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. p. 136146.

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Abstract

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<y<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<pT<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.

Item Type: Article
Uncontrolled Keywords: 5106 Nuclear and Plasma Physics, 5107 Particle and High Energy Physics, 51 Physical Sciences
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 14 Dec 2021 16:55
Last Modified: 20 Jun 2024 18:52
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