Hyperon Polarization along the Beam Direction Relative to the Second and Third Harmonic Event Planes in Isobar Collisions at sNN =200 GeV

doi:10.1103/PhysRevLett.131.202301

Hyperon Polarization along the Beam Direction Relative to the Second and Third Harmonic Event Planes in Isobar Collisions at sNN =200 GeV

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Abstract

The polarization of Λ and Λ¯ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at sNN=200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pT dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagrees with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pT dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.

Original language	English
Article number	202301
Journal	Physical Review Letters
Volume	131
Issue number	20
DOIs	https://doi.org/10.1103/PhysRevLett.131.202301
State	Published - Nov 17 2023

Bibliographical note

Publisher Copyright:
© 2023 American Physical Society.

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, 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 Higher Education Sprout Project by Ministry of Education at NCKU, the National Research Foundation of Korea, Czech Science Foundation and Ministry of Education, Youth and Sports of the Czech Republic, Hungarian National Research, Development and Innovation Office, New National Excellency Programme of the Hungarian Ministry of Human Capacities, Department of Atomic Energy and Department of Science and Technology of the Government of India, the National Science Centre and WUT ID-UB of Poland, the Ministry of Science, Education and Sports of the Republic of Croatia, German Bundesministerium f\u00FCr Bildung, Wissenschaft, Forschung and Technologie (BMBF), Helmholtz Association, Ministry of Education, Culture, Sports, Science, and Technology (MEXT) and Japan Society for the Promotion of Science (JSPS).

Funders	Funder number
Hungarian Ministry of Human Capacities
National Research Foundation of Korea
Max Delbrück Center for Molecular Medicine in the Helmholtz Association
Ministry of Education of the People's Republic of China
Narodowe Centrum Nauki
Grantová Agentura České Republiky
U.S. Department of Energy Chinese Academy of Sciences Guangzhou Municipal Science and Technology Project Oak Ridge National Laboratory Extreme Science and Engineering Discovery Environment National Science Foundation National Energy Research Scientific Computing Center National Natural Science Foundation of China
Bundesministerium für Bildung und Forschung
Nemzeti Kutatási Fejlesztési és Innovációs Hivatal
Ministry of Education at NCKU
Ministry of Science and Technology of the People's Republic of China
Department of Atomic Energy and Department of Science and Technology
Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie
WUT ID-UB of Poland
Ministarstvo Obrazovanja, Znanosti i Sporta
Chinese Academy of Sciences
National Science Foundation Office of International Science and Engineering
Horia Hulubei National Institute for Physics and Nuclear Engineering
Ministerstvo Školství, Mládeže a Tělovýchovy
Ministry of Education, Culture, Sports, Science and Technology
National Natural Science Foundation of China (NSFC)
Not added	22K03648

ASJC Scopus subject areas

General Physics and Astronomy

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10.1103/PhysRevLett.131.202301

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@article{84d8f477d6e64988b7c963d40e2f5af8,

title = "Hyperon Polarization along the Beam Direction Relative to the Second and Third Harmonic Event Planes in Isobar Collisions at sNN =200 GeV",

abstract = "The polarization of Λ and Λ¯ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at sNN=200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pT dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagrees with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pT dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.",

author = "Abdulhamid, \{M. I.\} and Aboona, \{B. E.\} and J. Adam and Adams, \{J. R.\} and G. Agakishiev and I. Aggarwal and Aggarwal, \{M. M.\} and Z. Ahammed and A. Aitbaev and I. Alekseev and Anderson, \{D. M.\} and A. Aparin and S. Aslam and J. Atchison and Averichev, \{G. S.\} and V. Bairathi and W. Baker and Cap, \{J. G.Ball\} and K. Barish and P. Bhagat and A. Bhasin and S. Bhatta and Bordyuzhin, \{I. G.\} and Brandenburg, \{J. D.\} and Brandin, \{A. V.\} and Cai, \{X. Z.\} and H. Caines and S{\'a}nchez, \{M. Calder{\'o}n De La Barca\} and D. Cebra and J. Ceska and I. Chakaberia and Chan, \{B. K.\} and Z. Chang and A. Chatterjee and D. Chen and J. Chen and Chen, \{J. H.\} and Z. Chen and J. Cheng and Y. Cheng and S. Choudhury and W. Christie and X. Chu and Crawford, \{H. J.\} and G. Dale-Gau and A. Das and M. Daugherity and Dedovich, \{T. G.\} and Deppner, \{I. M.\} and R. Fatemi",

note = "Publisher Copyright: {\textcopyright} 2023 American Physical Society.",

year = "2023",

month = nov,

day = "17",

doi = "10.1103/PhysRevLett.131.202301",

language = "English",

volume = "131",

number = "20",

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TY - JOUR

T1 - Hyperon Polarization along the Beam Direction Relative to the Second and Third Harmonic Event Planes in Isobar Collisions at sNN =200 GeV

AU - Abdulhamid, M. I.

AU - Aboona, B. E.

AU - Adam, J.

AU - Adams, J. R.

AU - Agakishiev, G.

AU - Aggarwal, I.

AU - Aggarwal, M. M.

AU - Ahammed, Z.

AU - Aitbaev, A.

AU - Alekseev, I.

AU - Anderson, D. M.

AU - Aparin, A.

AU - Aslam, S.

AU - Atchison, J.

AU - Averichev, G. S.

AU - Bairathi, V.

AU - Baker, W.

AU - Cap, J. G.Ball

AU - Barish, K.

AU - Bhagat, P.

AU - Bhasin, A.

AU - Bhatta, S.

AU - Bordyuzhin, I. G.

AU - Brandenburg, J. D.

AU - Brandin, A. V.

AU - Cai, X. Z.

AU - Caines, H.

AU - Sánchez, M. Calderón De La Barca

AU - Cebra, D.

AU - Ceska, J.

AU - Chakaberia, I.

AU - Chan, B. K.

AU - Chang, Z.

AU - Chatterjee, A.

AU - Chen, D.

AU - Chen, J.

AU - Chen, J. H.

AU - Chen, Z.

AU - Cheng, J.

AU - Cheng, Y.

AU - Choudhury, S.

AU - Christie, W.

AU - Chu, X.

AU - Crawford, H. J.

AU - Dale-Gau, G.

AU - Das, A.

AU - Daugherity, M.

AU - Dedovich, T. G.

AU - Deppner, I. M.

AU - Fatemi, R.

PY - 2023/11/17

Y1 - 2023/11/17

N2 - The polarization of Λ and Λ¯ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at sNN=200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pT dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagrees with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pT dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.

AB - The polarization of Λ and Λ¯ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at sNN=200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pT dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagrees with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pT dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.

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U2 - 10.1103/PhysRevLett.131.202301

DO - 10.1103/PhysRevLett.131.202301

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SN - 0031-9007

VL - 131

JO - Physical Review Letters

JF - Physical Review Letters

IS - 20

M1 - 202301

ER -

Hyperon Polarization along the Beam Direction Relative to the Second and Third Harmonic Event Planes in Isobar Collisions at sNN =200 GeV

Abstract

Bibliographical note

Funding

ASJC Scopus subject areas

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