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Exploring differential two-particle correlations in γp and low-multiplicity pp collisions using pythia8

Subash Chandra Behera1,* and Dukhishyam Mallick2,†

  • *Contact author: subash.chandra.behera@cern.ch
  • †Contact author: dukhishyam.mallick@cern.ch
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Phys. Rev. D 114, 076025 – Published 26 October, 2026

DOI: https://doi.org/10.1103/fq2g-2vz2

Abstract

A study of two-particle differential number (B) and transverse momentum (P2CD) balance functions in photon-proton (γp) and proton-proton (pp) collisions at s=5.36  TeV is presented. The analysis focuses on inclusive charged hadrons within the pseudorapidity coverage |η|<2.4 and the transverse momentum interval 0.3<pT<3.0  GeV and examines their correlations in terms of relative pseudorapidity (Δη) and relative azimuthal angle (Δϕ). The correlation functions are evaluated for same- and opposite-sign pairs, and their combinations are used to extract charge-dependent (CD) and charge-independent (CI) components. The evolution of the nearside peak of the CD correlations is investigated in terms of Δη and Δϕ as a function of charged-particle multiplicity (Nch) for γp collisions and compared to pp collisions at a similar multiplicity range. A clear multiplicity dependence of the balance-function width is obtained. The width is found systematically lower in γp events than in pp collisions. This study provides valuable information on particle correlations and production mechanisms in low-Nch regimes for upcoming measurements in small systems.

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Phys. Rev. D 114, 076025– Published 26 October, 2026
  • Received 23 February 2026
  • Accepted 7 October 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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