Two-particle azimuthal correlations have been measured in neutral current deep inelastic ep scattering with virtuality Q2> 5 GeV2 at a centre-of-mass energy s = 318 GeV recorded with the ZEUS detector at HERA. The correlations of charged particles have been measured in the range of laboratory pseudorapidity −1.5 < η < 2.0 and transverse momentum 0.1 < pT< 5.0 GeV and event multiplicities Nch up to six times larger than the average 〈Nch〉 ≈ 5. The two-particle correlations have been measured in terms of the angular observables cn{2} = 〈〈cosnΔφ〉〉, where n is between 1 and 4 and ∆φ is the relative azimuthal angle between the two particles. Comparisons with available models of deep inelastic scattering, which are tuned to reproduce inclusive particle production, suggest that the measured two-particle correlations are dominated by contributions from multijet production. The correlations observed here do not indicate the kind of collective behaviour recently observed at the highest RHIC and LHC energies in high-multiplicity hadronic collisions.

Original languageEnglish
Article number70
JournalJournal of High Energy Physics
Issue number4
StatePublished - 1 Apr 2020


FundersFunder number
Creative Commons Attribution License
Department of Physics
INFN Bologna
INFN Padova, Padova, Italy, Dipartimento di Fisica e Astronomia dell’ Università
Italian National Institute for Nuclear Physics
Jagellonian University, Krakow, Poland
Kobe University
National Centre for Particle Physics50603
Physikalisches Institut der Universität Bonn
Heidelberg University 
Polish National Science Centre
Tokyo Institute of Technology, Tokyo, Japan)
Università di Torino
U.S. Department of Energy
Nuclear Physics
Natural Sciences and Engineering Research Council of Canada
York University
Science and Technology Facilities Council
Deutsches Elektronen-Synchrotron
Deutsche ForschungsgemeinschaftSFB 1225
Deutsche Forschungsgemeinschaft
Heidelberg University 
Ministry of Education, Culture, Sports, Science and Technology
Bundesministerium für Bildung und Forschung05h09GUF, 05 H09PDF, SFB 676
Bundesministerium für Bildung und Forschung
Ministry of Higher Education, Malaysia
Israel Science Foundation
Instituto Nazionale di Fisica Nucleare
Narodowe Centrum NaukiDEC-2014/13/B/ST2/02486
Narodowe Centrum Nauki
Tel Aviv University
Universiti MalayaER004-2012A
Universiti Malaya
GSI Helmholtzzentrum für Schwerionenforschung


    • Collective flow
    • Lepton-Nucleon Scattering (experiments)
    • Particle correlations and fluctuations
    • Quark gluon plasma


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