1. Measurement of global polarization of Λ hyperons in few-GeV heavy-ion collisions
- Author
-
Abou Yassine, R., Adamczewski-Musch, J., Cordts, M., Wasiluk, M., Weber, A. A., Wendisch, C., Wirth, J., Zbroszczyk, H. P., Zherebtsova, E., Zielinski, M., Zumbruch, P., HADES collaboration, Dreyer, J., Esmail, W. A., Fabbietti, L., Floersheimer, H., Fonte, P., Friese, J., Fröhlich, I., Förtsch, J., Galatyuk, T., Asal, C., Gniazdowski, T., Greifenhagen, R., Grunwald, M., Gumberidze, M., Harabasz, S., Heinz, T., Höhne, C., Hojeij, F., Holzmann, R., Huck, H., Becker, M., Idzik, M., Kämpfer, B., Kampert, K-H., Kardan, B., Kedych, V., Koenig, I., Koenig, Wolfgang, Kohls, M., Kolas, J., Kornakov, G., Belounnas, A., Kotte, R., Kres, I., Krueger, W., Kugler, A., Lalik, R., Lebedev, S., Linev, S., Linz, F., Lopes, L., Lorenz, M., Blanco, A., Malige, A., Markert, J., Matulewicz, T., Maurus, S., Metag, V., Michel, J., Molenda, A., Müntz, C., Nabroth, M., Naumann, L., Blume, C., Nowakowski, K., Orliński, J., Otto, J.-H., Parschau, M., Pauly, C., Pechenova, O., Pechenov, V., Pfeifer, D., Piasecki, K., Pietraszko, J., Chlad, L., Povar, T., Prozorov, A., Przygoda, W., Pysz, K., Ramstein, B., Rathod, N., Ritman, J., Rodriguez-Ramos, P., Rost, A., Rustamov, A., Chudoba, P., Salabura, P., Saraiva, J., Schild, N., Schwab, E., Scozzi, F., Seck, F., Selyuzhenkov, I., Singh, U., Skorpil, L., Smyrski, J., Ciepał, I., Spies, S., Stefaniak, M. S., Ströbele, H., Stroth, J., Sumara, K., Svoboda, O., Szala, M., Tlusty, P., Traxler, M., and Wagner, V.
- Subjects
Nuclear and High Energy Physics ,Nuclear Theory ,FOS: Physical sciences ,ddc:530 ,High Energy Physics::Experiment ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment - 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
- Published
- 2022
- Full Text
- View/download PDF