Evidence of Spin-Interference Effects in Exclusive J/ψ →e+e- Photoproduction in Ultraperipheral Heavy-Ion Collisions

STAR Collaboration

doi:10.1103/tcdb-ldh8

Evidence of Spin-Interference Effects in Exclusive J/ψ →e⁺e^- Photoproduction in Ultraperipheral Heavy-Ion Collisions

STAR Collaboration

Texas A and M University
Czech Technical University in Prague
Univ of Mining and Metallurgy
Panjab University
VECC Kolkata
Kent State University
Brookhaven National Laboratory
Fudan University
Abilene Christian University
Universidad de Tarapacá
Shandong University
Iiser Berhampur
University of California, Riverside
Iiser Tirupati
University of Houston
University of Jammu
SUNY
Nuclear Physics Institute of the Cas
Ohio State University
Shanghai Institute of Applied Physics, Chinese Academy of Sciences
Yale University
University of California, 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
University of California at Berkeley
Eotvos Lorand University (ELTE)
Heidelberg University
The American University in Cairo Cairo
Rice University
Tsukuba University
UIC ECE-CSN-Lab
University of Kentucky
Universite della Calabria
Southern Connecticut State University
Institute of Modern Physics Chinese Academy of Sciences
Technische Universität Darmstadt
Valparaiso University
Huzhou University
University of Chinese Academy of Sciences
Academica Sinica
National Cheng Kung University
University of Science and Technology of China
Sejong University
Wayne State University
Temple University
Warsaw Institute of Technology
Frankfurt Institute for Advanced Studies
Lehigh University
Wuhan University of Science and Technology
South China Normal University
Texas Southern University
University of Texas at Austin
National Institute of Science Education and Research
Lovely Professional University
Rutgers University–New Brunswick
Max-Planck-Institut für Physik
Creighton University
Iit Patna
Ball State University
Michigan State University
Argonne National Laboratory
United States Naval Academy
Chongqing University
Second Hospital of Lanzhou University

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

Abstract

We report the first evidence of spin interference in exclusive J/ψ→e⁺e^- photoproduction in ultraperipheral heavy-ion collisions at STAR at √s_NN=200 GeV. In Au+Au collisions, a negative cos(2φ) modulation is found for p_T<120 MeV/c with a significance of 3.2σ, while the isobar data (Ru+Ru, Zr+Zr) show a consistent negative modulation with a significance of 1.9σ, opposite in sign to that in ρ⁰→π⁺π^- photoproduction. This establishes for the first time that the interference sign is controlled by the spin structure of the final-state daughters, resolving the ambiguity present in the all-boson ρ⁰ channel. The compact J/ψ probes gluon distributions at perturbative scales, resulting in a weaker modulation and providing stringent constraints on color glass condensate calculations. These findings demonstrate that spin-dependent interference in heavy vector mesons provides a new, experimentally accessible handle on gluon structure beyond traditional cross-section measurements.

Original language	English
Article number	242302
Journal	Physical Review Letters
Volume	136
Issue number	24
DOIs	https://doi.org/10.1103/tcdb-ldh8
State	Published - 19 Jun 2026
Externally published	Yes

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10.1103/tcdb-ldh8

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@article{3fdd37a4c9df4a868d8af7b69ff5a7f6,

title = "Evidence of Spin-Interference Effects in Exclusive J/ψ →e+e- Photoproduction in Ultraperipheral Heavy-Ion Collisions",

abstract = "We report the first evidence of spin interference in exclusive J/ψ→e+e- photoproduction in ultraperipheral heavy-ion collisions at STAR at √sNN=200 GeV. In Au+Au collisions, a negative cos(2φ) modulation is found for pT<120 MeV/c with a significance of 3.2σ, while the isobar data (Ru+Ru, Zr+Zr) show a consistent negative modulation with a significance of 1.9σ, opposite in sign to that in ρ0→π+π- photoproduction. This establishes for the first time that the interference sign is controlled by the spin structure of the final-state daughters, resolving the ambiguity present in the all-boson ρ0 channel. The compact J/ψ probes gluon distributions at perturbative scales, resulting in a weaker modulation and providing stringent constraints on color glass condensate calculations. These findings demonstrate that spin-dependent interference in heavy vector mesons provides a new, experimentally accessible handle on gluon structure beyond traditional cross-section measurements.",

author = "\{STAR Collaboration\} and 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 P. Barik 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 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 M. Csan{\'a}d and G. Dale-Gau and A. Das and S. Paul",

note = "Publisher Copyright: {\textcopyright} 2026 American Physical Society.",

year = "2026",

month = jun,

day = "19",

doi = "10.1103/tcdb-ldh8",

language = "English",

volume = "136",

journal = "Physical Review Letters",

issn = "0031-9007",

publisher = "American Physical Society",

number = "24",

}

TY - JOUR

T1 - Evidence of Spin-Interference Effects in Exclusive J/ψ →e+e- Photoproduction in Ultraperipheral Heavy-Ion Collisions

AU - STAR Collaboration

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 - Barik, P.

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 - 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 - Csanád, M.

AU - Dale-Gau, G.

AU - Das, A.

AU - Paul, S.

PY - 2026/6/19

Y1 - 2026/6/19

N2 - We report the first evidence of spin interference in exclusive J/ψ→e+e- photoproduction in ultraperipheral heavy-ion collisions at STAR at √sNN=200 GeV. In Au+Au collisions, a negative cos(2φ) modulation is found for pT<120 MeV/c with a significance of 3.2σ, while the isobar data (Ru+Ru, Zr+Zr) show a consistent negative modulation with a significance of 1.9σ, opposite in sign to that in ρ0→π+π- photoproduction. This establishes for the first time that the interference sign is controlled by the spin structure of the final-state daughters, resolving the ambiguity present in the all-boson ρ0 channel. The compact J/ψ probes gluon distributions at perturbative scales, resulting in a weaker modulation and providing stringent constraints on color glass condensate calculations. These findings demonstrate that spin-dependent interference in heavy vector mesons provides a new, experimentally accessible handle on gluon structure beyond traditional cross-section measurements.

AB - We report the first evidence of spin interference in exclusive J/ψ→e+e- photoproduction in ultraperipheral heavy-ion collisions at STAR at √sNN=200 GeV. In Au+Au collisions, a negative cos(2φ) modulation is found for pT<120 MeV/c with a significance of 3.2σ, while the isobar data (Ru+Ru, Zr+Zr) show a consistent negative modulation with a significance of 1.9σ, opposite in sign to that in ρ0→π+π- photoproduction. This establishes for the first time that the interference sign is controlled by the spin structure of the final-state daughters, resolving the ambiguity present in the all-boson ρ0 channel. The compact J/ψ probes gluon distributions at perturbative scales, resulting in a weaker modulation and providing stringent constraints on color glass condensate calculations. These findings demonstrate that spin-dependent interference in heavy vector mesons provides a new, experimentally accessible handle on gluon structure beyond traditional cross-section measurements.

UR - https://www.scopus.com/pages/publications/105043788352

U2 - 10.1103/tcdb-ldh8

DO - 10.1103/tcdb-ldh8

M3 - Article

AN - SCOPUS:105043788352

SN - 0031-9007

VL - 136

JO - Physical Review Letters

JF - Physical Review Letters

IS - 24

M1 - 242302

ER -

Evidence of Spin-Interference Effects in Exclusive J/ψ →e⁺e^- Photoproduction in Ultraperipheral Heavy-Ion Collisions

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