학술논문
Measurement of global polarization of {\Lambda} hyperons in few-GeV heavy-ion collisions
Document Type
Working Paper
Author
Yassine, R. Abou; Adamczewski-Musch, J.; Asal, C.; Becker, M.; Belounnas, A.; Blanco, A.; Blume, C.; Chlad, L.; Chudoba, P.; Ciepal, I.; Cordts, M.; Dreyer, J.; Esmail, W. A.; Fabbietti, L.; Floersheimer, H.; Fonte, P.; Friese, J.; Fröhlich, I.; Förtsch, J.; Galatyuk, T.; Gniazdowski, T; Greifenhagen, R.; Grunwald, M.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Höhne, C.; Hojeij, F.; Holzmann, R.; Huck, H.; Idzik, M.; Kämpfer, B.; Kampert, K-H.; Kardan, B.; Kedych, V.; Koenig, I.; Koenig, W.; Kohls, M.; Kolas, J.; Kornakov, G.; Kotte, R.; Kres, I.; Krueger, W.; Kugler, A.; Lalik, R.; Lebedev, S.; Linev, S.; Linz, F.; Lopes, L.; Lorenz, M.; Malige, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Molenda, A.; Müntz, C.; Nabroth, M.; Naumann, L.; Nowakowski, K.; Orliński, J.; Otto, J. -H.; Parschau, M.; Pauly, C.; Pechenov, V.; Pechenova, O.; Pfeifer, D.; Piasecki, K.; Pietraszko, J.; Povar, T.; Prozorov, A.; Przygoda, W.; Pysz, K.; Ramstein, B.; Rathod, N.; Ritman, J.; Rodriguez-Ramos, P.; Rost, A.; Rustamov, A.; Salabura, P.; Saraiva, J.; Schild, N.; Schwab, E.; Scozzi, F.; Seck, F.; Selyuzhenkov, I.; Singh, U.; Skorpil, L.; Smyrski, J.; Spies, S.; Stefaniak, M. S.; Ströbele, H.; Stroth, J.; Sumara, K.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Wagner, V.; Wasiluk, M.; Weber, A. A.; Wendisch, C.; Wirth, J.; Zbroszczyk, H. P.; Zherebtsova, E.; Zielinski, M.; Zumbruch, P.
Source
Physics Letters B, Volume 835, 10 December 2022, 137506
Subject
Language
Abstract
The global polarization of {\Lambda} 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.
Comment: 8 pages, 4 figures
Comment: 8 pages, 4 figures