Global polarization of Λ hyperons in Au + Au collisions at sNN =200 GeV

STAR Collaboration

doi:10.1103/PhysRevC.98.014910

Global polarization of Λ hyperons in Au + Au collisions at sNN =200 GeV

STAR Collaboration

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Abstract

Global polarization of Λ hyperons has been measured to be of the order of a few tenths of a percentage in Au+Au collisions at sNN = 200 GeV, with no significant difference between Λ and Λ. These new results reveal the collision energy dependence of the global polarization together with the results previously observed at sNN = 7.7-62.4 GeV and indicate noticeable vorticity of the medium created in noncentral heavy-ion collisions at the highest Relativistic Heavy Ion Collider collision energy. The signal is in rough quantitative agreement with the theoretical predictions from a hydrodynamic model and from a multi-phase transport model. The polarization is larger in more peripheral collisions, and depends weakly on the hyperon's transverse momentum and pseudorapidity ηH within |ηH|<1. An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the 2σ level, suggesting a possible contribution to the polarization from the axial current induced by the initial magnetic field.

Original language	English
Article number	014910
Journal	Physical Review C
Volume	98
Issue number	1
DOIs	https://doi.org/10.1103/PhysRevC.98.014910
State	Published - Jul 23 2018
Externally published	Yes

Funding

We thank the RHIC Operations Group and RCF at BNL, the NERSC Center at LBNL, and the Open Science Grid consortium for providing resources and support. This work was supported in part by the Office of Nuclear Physics within the U.S. DOE Office of Science; the U.S. National Science Foundation; the Ministry of Education and Science of the Russian Federation; National Natural Science Foundation of China; Chinese Academy of Science; the Ministry of Science and Technology of China and the Chinese Ministry of Education; the National Research Foundation of Korea; Czech Science Foundation and Ministry of Education, Youth and Sports of the Czech Republic; Department of Atomic Energy and Department of Science and Technology of the Government of India; the National Science Centre of Poland; the Ministry of Science, Education and Sports of the Republic of Croatia; RosAtom of Russia and German Bundesministerium fur Bildung, Wissenschaft, Forschung and Technologie (BMBF); and the Helmholtz Association.

Funders	Funder number
Department of Atomic Energy and Department of Science and Technology
RosAtom of Russia and German Bundesministerium fur Bildung, Wissenschaft, Forschung and Technologie
National Science Foundation	1614545
National Science Foundation
Office of Science
Nuclear Physics
Lawrence Berkeley National Laboratory
National Natural Science Foundation of China
Ministerstvo Školství, Mládeže a Tělovýchovy
Grantová Agentura České Republiky
Ministry of Education of the People's Republic of China
Bundesministerium für Bildung und Forschung
Chinese Academy of Sciences
Ministry of Science and Technology of the People's Republic of China
Ministarstvo Obrazovanja, Znanosti i Sporta
Ministry of Education and Science of the Russian Federation
National Research Foundation of Korea
Narodowe Centrum Nauki
Ministry of Education and Science
Helmholtz Association

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10.1103/PhysRevC.98.014910

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@article{7ef4a3825c7e41f0bf1e1b2aee68719f,

title = "Global polarization of Λ hyperons in Au + Au collisions at sNN =200 GeV",

abstract = "Global polarization of Λ hyperons has been measured to be of the order of a few tenths of a percentage in Au+Au collisions at sNN = 200 GeV, with no significant difference between Λ and Λ. These new results reveal the collision energy dependence of the global polarization together with the results previously observed at sNN = 7.7-62.4 GeV and indicate noticeable vorticity of the medium created in noncentral heavy-ion collisions at the highest Relativistic Heavy Ion Collider collision energy. The signal is in rough quantitative agreement with the theoretical predictions from a hydrodynamic model and from a multi-phase transport model. The polarization is larger in more peripheral collisions, and depends weakly on the hyperon's transverse momentum and pseudorapidity ηH within |ηH|<1. An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the 2σ level, suggesting a possible contribution to the polarization from the axial current induced by the initial magnetic field.",

author = "{STAR Collaboration} and J. Adam and L. Adamczyk and Adams, {J. R.} and Adkins, {J. K.} and G. Agakishiev and Aggarwal, {M. M.} and Z. Ahammed and Ajitanand, {N. N.} and I. Alekseev and Anderson, {D. M.} and R. Aoyama and A. Aparin and D. Arkhipkin and Aschenauer, {E. C.} and Ashraf, {M. U.} and F. Atetalla and A. Attri and Averichev, {G. S.} and X. Bai and V. Bairathi and K. Barish and Bassill, {A. J.} and A. Behera and R. Bellwied and A. Bhasin and Bhati, {A. K.} and J. Bielcik and J. Bielcikova and Bland, {L. C.} and Bordyuzhin, {I. G.} and Brandenburg, {J. D.} and Brandin, {A. V.} and D. Brown and J. Bryslawskyj and I. Bunzarov and J. Butterworth and H. Caines and {Calder{\'o}n De La Barca S{\'a}nchez}, M. and Campbell, {J. M.} and D. Cebra and I. Chakaberia and P. Chaloupka and Chang, {F. H.} and Z. Chang and N. Chankova-Bunzarova and A. Chatterjee and S. Chattopadhyay and Chen, {J. H.} and X. Chen and J. Schambach",

note = "Publisher Copyright: {\textcopyright} 2018 American Physical Society.",

year = "2018",

month = jul,

day = "23",

doi = "10.1103/PhysRevC.98.014910",

language = "English",

volume = "98",

journal = "Physical Review C",

issn = "2469-9985",

publisher = "American Physical Society",

number = "1",

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TY - JOUR

T1 - Global polarization of Λ hyperons in Au + Au collisions at sNN =200 GeV

AU - STAR Collaboration

AU - Adam, J.

AU - Adamczyk, L.

AU - Adams, J. R.

AU - Adkins, J. K.

AU - Agakishiev, G.

AU - Aggarwal, M. M.

AU - Ahammed, Z.

AU - Ajitanand, N. N.

AU - Alekseev, I.

AU - Anderson, D. M.

AU - Aoyama, R.

AU - Aparin, A.

AU - Arkhipkin, D.

AU - Aschenauer, E. C.

AU - Ashraf, M. U.

AU - Atetalla, F.

AU - Attri, A.

AU - Averichev, G. S.

AU - Bai, X.

AU - Bairathi, V.

AU - Barish, K.

AU - Bassill, A. J.

AU - Behera, A.

AU - Bellwied, R.

AU - Bhasin, A.

AU - Bhati, A. K.

AU - Bielcik, J.

AU - Bielcikova, J.

AU - Bland, L. C.

AU - Bordyuzhin, I. G.

AU - Brandenburg, J. D.

AU - Brandin, A. V.

AU - Brown, D.

AU - Bryslawskyj, J.

AU - Bunzarov, I.

AU - Butterworth, J.

AU - Caines, H.

AU - Calderón De La Barca Sánchez, M.

AU - Campbell, J. M.

AU - Cebra, D.

AU - Chakaberia, I.

AU - Chaloupka, P.

AU - Chang, F. H.

AU - Chang, Z.

AU - Chankova-Bunzarova, N.

AU - Chatterjee, A.

AU - Chattopadhyay, S.

AU - Chen, J. H.

AU - Chen, X.

AU - Schambach, J.

PY - 2018/7/23

Y1 - 2018/7/23

N2 - Global polarization of Λ hyperons has been measured to be of the order of a few tenths of a percentage in Au+Au collisions at sNN = 200 GeV, with no significant difference between Λ and Λ. These new results reveal the collision energy dependence of the global polarization together with the results previously observed at sNN = 7.7-62.4 GeV and indicate noticeable vorticity of the medium created in noncentral heavy-ion collisions at the highest Relativistic Heavy Ion Collider collision energy. The signal is in rough quantitative agreement with the theoretical predictions from a hydrodynamic model and from a multi-phase transport model. The polarization is larger in more peripheral collisions, and depends weakly on the hyperon's transverse momentum and pseudorapidity ηH within |ηH|<1. An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the 2σ level, suggesting a possible contribution to the polarization from the axial current induced by the initial magnetic field.

AB - Global polarization of Λ hyperons has been measured to be of the order of a few tenths of a percentage in Au+Au collisions at sNN = 200 GeV, with no significant difference between Λ and Λ. These new results reveal the collision energy dependence of the global polarization together with the results previously observed at sNN = 7.7-62.4 GeV and indicate noticeable vorticity of the medium created in noncentral heavy-ion collisions at the highest Relativistic Heavy Ion Collider collision energy. The signal is in rough quantitative agreement with the theoretical predictions from a hydrodynamic model and from a multi-phase transport model. The polarization is larger in more peripheral collisions, and depends weakly on the hyperon's transverse momentum and pseudorapidity ηH within |ηH|<1. An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the 2σ level, suggesting a possible contribution to the polarization from the axial current induced by the initial magnetic field.

UR - http://www.scopus.com/inward/record.url?scp=85050823340&partnerID=8YFLogxK

U2 - 10.1103/PhysRevC.98.014910

DO - 10.1103/PhysRevC.98.014910

M3 - Article

AN - SCOPUS:85050823340

SN - 2469-9985

VL - 98

JO - Physical Review C

JF - Physical Review C

IS - 1

M1 - 014910

ER -

Global polarization of Λ hyperons in Au + Au collisions at sNN =200 GeV

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