Global polarization of Λ and Λ[bar] hyperons in Au+Au collisions at √sNN=19.6 and 27 GeV
In relativistic heavy-ion collisions, a global spin polarization, PH, of Λ and Λ[bar] hyperons along the direction of the system angular momentum was discovered and measured across a broad range of collision energies and demonstrated a trend of increasing PH with decreasing √sNN. A splitting between...
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| Main Authors: | , , , , , |
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| Corporate Author: | |
| Format: | Article (Journal) |
| Language: | English |
| Published: |
27 July 2023
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| In: |
Physical review
Year: 2023, Volume: 108, Issue: 1, Pages: 1-9 |
| ISSN: | 2469-9993 |
| DOI: | 10.1103/PhysRevC.108.014910 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1103/PhysRevC.108.014910 Verlag, lizenzpflichtig, Volltext: https://link.aps.org/doi/10.1103/PhysRevC.108.014910 
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| Author Notes: | STAR Collaboration* |
| Summary: | In relativistic heavy-ion collisions, a global spin polarization, PH, of Λ and Λ[bar] hyperons along the direction of the system angular momentum was discovered and measured across a broad range of collision energies and demonstrated a trend of increasing PH with decreasing √sNN. A splitting between Λ and Λ[bar] polarization may be possible due to their different magnetic moments in a late-stage magnetic field sustained by the quark-gluon plasma which is formed in the collision. The results presented in this study find no significant splitting at the collision energies of √sNN=19.6 and 27 GeV in the BNL Relativistic Heavy Ion Collisions Beam Energy Scan Phase II using the STAR detector, with an upper limit of PΛ[bar]−PΛ<0.24% and PΛ[bar]−PΛ<0.35%, respectively, at a 95% confidence level. We derive an upper limit on the naive extraction of the late-stage magnetic field of B<9.4×1012 T and B<1.4×1013 T at √sNN=19.6 and 27 GeV, respectively, although more thorough derivations are needed. Differential measurements of PH were performed with respect to collision centrality, transverse momentum, and rapidity. With our current acceptance of |y|<1 and uncertainties, we observe no dependence on transverse momentum and rapidity in this analysis. These results challenge multiple existing model calculations following a variety of different assumptions which have each predicted a strong dependence on rapidity in this collision-energy range. |
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| Item Description: | *STAR Collaboration: M.I. Abdulhamid, I.M. Deppner, N. Herrmann, Y.H. Leung, Y. Söhngen, P.C. Weidenkaff [und 370 weitere Personen] Im Titel steht der zweite Buchstabe Lambda mit einem Oberstrich Im Titel steht der Ausdruck "sNN" unter dem Wurzelsymbol Gesehen am 30.01.2024 |
| Physical Description: | Online Resource |
| ISSN: | 2469-9993 |
| DOI: | 10.1103/PhysRevC.108.014910 |