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Two-particle azimuthal correlations as a probe of collective behaviour in deep inelastic ep scattering at HERA

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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 \( \sqrt{s} \) = 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.


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ArXiv ePrint: 1912.07431

Supported by the Italian National Institute for Nuclear Physics (INFN) (INFN Bologna, Bologna, Italy, Calabria University, Physics Department and INFN, Cosenza, Italy, INFN Padova, Padova, Italy, Dipartimento di Fisica e Astronomia dell’ Università and INFN, Padova, Italy, Università di Torino and INFN, Torino, Italy, Università del Piemonte Orientale, Novara, and INFN, Torino, Italy)

Supported by the German Federal Ministry for Education and Research (BMBF), under contract No. 05 H09PDF (Physikalisches Institut der Universität Bonn, Bonn, Germany)

Supported by HIR grant UM.C/625/1/HIR/149 and UMRG grants RU006-2013, RP012A-13AFR and RP012B-13AFR from Universiti Malaya, and ERGS grant ER004-2012A from the Ministry of Education, Malaysia (National Centre for Particle Physics, Universiti Malaya, 50603 Kuala Lumpur, Malaysia)

Supported by the Polish National Science Centre (NCN) grant no. DEC-2014/13/B/ST2/02486 (Department of Physics, Jagellonian University, Krakow, Poland)

Supported by the Science and Technology Facilities Council, U.K. (School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom, Department of Physics, University of Oxford, Oxford, United Kingdom, Physics and Astronomy Department, University College London, London, United Kingdom)

Supported by the German Federal Ministry for Education and Research (BMBF), under contract No. 05h09GUF, and the SFB 676 of the Deutsche Forschungsgemeinschaft (DFG) (Hamburg University, Institute of Experimental Physics, Hamburg, Germany)

Supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and its grants for Scientific Research (Institute of Particle and Nuclear Studies, KEK, Tsukuba, Japan, Department of Physics, Kobe University, Kobe, Japan, Department of Physics, Tokyo Institute of Technology, Tokyo, Japan)

Supported by the Israel Science Foundation (Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics, Tel Aviv University, Tel Aviv, Israel)

Supported in part by the Office of Nuclear Physics within the U.S. DOE Office of Science (Department of Physics, Temple University, Philadelphia, PA 19122, U.S.A.)

Supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) (Department of Physics, York University, Ontario, Canada M3J 1P3)

This work is part of and supported by the DFG Collaborative Research Centre “SFB 1225 (ISOQUANT)” (GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany, Physikalisches Institute, University of Heidelberg, Heidelberg, Germany, Institute for Theoretical Physics, University of Heidelberg, Heidelberg, Germany)

Supported by DESY (M. Wing)

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The ZEUS collaboration., Abt, I., Adamczyk, L. et al. Two-particle azimuthal correlations as a probe of collective behaviour in deep inelastic ep scattering at HERA. J. High Energ. Phys. 2020, 70 (2020).

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