We demonstrate that the striking systematics of two-particle azimuthal Fourier harmonics $v_2$ and $v_3$ in ultrarelativistic collisions of protons, deuterons, and helium-3 ions off gold nuclei measured by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC) is reproduced in the color glass condensate effective field theory. This contradicts the claim in C. Aidala et al. (PHENIX Collaboration), arXiv:1805.02973, that their data rule out initial state-based explanations. The underlying systematics of the effect, as discussed previously in K. Dusling, M. Mace, R. Venugopalan, Phys. Rev. D 97, 016014 (2018); Phys. Rev. Lett. 120, 042002 (2018); Proc. Sci., QCDEV2017 (2018) 039, arise from the differing structure of strong color correlations between gluon domains of size $1/Q_S$ at fine ($p_{\perp }⪆Q_S$) or coarser ($p_{\perp }⪅Q_S$) transverse momentum resolution. Further tests of the limits of validity of this framework can be carried out in light-heavy ion collisions at both RHIC and the Large Hadron Collider. Such measurements also offer novel opportunities for further exploration of the role of the surprisingly large short-range nuclear correlations measured at Jefferson Lab.

• Received 4 June 2018

DOI:https://doi.org/10.1103/PhysRevLett.121.052301

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Published by the American Physical Society