Observation of flow vector fluctuations in p–Pb collisions at √sNN = 5.02TeV

The ALICE collaboration

doi:10.1007/JHEP06(2026)152

Observation of flow vector fluctuations in p–Pb collisions at √sNN = 5.02TeV

The ALICE collaboration

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Wayne State University
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National Institute for Nuclear Physics
Variable Energy Cyclotron Centre India
Aligarh Muslim University
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National Research and Innovation Agency Republic of Indonesia
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GSI Helmholtz Centre for Heavy Ion Research
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Research output: Contribution to journal › Journal article › peer-review

Abstract

Measurements of transverse momentum (p_T) and pseudorapidity (η) dependent flow vector fluctuations in p–Pb collisions at TeV at the CERN Large Hadron Collider are presented. By studying long-range two-particle correlations with a template fit method, potential biases from non-flow effects such as jets and resonance decays are effectively suppressed. Significant p_T- and η-dependent fluctuations of the second-harmonic flow vector are observed with more than 5σ confidence in p–Pb collisions, similar to the observations in Pb–Pb collisions. The influence of residual non-flow effects has been evaluated and cannot account for the observed fluctuations, thereby confirming the observation of flow vector fluctuations in small collision systems at the LHC. Comparisons to model calculations from 3DGlauber+MUSIC+UrQMD and the parton transport model from AMPT are also presented. The measurements provide constraints on the theoretical modelling of the three-dimensional initial geometry and its event-by-event fluctuations, offering critical insights into the origin of collective flow in small collision systems at the LHC.

Original language	English
Article number	152
Journal	Journal of High Energy Physics
Volume	2026
Issue number	6
DOIs	https://doi.org/10.1007/JHEP06(2026)152
State	Published - 2026.06

Keywords

Heavy Ion Experiments
Particle Correlations and Fluctuations
Relativistic Heavy Ion Physics

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10.1007/JHEP06(2026)152

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@article{b2c109472c7d4dff9f6a9677c1cd34c2,

title = "Observation of flow vector fluctuations in p{\textendash}Pb collisions at √sNN = 5.02TeV",

abstract = "Measurements of transverse momentum (pT) and pseudorapidity (η) dependent flow vector fluctuations in p{\textendash}Pb collisions at TeV at the CERN Large Hadron Collider are presented. By studying long-range two-particle correlations with a template fit method, potential biases from non-flow effects such as jets and resonance decays are effectively suppressed. Significant pT- and η-dependent fluctuations of the second-harmonic flow vector are observed with more than 5σ confidence in p{\textendash}Pb collisions, similar to the observations in Pb{\textendash}Pb collisions. The influence of residual non-flow effects has been evaluated and cannot account for the observed fluctuations, thereby confirming the observation of flow vector fluctuations in small collision systems at the LHC. Comparisons to model calculations from 3DGlauber+MUSIC+UrQMD and the parton transport model from AMPT are also presented. The measurements provide constraints on the theoretical modelling of the three-dimensional initial geometry and its event-by-event fluctuations, offering critical insights into the origin of collective flow in small collision systems at the LHC.",

keywords = "Heavy Ion Experiments, Particle Correlations and Fluctuations, Relativistic Heavy Ion Physics",

author = "\{The ALICE collaboration\} and Abdallah, \{D. A.H.\} and Abualrob, \{I. J.\} and S. Acharya and \{Aglieri Rinella\}, G. and L. Aglietta and N. Agrawal and Z. Ahammed and S. Ahmad and I. Ahuja and Z. Akbar and V. Akishina and M. Al-Turany and B. Alessandro and \{Alfaro Molina\}, R. and B. Ali and A. Alici and J. Alme and G. Alocco and T. Alt and I. Altsybeev and C. Andrei and N. Andreou and A. Andronic and M. Angeletti and V. Anguelov and F. Antinori and P. Antonioli and N. Apadula and H. Appelsh{\"a}user and S. Arcelli and R. Arnaldi and Arsene, \{I. C.\} and M. Arslandok and A. Augustinus and R. Averbeck and Azmi, \{M. D.\} and H. Baba and Babu, \{A. R.J.\} and A. Badal{\`a} and J. Bae and Y. Bae and Baek, \{Y. W.\} and X. Bai and R. Bailhache and Y. Bailung and R. Bala and A. Baldisseri and B. Balis and S. Bangalia and Kim, \{E. J.\}",

note = "Publisher Copyright: {\textcopyright} The Author(s) 2026.",

year = "2026",

month = jun,

doi = "10.1007/JHEP06(2026)152",

language = "English",

volume = "2026",

journal = "Journal of High Energy Physics",

issn = "1029-8479",

number = "6",

}

TY - JOUR

T1 - Observation of flow vector fluctuations in p–Pb collisions at √sNN = 5.02TeV

AU - The ALICE collaboration

AU - Abdallah, D. A.H.

AU - Abualrob, I. J.

AU - Acharya, S.

AU - Aglieri Rinella, G.

AU - Aglietta, L.

AU - Agrawal, N.

AU - Ahammed, Z.

AU - Ahmad, S.

AU - Ahuja, I.

AU - Akbar, Z.

AU - Akishina, V.

AU - Al-Turany, M.

AU - Alessandro, B.

AU - Alfaro Molina, R.

AU - Ali, B.

AU - Alici, A.

AU - Alme, J.

AU - Alocco, G.

AU - Alt, T.

AU - Altsybeev, I.

AU - Andrei, C.

AU - Andreou, N.

AU - Andronic, A.

AU - Angeletti, M.

AU - Anguelov, V.

AU - Antinori, F.

AU - Antonioli, P.

AU - Apadula, N.

AU - Appelshäuser, H.

AU - Arcelli, S.

AU - Arnaldi, R.

AU - Arsene, I. C.

AU - Arslandok, M.

AU - Augustinus, A.

AU - Averbeck, R.

AU - Azmi, M. D.

AU - Baba, H.

AU - Babu, A. R.J.

AU - Badalà, A.

AU - Bae, J.

AU - Bae, Y.

AU - Baek, Y. W.

AU - Bai, X.

AU - Bailhache, R.

AU - Bailung, Y.

AU - Bala, R.

AU - Baldisseri, A.

AU - Balis, B.

AU - Bangalia, S.

AU - Kim, E. J.

PY - 2026/6

Y1 - 2026/6

N2 - Measurements of transverse momentum (pT) and pseudorapidity (η) dependent flow vector fluctuations in p–Pb collisions at TeV at the CERN Large Hadron Collider are presented. By studying long-range two-particle correlations with a template fit method, potential biases from non-flow effects such as jets and resonance decays are effectively suppressed. Significant pT- and η-dependent fluctuations of the second-harmonic flow vector are observed with more than 5σ confidence in p–Pb collisions, similar to the observations in Pb–Pb collisions. The influence of residual non-flow effects has been evaluated and cannot account for the observed fluctuations, thereby confirming the observation of flow vector fluctuations in small collision systems at the LHC. Comparisons to model calculations from 3DGlauber+MUSIC+UrQMD and the parton transport model from AMPT are also presented. The measurements provide constraints on the theoretical modelling of the three-dimensional initial geometry and its event-by-event fluctuations, offering critical insights into the origin of collective flow in small collision systems at the LHC.

AB - Measurements of transverse momentum (pT) and pseudorapidity (η) dependent flow vector fluctuations in p–Pb collisions at TeV at the CERN Large Hadron Collider are presented. By studying long-range two-particle correlations with a template fit method, potential biases from non-flow effects such as jets and resonance decays are effectively suppressed. Significant pT- and η-dependent fluctuations of the second-harmonic flow vector are observed with more than 5σ confidence in p–Pb collisions, similar to the observations in Pb–Pb collisions. The influence of residual non-flow effects has been evaluated and cannot account for the observed fluctuations, thereby confirming the observation of flow vector fluctuations in small collision systems at the LHC. Comparisons to model calculations from 3DGlauber+MUSIC+UrQMD and the parton transport model from AMPT are also presented. The measurements provide constraints on the theoretical modelling of the three-dimensional initial geometry and its event-by-event fluctuations, offering critical insights into the origin of collective flow in small collision systems at the LHC.

KW - Heavy Ion Experiments

KW - Particle Correlations and Fluctuations

KW - Relativistic Heavy Ion Physics

UR - https://www.scopus.com/pages/publications/105042604366

U2 - 10.1007/JHEP06(2026)152

DO - 10.1007/JHEP06(2026)152

M3 - Journal article

AN - SCOPUS:105042604366

SN - 1029-8479

VL - 2026

JO - Journal of High Energy Physics

JF - Journal of High Energy Physics

IS - 6

M1 - 152

ER -

Observation of flow vector fluctuations in p–Pb collisions at √sNN = 5.02TeV

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