학술논문
Measurement of global polarization of Λ hyperons in few-GeV heavy-ion collisions
Document Type
article
Author
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
Source
Physics Letters B, Vol 835, Iss , Pp 137506- (2022)
Subject
Language
English
ISSN
0370-2693
Abstract
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.