Hayrapetyan, A.Tumasyan, A.Adam, W.Andrejkovic, J. W.Benato, L.Bergauer, T.Druzhkin, D.2026-01-152026-01-1520250031-90071079-711410.1103/6ywq-gm612-s2.0-105018527440https://doi.org/10.1103/6ywq-gm61https://hdl.handle.net/20.500.14517/8695Noll, Dennis Daniel Nick/0000-0002-0176-2360; Pfeffer, Emanuel/0009-0009-1748-974X; Cavallari, Francesca/0000-0002-1061-3877; Mantilla, Cristina/0000-0002-0177-5903; Kasemann, Matthias/0000-0002-0429-2448; Jabeen, Shabnam/0000-0002-0155-7383; Goldouzian, Reza/0000-0002-0295-249X; Robertshaw, Liam/0009-0006-5304-2492; Petković, Ano/0009-0005-9565-6399; Dogra, Sunil Manohar/0000-0002-0812-0758; Kanuganti, Ankush Reddy/0000-0002-0789-1200; Govoni, Pietro/0000-0002-0227-1301; Menezes De Oliveira, Thales/0009-0009-4729-8354; Lee, Jason/0000-0002-2153-1519; Lintuluoto, Adelina/0000-0002-0726-1452; Lee, Jason/0000-0002-2153-1519; Castilla-Valdez, Heriberto/0009-0005-9590-9958; Cavallari, Francesca/0000-0002-1061-3877; Knight, Charlotte Rose/0009-0008-1167-4816; Qin, Xuelong/0009-0007-5089-3694; Riti, Federica/0000-0002-1466-9077; Cavallari, Francesca/0000-0002-1061-3877; Mantilla, Cristina/0000-0002-0177-5903; Lee, Jason/0000-0002-2153-1519; Matorras-Cuevas, Pablo/0000-0001-7481-7273; Ligabue, Franco/0000-0002-1549-7107; Heikkilä, Jaana/0000-0002-0538-1469; Chitroda, Bhakti/0000-0002-0220-8441;The polarization of the Lambda and (Lambda) over bar hyperons along the beam direction has been measured in proton-lead (p-Pb) collisions at a center-of-mass energy per nucleon pair of 8.16 TeV. The data were obtained with the CMS detector at the LHC and correspond to an integrated luminosity of 186.0 +/- 6.5 nb(-1). A significant azimuthal dependence of the hyperon polarization, characterized by the second-order Fourier sine coefficient P-z,P-s2, is observed. The P-z,P-s2 values decrease as a function of charged particle multiplicity, but increase with transverse momentum. A hydrodynamic model that describes the observed P-z,P-s2 values in nucleus-nucleus collisions by introducing vorticity effects does not reproduce either the sign or the magnitude of the p-Pb results. These observations pose a challenge to the current theoretical implementation of spin polarization in heavy ion collisions and offer new insights into the origin of spin polarization in hadronic collisions at LHC energies.eninfo:eu-repo/semantics/openAccessArticleQ1Q113513WOS:00160677060000141076707