Measurement of global polarization of Λ hyperons in few-GeV heavy-ion collisions
Creators: name: Yassine, R. Abou
name: Adamczewski-Musch, J.
name: Asal, C.
name: Becker, M.
name: Belounnas, A.
name: Blanco, A.
name: Blume, C.
name: Chlad, L.
name: Chudoba, P.
name: Ciepal, I.
name: Cordts, M.
name: Dreyer, J.
name: Esmail, W. A.
name: Fabbietti, L.
name: Floersheimer, H.
name: Fonte, P.
name: Friese, J.
name: Fröhlich, I.
name: Förtsch, J.
name: Galatyuk, T.
name: Gniazdowski, T
name: Greifenhagen, R.
name: Grunwald, M.
name: Gumberidze, M.
name: Harabasz, S.
name: Heinz, T.
name: Höhne, C.
name: Hojeij, F.
name: Holzmann, R.
name: Huck, H.
name: Idzik, M.
name: Kämpfer, B.
name: Kampert, K-H.
name: Kardan, B.
name: Kedych, V.
name: Koenig, I.
name: Koenig, W.
name: Kohls, M.
name: Kolas, J.
name: Kornakov, G.
name: Kotte, R.
name: Kres, I.
name: Krueger, W.
name: Kugler, A.
name: Lalik, R.
name: Lebedev, S.
name: Linev, S.
name: Linz, F.
name: Lopes, L.
name: Lorenz, M.
name: Malige, A.
name: Markert, J.
name: Matulewicz, T.
name: Maurus, S.
name: Metag, V.
name: Michel, J.
name: Molenda, A.
name: Müntz, C.
name: Nabroth, M.
name: Naumann, L.
name: Nowakowski, K.
name: Orliński, J.
name: Otto, J. -H.
name: Parschau, M.
name: Pauly, C.
name: Pechenov, V.
name: Pechenova, O.
name: Pfeifer, D.
name: Piasecki, K.
name: Pietraszko, J.
name: Povar, T.
name: Prozorov, A.
name: Przygoda, W.
name: Pysz, K.
name: Ramstein, B.
name: Rathod, N.
name: Ritman, J.
name: Rodriguez-Ramos, P.
name: Rost, A.
name: Rustamov, A.
name: Salabura, P.
name: Saraiva, J.
name: Schild, N.
name: Schwab, E.
name: Scozzi, F.
name: Seck, F.
name: Selyuzhenkov, I.
name: Singh, U.
name: Skorpil, L.
name: Smyrski, J.
name: Spies, S.
name: Stefaniak, M. S.
name: Ströbele, H.
name: Stroth, J.
name: Sumara, K.
name: Svoboda, O.
name: Szala, M.
name: Tlusty, P.
name: Traxler, M.
name: Wagner, V.
name: Wasiluk, M.
name: Weber, A. A.
name: Wendisch, C.
name: Wirth, J.
name: Zbroszczyk, H. P.
name: Zherebtsova, E.
name: Zielinski, M.
name: Zumbruch, P.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The global polarization of Λ hyperons along the total orbital angular momentum of a relativistic heavy-ion collision is presented based on the high statistics data samples collected in Au+Au collisions at \sqrt{s_{NN}} = 2.4 GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at GSI, Darmstadt. This is the first measurement below the strangeness production threshold in nucleon-nucleon collisions. Results are reported as a function of the collision centrality as well as a function of the hyperon transverse momentum (p_T) and rapidity (y_{CM}) for the range of centrality 0--40%. We observe a strong centrality dependence of the polarization with an increasing signal towards peripheral collisions. For mid-central (20--40%) collisions the polarization magnitudes are (%) = 6.8 \pm 1.3 (stat.) \pm 2.1 (syst.) for Au+Au and (%) = 6.2 \pm 0.4 (stat.) \pm 0.6 (syst.) for Ag+Ag, which are the largest values observed so far. This observation thus provides a continuation of the increasing trend previously observed by STAR and contrasts expectations from recent theoretical calculations predicting a maximum in the region of collision energies about 3 GeV. The observed polarization is of a similar magnitude as predicted by 3D fluid dynamics and the UrQMD plus thermal vorticity model and significantly above results from the AMPT model.
description: 8 pages, 4 figures