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Anisotropic fluctuations of momentum and angular momentum of heavy quarks in the pre-equilibrium stage of pA collisions at the LHC

Gabriele Parisi1,2,*, Vincenzo Greco1,2,†, and Marco Ruggieri1,3,‡

  • *Contact author: gabriele.parisi@dfa.unict.it
  • †Contact author: vincenzo.greco@dfa.unict.it
  • ‡Contact author: marco.ruggieri@dfa.unict.it
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Phys. Rev. D 112, 074030 – Published 23 October, 2025

DOI: https://doi.org/10.1103/lvv6-xx41

Abstract

We simulate the real-time evolution of the SU(3)-glasma generated in the early stages of high-energy proton-nucleus collisions, employing classical lattice gauge theory techniques. Our setup incorporates a realistic modeling of the proton’s internal structure and includes longitudinal fluctuations in the initial state, enabling the study of genuinely nonboost-invariant collision dynamics. Focusing on the momentum and angular momentum anisotropies of heavy quarks in the infinite mass limit, we find that the system retains significant anisotropy well beyond the characteristic timescale τ=1/Qs, with Qs being the saturation energy of the glasma, the only scale in our model. This persistence of anisotropy is further confirmed in the more realistic, nonboost-invariant scenario, across a range of fluctuation amplitudes. These findings pave the way for future investigations involving dynamical heavy quarks and more quantitative initializations of the glasma.

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Phys. Rev. D 112, 074030– Published 23 October, 2025
  • Received 3 June 2025
  • Revised 18 September 2025
  • Accepted 7 October 2025
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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. Funded by SCOAP3.

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