Measurement of global polarization of Λ hyperons in few-GeV heavy-ion collisions

Autor: R. Abou Yassine, J. Adamczewski-Musch, C. Asal, M. Becker, A. Belounnas, A. Blanco, C. Blume, L. Chlad, P. Chudoba, I. Ciepał, M. Cordts, J. Dreyer, W.A. Esmail, L. Fabbietti, H. Floersheimer, P. Fonte, J. Friese, I. Fröhlich, J. Förtsch, T. Galatyuk, T. Gniazdowski, R. Greifenhagen, M. Grunwald, M. Gumberidze, S. Harabasz, T. Heinz, C. Höhne, F. Hojeij, R. Holzmann, H. Huck, M. Idzik, B. Kämpfer, K-H. Kampert, B. Kardan, V. Kedych, I. Koenig, W. Koenig, M. Kohls, J. Kolas, G. Kornakov, R. Kotte, I. Kres, W. Krueger, A. Kugler, R. Lalik, S. Lebedev, S. Linev, F. Linz, L. Lopes, M. Lorenz, A. Malige, J. Markert, T. Matulewicz, S. Maurus, V. Metag, J. Michel, A. Molenda, C. Müntz, M. Nabroth, L. Naumann, K. Nowakowski, J. Orliński, J.-H. Otto, M. Parschau, C. Pauly, V. Pechenov, O. Pechenova, D. Pfeifer, K. Piasecki, J. Pietraszko, T. Povar, A. Prozorov, W. Przygoda, K. Pysz, B. Ramstein, N. Rathod, J. Ritman, P. Rodriguez-Ramos, A. Rost, A. Rustamov, P. Salabura, J. Saraiva, N. Schild, E. Schwab, F. Scozzi, F. Seck, I. Selyuzhenkov, U. Singh, L. Skorpil, J. Smyrski, S. Spies, M.S. Stefaniak, H. Ströbele, J. Stroth, K. Sumara, O. Svoboda, M. Szala, P. Tlusty, M. Traxler, V. Wagner, M. Wasiluk, A.A. Weber, C. Wendisch, J. Wirth, H.P. Zbroszczyk, E. Zherebtsova, M. Zielinski, P. Zumbruch
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Zdroj: Physics Letters B, Vol 835, Iss , Pp 137506- (2022)
Druh dokumentu: article
ISSN: 0370-2693
DOI: 10.1016/j.physletb.2022.137506
Popis: 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 sNN=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's transverse momentum (pT) and rapidity (yCM) 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 〈PΛ〉(%)=6.8±1.3(stat.)±2.1(syst.) for Au+Au and 〈PΛ〉(%)=6.2±0.4(stat.)±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.
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