Hyperon global polarization in isobar Ru+Ru and Zr+Zr collisions at $$\sqrt{s_{NN}}$$ = 200GeV

Journal Article · Wed Oct 01 00:00:00 UTC 2025 · Physics Letters. B

DOI: https://doi.org/10.1016/j.physletb.2025.139891 · OSTI ID:3012642

Aboona, B. E. ^[1]; Adam, J.; Agakishiev, G.; Aggarwal, I.; Aggarwal, M.M.; Ahammed, Z.; Aitbayev, A.; Alekseev, I.; Alpatov, E.; Alshammri, A.K.; Aparin, A.; Aslam, S.; Atchison, J.; Averichev, G.S.; Bairathi, V.; Bao, X.; Barik, P.; Barish, Kenneth; Behera, S.; Bhagat, P. ; Bhasin, A.; Bhatta, S.; Bordyuzhin, I.G.; Brandenburg, J.D.; Brandin, A.V.; Broodo, C.; Cai, X.Z.; Caines, H.; de La Barca Sánchez, M. Calderón; Cebra, D.; Ceska, J.; Chakaberia, I.; Chang, Y.S.; Chang, Z.; Chatterjee, A.; Chen, D.; Chen, J.H.; Chen, Q.; Chen, W.; Chen, Z.; Cheng, J.; Cheng, Y.; Christie, W.; Chu, X.; Corey, S.; Crawford, H.J.; Csanad, M.; Dale-Gau, G.; Das, A.; Dedovich, T.G.; Deppner, I.M.; Derevschikov, A.A.; Deshpande, A.; Dhamija, A.; Dimri, A.; Dixit, P.; Dong, X.; Drachenberg, J.L.; Duckworth, E.; Dunlop, J.C.; El-Feky, Y.S.; Engelage, J.; Eppley, G.; Esumi, S.; Evdokimov, O.; Eyser, O.; Fan, B.; Fatemi, R.; Fazio, S.; Feng, H.; Feng, Y.; Finch, E.; Fisyak, Y.; Flor, F.A.; Fu, C.; Fu, T.; Gao, T.; Gao, Y.; Geurts, F.; Gibson, A.; Gopal, K.; Gou, X. ; Grosnick, D.; Gu, A.; Gupta, A.; Guryn, W.; Hamed, A.; Hamilton, R.J.; Han, J.; Han, X.; Harasty, M.D.; Harris, J.W.; Harrison-Smith, H.; Havener, L.B.; He, X.H.; He, Y.; Hu, C.; Hu, Q.; Hu, Y.; Huang, H.; Huang, H.Z.; Huang, S.L.; Huang, T.; Huang, Y.; Huang, Y.; Huang, Y.; Isshiki, M.; Jacobs, W.W.; Jalotra, A.; Jena, C.; Ji, Y.; Jia, J.; Jiang, X.; Jin, C.; Jin, Y.; Jindal, N.; Ju, X.; Judd, E.G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kapukchyan, D.; Kauder, K.; Keane, D.; Kechechyan, A.; Kesler, M.; Khanal, A.; Kim, J.; Kiselev, A.; Knospe, A.G.; Kochenda, L.; Korobitsin, A.A.; Korodi, B.; Kraeva, A. Yu; Kravtsov, P.; Kumar, L.; Labonte, M.C.; Lacey, R.; Landgraf, J.M.; Larson, C.; Lebedev, A.; Lednicky, R.; Lee, J.H.; Leung, Y.H.; Li, C.; Li, D.; Li, H-S; Li, H.; Li, H.; Li, H.; Li, W.; Li, X.; Li, X.; Li, Y.; Li, Z.; Li, Z.; Liang, X.; Lin, T.; Lin, Y.; Liu, C.; Liu, G.; Liu, H.; Liu, L.; Liu, L.; Liu, Z.; Liu, Z.; Ljubicic, T.; Lomicky, O.; Loyd, E.M.; Lu, T.; Luo, J.; Luo, X.F.; Luong, V.B.; Ma, L.; Ma, R.; Ma, Y.G.; Magdy, N.; Manikandhan, R.; Margetis, S.; Matonoha, O.; Mi, K.; Minaev, N.G.; Mohanty, B.; Mondal, B.; Mondal, M.M.; Mooney, I.; Morozov, D.A.; Nagy, M.I.; Naim, C.J.; Nain, A.S.; Nam, J.D.; Nasim, M.; Nasrulloh, H.; Nedorezov, E.; Nelson, J.M.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L.V.; Nonaka, T.; Odyniec, G.; Ogawa, A.; Oh, S.; Okorokov, V.A.; Okubo, K.; Page, B.S.; Pal, S.; Pandav, A.; Panday, A.; Pandey, A.K.; Panebratsev, Y.; Pani, T.; Parfenov, P.; Paul, A.; Paul, S.; Perkins, C.; Ping, S.; Pokhrel, B.R.; Ponce Pinto, I.D.; Posik, M.; Pottebaum, E.; Povarov, A.; Prodhan, S.; Protzman, T.L.; Pruthi, N.K.; Putschke, J.; Qi, Y.; Qin, Z.; Qiu, H.; Racz, C.; Radhakrishnan, S.K.; Rana, A.; Ray, R.L.; Robertson, C.W.; Rogachevsky, O.V.; Rosales Aguilar, M.A.; Roy, D.; Ruan, L.; Sahoo, A.K.; Sahoo, N.R.; Sako, H.; Salur, S.; Sambyal, S.S.; Samigullin, E.; Sandhu, J.K.; Sato, S.; Schaefer, B.C.; Schmitz, N.; Seger, J.; Seto, R.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P.V.; Shao, T.; Sharma, M.; Sharma, N.; Sharma, R.; Sharma, S.R.; Sheikh, A.I.; Shen, D.; Shen, D.Y.; Shen, K.; Shi, S.; Shi, Y.; Si, F.; Singh, J.; Singha, S.; Sinha, P.; Skoby, M.J.; Söhngen, Y.; Song, Y.; Stanislaus, T. D S; Strikhanov, M.; Su, Y.; Sun, X.; Sun, Y.; Surrow, B.; Svirida, D.N.; Sweger, Z.W.; Tamis, A.C.; Tang, A.H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Thomas, J.H.; Timofeev, A.; Tlusty, D.; Tokarev, M.V.; Torres Valladares, D.; Trentalange, S.; Tribedy, P.; Tsai, O.D.; Tsang, C.Y.; Tu, Z.; Tyler, J.E.; Ullrich, T.; Underwood, D.G.; Van Buren, G.; Vasiliev, A.N.; Videbæk, F.; Vokal, S.; Voloshin, S.A.; Wang, F.; Wang, G.; Wang, G.; Wang, J.S.; Wang, J.; Wang, K.; Wang, X.; Wang, Y.; Wang, Y.; Wang, Y.; Wang, Z.; Wang, Z.; Webb, J.C.; Weidenkaff, P.C.; Westfall, G.D.; Wieman, H.; Wilks, G.; Wissink, S.W.; Wong, C.P.; Wu, J.; Wu, X.; Wu, X.; Wu, X.; Xi, B.; Xiao, Y.; Xiao, Z.G.; Xie, G.; Xie, W.; Xu, H.; Xu, N.; Xu, Q.H.; Xu, Y.; Xu, Y.; Xu, Y.; Xu, Y.; Xu, Z.; Xu, Z.; Yan, G.; Yan, Z.; Yang, C.; Yang, Q.; Yang, S.; Yang, Y.; Ye, Z.; Ye, Z.; Yi, L.; Yu, Y.; Zha, W.; Zhang, C.; Zhang, D.; Zhang, J.; Zhang, L.; Zhang, S.; Zhang, W.; Zhang, X.; Zhang, Y.; Zhang, Y.; Zhang, Y.; Zhang, Y.; Zhang, Z.; Zhang, Z.; Zhao, F.; Zhao, J.; Zhou, S.; Zhou, Y.; Zhu, X.; Zurek, M.; Zyzak, M.

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1. Texas A & M Univ., College Station, TX (United States); STAR Collaboration. et al.

The polarization of Λ, $$\overline{Λ}$$, $$Ξ$$^–, and $$\overline{Ξ}$$⁺ hyperons along the angular momentum of the system has been measured in isobar collisions of Ru+Ru and Zr+Zr at $$\sqrt{s_{NN}}$$ = 200 GeV with the STAR detector at RHIC. The polarization dependence on collision centrality exhibits an increasing trend in more peripheral collisions. Λ and $$\overline{Λ}$$ polarization dependence on the transverse momentum and pseudorapidity have been investigated, but no significant dependence was observed. The polarizations of Λ and $$\overline{Λ}$$ are found to be consistent with each other, indicating little contribution of the spin-magnetic coupling to the measured polarization. Comparison to previously measured polarization in Au+Au collisions show no obvious system size dependence. The results are qualitatively consistent with hydrodynamic calculations including contributions from shear-induced polarization and thermal vorticity. For the first time in heavy-ion collisions, the dependence of the global polarization on the hyperon’s emission azimuthal angle relative to the second-order event plane has been measured, indicating stronger polarization for the in-plane emitted hyperons at the level of 2.4σ significance in 20–50 % centrality. The $$Ξ$$ hyperon polarization measurements via polarization transfer analysis yield finite positive values with 2.9σ significance in 20–50 % centrality, slightly larger compared to the inclusive Λ polarization.

• Research Organization: Abilene Christian Univ., TX (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States). Relativistic Heavy Ion Collider (RHIC); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Temple Univ., Philadelphia, PA (United States); Univ. of California, Riverside, CA (United States); Wayne State University, Detroit, MI (United States); Yale University, New Haven, CT (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), High Energy Physics (HEP); USDOE Office of Science (SC), Nuclear Physics (NP)
• Contributing Organization: STAR Collaboration
• Grant/Contract Number: AC02-05CH11231; FG02-03ER41243; FG02-04ER41325; FG02-92ER40713; SC0004168; SC0012704; SC0013405
• OSTI ID: 3012642
• Report Number(s): BNL--228167-2025-JAAM; arXiv:2505.05046 [nucl-ex]
• Journal Information: Physics Letters. B, Journal Name: Physics Letters. B Vol. 870; ISSN 0370-2693
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English