the helicity and Collins-Soper reference frames, in the transverse momentum interval 2<p<inf>T</inf><10 GeV/c and p<inf>T</inf><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 p<inf>T</inf>, for both reference frames and over the whole p<inf>T</inf> 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.

Item Type: Article
Uncontrolled Keywords: 5106 Nuclear and Plasma Physics, 5107 Particle and High Energy Physics, 51 Physical Sciences
Divisions: Faculty of Science & Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 14 Dec 2021 16:55
Last Modified: 16 Jun 2026 07:54
DOI: 10.1016/j.physletb.2021.136146
Open Access URL: https://www.sciencedirect.com/science/article/pii/...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3145364
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