First measurement of quarkonium polarization in nuclear collisions at the LHC

0541978 - ÚJF 2022 RIV NL eng J - Journal Article
Acharya, S. - Adamová, Dagmar - Bielčík, J. - Bielčíková, Jana - Broz, M. - Contreras, J. G. - Herman, T. - Horák, D. - Isakov, Artem - Křížek, Filip - Křížková Gajdošová, K. - Kushpil, Svetlana - Lavička, R. - Mareš, Jiří A. - Petráček, V. - Šafařík, K. - Šumbera, Michal - Závada, Petr … Total 1007 authors
First measurement of quarkonium polarization in nuclear collisions at the LHC.
Physics Letters. B. Roč. 815, APR (2021), č. článku 136146. ISSN 0370-2693. E-ISSN 1873-2445
R&D Projects: GA MŠMT(CZ) LTT17018
Research Infrastructure: CERN-CZ II - 90104
Institutional support: RVO:68378271 ; RVO:61389005
Keywords : ALICE collaboration * heavy ion experiments * Pb-Pb collisions
OECD category: Nuclear physics; Particles and field physics (FZU-D)
Impact factor: 4.950, year: 2021
Method of publishing: Open access
https://doi.org/10.1016/j.physletb.2021.136146

The polarization of inclusive J/psi and Upsilon(1S) produced in Pb-Pb collisions at root s(NN) = 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 lambda(theta), lambda(phi) and lambda(theta phi) are measured in the helicity and Collins-Soper reference frames, in the transverse momentum interval 2 < p(T) < 10 GeV/c and p(T) < 15 GeV/c for the J/psi and Upsilon(1S), respectively. The polarization parameters for the J/psi are found to be compatible with zero, within a maximum of about two standard deviations at low p(T), for both reference frames and over the whole p(T) range. The values are compared with the corresponding results obtained for pp collisions at root 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 Upsilon(1S) production in Pb-Pb collisions are also consistent with zero.
Permanent Link: http://hdl.handle.net/11104/0319487