- Physical Review Journals
All JournalsPhysics Magazine

Physical Review D

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Open Access

Investigating the broadening phenomenon in two-particle correlations induced by gluon saturation

K. Cassar1,*, Z. Wang2,†, X. Chu3,‡, and E. C. Aschenauer3,§

  • 1Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
  • 2Institute of Frontier and Interdisciplinary Science and Key Laboratory of Particle Physics and Particle Irradiation (Ministry of Education), Shandong University, Qingdao, Shandong, 266237, China
  • 3Physics Department, Brookhaven National Laboratory, Upton, New York 11973, USA

  • *Contact author: kiera.g.cassar@gmail.com
  • †Contact author: wang.zhen@sdu.edu.cn
  • ‡Contact author: xchu@bnl.gov
  • §Contact author: elke@bnl.gov
PDF

Phys. Rev. D 112, 034034 – Published 27 August, 2025

DOI: https://doi.org/10.1103/7jxl-8pzn

Abstract

It has been found that the gluon density inside the proton grows rapidly at small momentum fractions. Quantum chromodynamics (QCD) predicts that this growth can be regulated by nonlinear effects, ultimately leading to gluon saturation. Within the color glass condensate framework, nonlinear QCD effects are predicted to suppress and broaden back-to-back angular correlations in collisions involving heavy nuclei. While suppression has been observed in various experiments in d/p+A collisions compared to p+p collisions, the predicted broadening remains unobserved. This study investigates the contributions of intrinsic transverse momentum (kT), which is associated with saturation physics, as well as parton showers and transverse motion from fragmentation (pTfrag), which are not saturation dependent, to the width of the correlation function. Our findings show that the non-saturation dependent effects, especially the initial-state parton shower and pTfrag, which occur independently of the collision system, smear the back-to-back correlation more than gluon saturation does, making the broadening phenomenon difficult to observe.

View figure in article

Physics Subject Headings (PhySH)

Article Text

References (57)

  1. H. Abramowicz et al. (H1, ZEUS Collaborations), Eur. Phys. J. C 75, 580 (2015).
  2. L. V. Gribov, E. M. Levin, and M. G. Ryskin, Phys. Rep. 100, 1 (1983).
  3. N. Armesto, C. A. Salgado, and U. A. Wiedemann, Phys. Rev. Lett. 94, 022002 (2005).
  4. F. Gelis, E. Iancu, J. Jalilian-Marian, and R. Venugopalan, Annu. Rev. Nucl. Part. Sci. 60, 463 (2010).
  5. J. L. Albacete and C. Marquet, Phys. Rev. Lett. 105, 162301 (2010).
  6. K. Tuchin, Nucl. Phys. A846, 83 (2010).
  7. Y. V. Kovchegov and E. Levin, Quantum Chromodynamics at High Energy (Cambridge University Press, Cambridge, England, 2012), Vol. 33.
  8. J. Albacete and C. Marquet, Prog. Part. Nucl. Phys. 76, 1 (2014).
  9. A. Morreale and F. Salazar, Universe 7, 312 (2021).
  10. V. N. Gribov and L. N. Lipatov, Sov. J. Nucl. Phys. 15, 438 (1972).
  11. Y. L. Dokshitzer, Sov. Phys. JETP 46, 641 (1977), http://www.jetp.ras.ru/cgi-bin/dn/e_046_04_0641.pdf.
  12. N. N. K. Borah, D. K. Choudhury, and P. K. Sahariah, Pramana 79, 833 (2012).
  13. F. D. Aaron et al. (H1, ZEUS Collaborations), J. High Energy Phys. 01 (2010) 109.
  14. E. Iancu and R. Venugopalan, The color glass condensate and high-energy scattering in QCD, in Quark-Gluon Plasma 4, edited by R. C. Hwa and X.-N. Wang (World Scientific, Singapore, 2004), pp. 249–3363.
  15. L. V. Gribov, E. M. Levin, and M. G. Ryskin, Phys. Rep. 100, 1 (1983).
  16. A. H. Mueller and J.-w. Qiu, Nucl. Phys. B268, 427 (1986).
  17. R. C. Hwa, C. B. Yang, and R. J. Fries, Phys. Rev. C 71, 024902 (2005).
  18. I. Balitsky, Nucl. Phys. B463, 99 (1996).
  19. Y. V. Kovchegov, Phys. Rev. D 60, 034008 (1999).
  20. J. Jalilian-Marian, A. Kovner, L. D. McLerran, and H. Weigert, Phys. Rev. D 55, 5414 (1997).
  21. H. Weigert, Nucl. Phys. A703, 823 (2002).
  22. E. Iancu, A. Leonidov, and L. D. McLerran, Phys. Lett. B 510, 133 (2001).
  23. C. Marquet, Nucl. Phys. A796, 41 (2007).
  24. L. Zheng, E. C. Aschenauer, J. H. Lee, and B.-W. Xiao, Phys. Rev. D 89, 074037 (2014).
  25. L. D. McLerran and R. Venugopalan, Phys. Rev. D 49, 2233 (1994).
  26. L. D. McLerran and R. Venugopalan, Phys. Rev. D 49, 3352 (1994).
  27. E. Iancu, A. Leonidov, and L. McLerran, in QCD Perspectives on Hot and Dense Matter (Springer, New York, 2002), pp. 73–145.
  28. V. Guzey, M. Strikman, and W. Vogelsang, Phys. Lett. B 603, 173 (2004).
  29. D. Kharzeev, E. Levin, and L. McLerran, Nucl. Phys. A748, 627 (2005).
  30. C. Marquet, Nucl. Phys. A796, 41 (2007).
  31. I. Arsene et al. (BRAHMS Collaboration), Phys. Rev. Lett. 91, 072305 (2003).
  32. I. Arsene et al. (BRAHMS Collaboration), Phys. Rev. Lett. 93, 242303 (2004).
  33. S. S. Adler et al. (PHENIX Collaboration), Phys. Rev. Lett. 94, 082302 (2005).
  34. S. S. Adler et al. (PHENIX Collaboration), Phys. Rev. Lett. 96, 222301 (2006).
  35. J. Adams et al. (STAR Collaboration), Phys. Rev. Lett. 97, 152302 (2006).
  36. R. Aaij et al. (LHCb Collaboration), J. High Energy Phys. 10 (2017) 090.
  37. R. Aaij et al. (LHCb Collaboration), J. High Energy Phys. 01 (2024) 070.
  38. A. Adare et al. (PHENIX Collaboration), Phys. Rev. Lett. 107, 172301 (2011).
  39. M. S. Abdallah et al. (STAR Collaboration), Phys. Rev. Lett. 129, 092501 (2022).
  40. R. Aaij et al. (LHCb Collaboration), Phys. Lett. B 762, 473 (2016).
  41. M. Aaboud et al. (ATLAS Collaboration), Phys. Rev. C 100, 034903 (2019).
  42. A. H. Mueller, B.-W. Xiao, and F. Yuan, Phys. Rev. Lett. 110, 082301 (2013).
  43. A. H. Mueller, B.-W. Xiao, and F. Yuan, Phys. Rev. D 88, 114010 (2013).
  44. P. Caucal, F. Salazar, B. Schenke, T. Stebel, and R. Venugopalan, Phys. Rev. Lett. 132, 081902 (2024).
  45. J. L. Albacete, G. Giacalone, C. Marquet, and M. Matas, Phys. Rev. D 99, 014002 (2019).
  46. D. V. Perepelitsa, Phys. Rev. C 111, 054901 (2025).
  47. T. Lappi and H. Mäntysaari, Phys. Rev. D 88, 114020 (2013).

  48. In pythia, kx and ky are assigned independently from Gaussian distributions with the same width, since pythia allows only a single parameter to control the transverse momentum spread. The resulting magnitude of kT, |kT|=kx2+ky2, then follows a Rayleigh distribution, whose central value corresponds to the Gaussian width.

  49. M. Anselmino, M. Boglione, J. O. Gonzalez Hernandez, S. Melis, and A. Prokudin, J. High Energy Phys. 04 (2014) 005.
  50. J. Ashman et al. (European Muon Collaboration), Z. Phys. C 52, 361 (1991).
  51. A. Airapetian et al. (HERMES Collaboration), Phys. Lett. B 684, 114 (2010).
  52. A. Airapetian et al. (HERMES Collaboration), Phys. Rev. D 87, 074029 (2013).
  53. C. Adolph et al. (COMPASS Collaboration), Eur. Phys. J. C 73, 2531 (2013); 75, 94(E) (2015).
  54. T. Sjostrand, S. Mrenna, and P. Z. Skands, J. High Energy Phys. 05 (2006) 026.
  55. J. Adam et al. (STAR Collaboration), Phys. Rev. D 100, 052005 (2019).
  56. D. Bourilkov, R. C. Group, and M. R. Whalley, in TeV4LHC Workshop—4th Meeting (2006), arXiv:hep-ph/0605240.
  57. J. Pumplin, D. R. Stump, J. Huston, H. L. Lai, P. M. Nadolsky, and W. K. Tung, J. High Energy Phys. 07 (2002) 012.

Outline

Information

Phys. Rev. D 112, 034034– Published 27 August, 2025
  • Received 15 March 2025
  • Accepted 1 August 2025
Crossmark - Check for updates button
Creative Commons Logo

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. Funded by SCOAP3.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation