Onset of Constituent Quark Number Scaling in Heavy-Ion Collisions at RHIC

doi:10.1103/2qhx-cp79

Onset of Constituent Quark Number Scaling in Heavy-Ion Collisions at RHIC

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Abstract

Partonic collectivity is one of the necessary signatures for the formation of quark-gluon plasma in high-energy nuclear collisions. Number of constituent quarks (NCQ) scaling has been observed for hadron elliptic flow v2 in top energy nuclear collisions at the Relativistic Heavy Ion Collider and the LHC, and this has been theoretically suggested as strong evidence for partonic collectivity. In this Letter, a systematic analysis of v2 of π±, K±, KS0, p, and Λ in Au+Au collisions at sNN=3.2, 3.5, 3.9, and 4.5 GeV, with the STAR experiment at the Relativistic Heavy Ion Collider, is presented. NCQ scaling is markedly violated at 3.2 GeV, consistent with a hadronic-interaction dominated equation of state. However, as the collision energy increases, a gradual evolution to NCQ scaling is observed. This beam-energy dependence of v2 for all hadrons studied provides evidence for the onset of dominant partonic interactions by sNN=4.5 GeV.

Original language	English
Article number	072301
Journal	Physical Review Letters
Volume	135
Issue number	7
DOIs	https://doi.org/10.1103/2qhx-cp79
State	Published - Aug 15 2025

Bibliographical note

Publisher Copyright:
© 2025 American Physical Society.

Funding

We thank the RHIC Operations Group and SDCC 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 Science and Technology of China and the Chinese Ministry of Education, National Natural Science Foundation of China, Chinese Academy of Science, NSTC Taipei, 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 für 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
National Research Foundation of Korea
Max Delbrück Center for Molecular Medicine in the Helmholtz Association
Narodowe Centrum Nauki
Grantová Agentura České Republiky
National Science Foundation Arctic Social Science Program
Japan Society for the Promotion of Science
US DOE Office of Science
Emberi Eroforrások Minisztériuma
Bundesministerium für Forschung, Technologie und Raumfahrt
Qianjiang Talents Project of Science and Technology Department of Zhejiang Province
Nemzeti Kutatási Fejlesztési és Innovációs Hivatal
Changjiang Scholar Program of Chinese Ministry of Education
Ministry of Science and Technology of the People's Republic of China
National Science and Technology Council
Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie
WUT ID-UB of Poland
Ministarstvo Obrazovanja, Znanosti i Sporta
Chinese Academy of Sciences
Institute for Nuclear Physics
Ministerstvo Školství, Mládeže a Tělovýchovy
Ministry of Education, Culture, Sports, Science and Technology
National Natural Science Foundation of China (NSFC)

ASJC Scopus subject areas

General Physics and Astronomy

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10.1103/2qhx-cp79

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@article{be31f1e7d2dc4cae9f92566f32b2cf90,

title = "Onset of Constituent Quark Number Scaling in Heavy-Ion Collisions at RHIC",

abstract = "Partonic collectivity is one of the necessary signatures for the formation of quark-gluon plasma in high-energy nuclear collisions. Number of constituent quarks (NCQ) scaling has been observed for hadron elliptic flow v2 in top energy nuclear collisions at the Relativistic Heavy Ion Collider and the LHC, and this has been theoretically suggested as strong evidence for partonic collectivity. In this Letter, a systematic analysis of v2 of π±, K±, KS0, p, and Λ in Au+Au collisions at sNN=3.2, 3.5, 3.9, and 4.5 GeV, with the STAR experiment at the Relativistic Heavy Ion Collider, is presented. NCQ scaling is markedly violated at 3.2 GeV, consistent with a hadronic-interaction dominated equation of state. However, as the collision energy increases, a gradual evolution to NCQ scaling is observed. This beam-energy dependence of v2 for all hadrons studied provides evidence for the onset of dominant partonic interactions by sNN=4.5 GeV.",

author = "Aboona, \{B. E.\} and J. Adam and L. Adamczyk and I. Aggarwal and Aggarwal, \{M. M.\} and Z. Ahammed and Alshammri, \{A. K.\} and Aschenauer, \{E. C.\} and S. Aslam and J. Atchison and V. Bairathi and X. Bao and K. Barish and S. Behera and R. Bellwied and P. Bhagat and A. Bhasin and S. Bhatta and Bhosale, \{S. R.\} and J. Bielcik and J. Bielcikova and Brandenburg, \{J. D.\} and C. Broodo and Cai, \{X. Z.\} and H. Caines and \{Calder{\'o}n De La Barca S{\'a}nchez\}, M. and D. Cebra and J. Ceska and I. Chakaberia and P. Chaloupka and Chan, \{B. K.\} and Z. Chang and A. Chatterjee and D. Chen and J. Chen and Chen, \{J. H.\} and Q. Chen and Z. Chen and J. Cheng and Y. Cheng and W. Christie and X. Chu and S. Corey and Crawford, \{H. J.\} and M. Csan{\'a}d and G. Dale-Gau and A. Das and Deppner, \{I. M.\} and A. Deshpande and R. Fatemi",

note = "Publisher Copyright: {\textcopyright} 2025 American Physical Society.",

year = "2025",

month = aug,

day = "15",

doi = "10.1103/2qhx-cp79",

language = "English",

volume = "135",

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AU - Aboona, B. E.

AU - Adam, J.

AU - Adamczyk, L.

AU - Aggarwal, I.

AU - Aggarwal, M. M.

AU - Ahammed, Z.

AU - Alshammri, A. K.

AU - Aschenauer, E. C.

AU - Aslam, S.

AU - Atchison, J.

AU - Bairathi, V.

AU - Bao, X.

AU - Barish, K.

AU - Behera, S.

AU - Bellwied, R.

AU - Bhagat, P.

AU - Bhasin, A.

AU - Bhatta, S.

AU - Bhosale, S. R.

AU - Bielcik, J.

AU - Bielcikova, J.

AU - Brandenburg, J. D.

AU - Broodo, C.

AU - Cai, X. Z.

AU - Caines, H.

AU - Calderón De La Barca Sánchez, M.

AU - Cebra, D.

AU - Ceska, J.

AU - Chakaberia, I.

AU - Chaloupka, P.

AU - Chan, B. K.

AU - Chang, Z.

AU - Chatterjee, A.

AU - Chen, D.

AU - Chen, J.

AU - Chen, J. H.

AU - Chen, Q.

AU - Chen, Z.

AU - Cheng, J.

AU - Cheng, Y.

AU - Christie, W.

AU - Chu, X.

AU - Corey, S.

AU - Crawford, H. J.

AU - Csanád, M.

AU - Dale-Gau, G.

AU - Das, A.

AU - Deppner, I. M.

AU - Deshpande, A.

AU - Fatemi, R.

PY - 2025/8/15

Y1 - 2025/8/15

N2 - Partonic collectivity is one of the necessary signatures for the formation of quark-gluon plasma in high-energy nuclear collisions. Number of constituent quarks (NCQ) scaling has been observed for hadron elliptic flow v2 in top energy nuclear collisions at the Relativistic Heavy Ion Collider and the LHC, and this has been theoretically suggested as strong evidence for partonic collectivity. In this Letter, a systematic analysis of v2 of π±, K±, KS0, p, and Λ in Au+Au collisions at sNN=3.2, 3.5, 3.9, and 4.5 GeV, with the STAR experiment at the Relativistic Heavy Ion Collider, is presented. NCQ scaling is markedly violated at 3.2 GeV, consistent with a hadronic-interaction dominated equation of state. However, as the collision energy increases, a gradual evolution to NCQ scaling is observed. This beam-energy dependence of v2 for all hadrons studied provides evidence for the onset of dominant partonic interactions by sNN=4.5 GeV.

AB - Partonic collectivity is one of the necessary signatures for the formation of quark-gluon plasma in high-energy nuclear collisions. Number of constituent quarks (NCQ) scaling has been observed for hadron elliptic flow v2 in top energy nuclear collisions at the Relativistic Heavy Ion Collider and the LHC, and this has been theoretically suggested as strong evidence for partonic collectivity. In this Letter, a systematic analysis of v2 of π±, K±, KS0, p, and Λ in Au+Au collisions at sNN=3.2, 3.5, 3.9, and 4.5 GeV, with the STAR experiment at the Relativistic Heavy Ion Collider, is presented. NCQ scaling is markedly violated at 3.2 GeV, consistent with a hadronic-interaction dominated equation of state. However, as the collision energy increases, a gradual evolution to NCQ scaling is observed. This beam-energy dependence of v2 for all hadrons studied provides evidence for the onset of dominant partonic interactions by sNN=4.5 GeV.

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UR - https://www.scopus.com/pages/publications/105015680989#tab=citedBy

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DO - 10.1103/2qhx-cp79

M3 - Article

C2 - 40929191

AN - SCOPUS:105015680989

SN - 0031-9007

VL - 135

JO - Physical Review Letters

JF - Physical Review Letters

IS - 7

M1 - 072301

ER -

Onset of Constituent Quark Number Scaling in Heavy-Ion Collisions at RHIC

Abstract

Bibliographical note

Funding

ASJC Scopus subject areas

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