Measurement of kaon directed flow in Au+Au collisions in the high baryon density region

M.Zyzakstar-publication@bnl.govThe STAR Collaboration

doi:10.1016/j.physletb.2026.140353

Measurement of kaon directed flow in Au+Au collisions in the high baryon density region

[email protected] STAR Collaboration

Texas A&M University
Czech Technical University in Prague
Joint Institute for Nuclear Research
Panjab University
Variable Energy Cyclotron Centre India
Alikhanov Institute for Theoretical and Experimental Physics
Moscow Engineering Physics Institute
Kent State University
Fudan University
Abilene Christian University
Universidad de Tarapacá
Shandong University
Indian Institute of Science Education and Research, Berhampur
University of California at Riverside
Indian Institute of Science Education and Research, Tirupati
University of Jammu
Stony Brook University
Ohio State University
University of Houston
Chinese Academy of Sciences
Yale University
University of California at Davis
Lawrence Berkeley National Laboratory
Purdue University
Indiana University Bloomington
National Institute of Technology, Durgapur
Central China Normal University
Guangxi Normal University
Tsinghua University
University of California at Los Angeles
Brookhaven National Laboratory
University of California at Berkeley

Research output: Contribution to journal › Article › peer-review

Abstract

Rapidity-odd directed flow v ₁ measurements are presented for K ^± and K_S⁰ in Au + Au collisions for s_NN from 3.0 to 3.9 GeV with the STAR experiment. For comparison, v ₁ of π ^±, protons, and Λ from the same collisions are also discussed. The mid-rapidity v ₁ slope dv₁/dy|_y=0 for protons and Λ is positive in these collisions. On the other hand, v ₁ slope of kaons exhibits a strong p_T dependence: negative at p_T< 0.6 GeV/ c and positive at higher p_T. A similar p_T dependence is also evident for the v ₁ slope of charged pions. Compared to the spectator-removed calculations in Au+Au collisions at s_NN= 3.0–3.9 GeV, the JAM model demonstrates a pronounced shift of the v ₁ slopes of mesons towards the negative direction. It suggests that the shadowing effect of the spectators plays an important role in the observed kaon anti-flow at low p_T in the high baryon density region of non-central collisions.

Original language	English
Article number	140353
Journal	Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume	875
DOIs	https://doi.org/10.1016/j.physletb.2026.140353
State	Published - Apr 2026

Keywords

Directed flow
Heavy-ion collisions
High baryon density region
Kaon potential
QCD phase structure
Spectator effect

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10.1016/j.physletb.2026.140353

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@article{83a2de32101d4a72a578de948a43e6d6,

title = "Measurement of kaon directed flow in Au+Au collisions in the high baryon density region",

abstract = "Rapidity-odd directed flow v 1 measurements are presented for K ± and KS0 in Au + Au collisions for sNN from 3.0 to 3.9 GeV with the STAR experiment. For comparison, v 1 of π ± , protons, and Λ from the same collisions are also discussed. The mid-rapidity v 1 slope dv1/dy|y=0 for protons and Λ is positive in these collisions. On the other hand, v 1 slope of kaons exhibits a strong pT dependence: negative at pT< 0.6 GeV/ c and positive at higher pT. A similar pT dependence is also evident for the v 1 slope of charged pions. Compared to the spectator-removed calculations in Au+Au collisions at sNN= 3.0{\textendash}3.9 GeV, the JAM model demonstrates a pronounced shift of the v 1 slopes of mesons towards the negative direction. It suggests that the shadowing effect of the spectators plays an important role in the observed kaon anti-flow at low pT in the high baryon density region of non-central collisions.",

keywords = "Directed flow, Heavy-ion collisions, High baryon density region, Kaon potential, QCD phase structure, Spectator effect",

author = "\{[email protected] STAR Collaboration\} and Aboona, \{B. E.\} and J. Adam and G. Agakishiev and I. Aggarwal and Aggarwal, \{M. M.\} and Z. Ahammed and A. Aitbayev and I. Alekseev and E. Alpatov and Alshammri, \{A. K.\} and A. Aparin and S. Aslam and J. Atchison and Averichev, \{G. S.\} and V. Bairathi and X. Bao and P. Barik and K. Barish and S. Behera and P. Bhagat and A. Bhasin and S. Bhatta and Bordyuzhin, \{I. G.\} and Brandenburg, \{J. D.\} and Brandin, \{A. V.\} 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 Chang, \{Y. S.\} and Z. Chang and A. Chatterjee and D. Chen and Chen, \{J. H.\} and L. Chen and Q. Chen and W. Chen and Z. Chen and J. Cheng and Y. Cheng and W. Christie and X. Chu and S. Corey and Crawford, \{H. J.\} and A. Deshpande and J. Jia and R. Lacey",

note = "Publisher Copyright: {\textcopyright} 2026 The Authors.",

year = "2026",

month = apr,

doi = "10.1016/j.physletb.2026.140353",

language = "English",

volume = "875",

journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",

issn = "0370-2693",

}

TY - JOUR

T1 - Measurement of kaon directed flow in Au+Au collisions in the high baryon density region

AU - [email protected] STAR Collaboration

AU - Aboona, B. E.

AU - Adam, J.

AU - Agakishiev, G.

AU - Aggarwal, I.

AU - Aggarwal, M. M.

AU - Ahammed, Z.

AU - Aitbayev, A.

AU - Alekseev, I.

AU - Alpatov, E.

AU - Alshammri, A. K.

AU - Aparin, A.

AU - Aslam, S.

AU - Atchison, J.

AU - Averichev, G. S.

AU - Bairathi, V.

AU - Bao, X.

AU - Barik, P.

AU - Barish, K.

AU - Behera, S.

AU - Bhagat, P.

AU - Bhasin, A.

AU - Bhatta, S.

AU - Bordyuzhin, I. G.

AU - Brandenburg, J. D.

AU - Brandin, A. V.

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 - Chang, Y. S.

AU - Chang, Z.

AU - Chatterjee, A.

AU - Chen, D.

AU - Chen, J. H.

AU - Chen, L.

AU - Chen, Q.

AU - Chen, W.

AU - Chen, Z.

AU - Cheng, J.

AU - Cheng, Y.

AU - Christie, W.

AU - Chu, X.

AU - Corey, S.

AU - Crawford, H. J.

AU - Deshpande, A.

AU - Jia, J.

AU - Lacey, R.

PY - 2026/4

Y1 - 2026/4

N2 - Rapidity-odd directed flow v 1 measurements are presented for K ± and KS0 in Au + Au collisions for sNN from 3.0 to 3.9 GeV with the STAR experiment. For comparison, v 1 of π ± , protons, and Λ from the same collisions are also discussed. The mid-rapidity v 1 slope dv1/dy|y=0 for protons and Λ is positive in these collisions. On the other hand, v 1 slope of kaons exhibits a strong pT dependence: negative at pT< 0.6 GeV/ c and positive at higher pT. A similar pT dependence is also evident for the v 1 slope of charged pions. Compared to the spectator-removed calculations in Au+Au collisions at sNN= 3.0–3.9 GeV, the JAM model demonstrates a pronounced shift of the v 1 slopes of mesons towards the negative direction. It suggests that the shadowing effect of the spectators plays an important role in the observed kaon anti-flow at low pT in the high baryon density region of non-central collisions.

AB - Rapidity-odd directed flow v 1 measurements are presented for K ± and KS0 in Au + Au collisions for sNN from 3.0 to 3.9 GeV with the STAR experiment. For comparison, v 1 of π ± , protons, and Λ from the same collisions are also discussed. The mid-rapidity v 1 slope dv1/dy|y=0 for protons and Λ is positive in these collisions. On the other hand, v 1 slope of kaons exhibits a strong pT dependence: negative at pT< 0.6 GeV/ c and positive at higher pT. A similar pT dependence is also evident for the v 1 slope of charged pions. Compared to the spectator-removed calculations in Au+Au collisions at sNN= 3.0–3.9 GeV, the JAM model demonstrates a pronounced shift of the v 1 slopes of mesons towards the negative direction. It suggests that the shadowing effect of the spectators plays an important role in the observed kaon anti-flow at low pT in the high baryon density region of non-central collisions.

KW - Directed flow

KW - Heavy-ion collisions

KW - High baryon density region

KW - Kaon potential

KW - QCD phase structure

KW - Spectator effect

UR - https://www.scopus.com/pages/publications/105035507369

U2 - 10.1016/j.physletb.2026.140353

DO - 10.1016/j.physletb.2026.140353

M3 - Article

AN - SCOPUS:105035507369

SN - 0370-2693

VL - 875

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

M1 - 140353

ER -

Measurement of kaon directed flow in Au+Au collisions in the high baryon density region

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Keywords

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