This paper presents the first measurements of the azimuthal anisotropy coefficients 𝑣𝑛, which quantify the 𝑛⁢th-order Fourier modulation of charged-particle azimuthal distributions, for 𝑛=2−4 in √𝑠𝑁⁢𝑁=5.36TeV 16 O + 16 O and 20 Ne + 20 Ne collisions recorded with the ATLAS detector at the CERN Large Hadron Collider in 2025. The 𝑣𝑛 coefficients are measured as a function of transverse momentum (𝑝T), collision centrality, and event multiplicity. They are extracted using two complementary methods: two-particle correlations with a template-fit subtraction of short-range nonflow contributions, and four-particle subevent cumulants, which intrinsically suppress nonflow effects and provide sensitivity to flow fluctuations. The results show a clear hierarchy 𝑣2>𝑣3>𝑣4 and a nonmonotonic dependence on 𝑝T, reaching a maximum around 2GeV, consistent with trends observed in heavy-ion collisions. Detailed comparisons between the two collision systems reveal an enhanced 𝑣2 in central 20 Ne + 20 Ne collisions, consistent with theory expectations based on the predicted prolate deformation of neon nuclei, in contrast to the slightly tetrahedral structure predicted for oxygen. The four-particle cumulant results highlight strong event-by-event fluctuations and provide the greatest sensitivity to nuclear shape effects. These measurements can place new constraints on the initial geometry and the hydrodynamic response in light-ion collisions, offering valuable input for models of nuclear structure.

Aad, G., Aakvaag, E., Abbott, B., Abdelhameed, S., Abeling, K., Abicht, N.J., et al. (2025). Measurement of the azimuthal anisotropy of charged particles in √𝑠𝑁⁢𝑁=5.36TeV 16 O + 16 O and 20 Ne + 20 Ne collisions with the ATLAS detector. PHYSICAL REVIEW C, 113(4), 045205-1-045205-30 [10.1103/xqxz-8bhf].

Measurement of the azimuthal anisotropy of charged particles in √𝑠𝑁⁢𝑁=5.36TeV 16 O + 16 O and 20 Ne + 20 Ne collisions with the ATLAS detector

Alberghi, G. L.;Alfonsi, F.;Ballabene, E.;Bellagamba, L.;Bianco, G.;Boscherini, D.;Bruni, A.;Carratta, G.;Clissa, L.;Cremonini, D.;De Castro, S.;Fabbri, F.;Fabbri, L.;Franchini, M.;Gabrielli, A.;Giacobbe, B.;Lasagni Manghi, F.;Levrini, G.;Nechaeva, S.;Polini, A.;Rinaldi, L.;Romano, M.;Sanzani, E.;Sbarra, C.;Sbrizzi, A.;Semprini-Cesari, N.;Sioli, M.;Todome, K.;Valentinetti, S.;Villa, M.;Vittori, C.;Vivarelli, I.;Zoccoli, A.;
2025

Abstract

This paper presents the first measurements of the azimuthal anisotropy coefficients 𝑣𝑛, which quantify the 𝑛⁢th-order Fourier modulation of charged-particle azimuthal distributions, for 𝑛=2−4 in √𝑠𝑁⁢𝑁=5.36TeV 16 O + 16 O and 20 Ne + 20 Ne collisions recorded with the ATLAS detector at the CERN Large Hadron Collider in 2025. The 𝑣𝑛 coefficients are measured as a function of transverse momentum (𝑝T), collision centrality, and event multiplicity. They are extracted using two complementary methods: two-particle correlations with a template-fit subtraction of short-range nonflow contributions, and four-particle subevent cumulants, which intrinsically suppress nonflow effects and provide sensitivity to flow fluctuations. The results show a clear hierarchy 𝑣2>𝑣3>𝑣4 and a nonmonotonic dependence on 𝑝T, reaching a maximum around 2GeV, consistent with trends observed in heavy-ion collisions. Detailed comparisons between the two collision systems reveal an enhanced 𝑣2 in central 20 Ne + 20 Ne collisions, consistent with theory expectations based on the predicted prolate deformation of neon nuclei, in contrast to the slightly tetrahedral structure predicted for oxygen. The four-particle cumulant results highlight strong event-by-event fluctuations and provide the greatest sensitivity to nuclear shape effects. These measurements can place new constraints on the initial geometry and the hydrodynamic response in light-ion collisions, offering valuable input for models of nuclear structure.
2025
Aad, G., Aakvaag, E., Abbott, B., Abdelhameed, S., Abeling, K., Abicht, N.J., et al. (2025). Measurement of the azimuthal anisotropy of charged particles in √����⁢��=5.36TeV 16 O + 16 O and 20 Ne + 20 Ne collisions with the ATLAS detector. PHYSICAL REVIEW C, 113(4), 045205-1-045205-30 [10.1103/xqxz-8bhf].
Aad, G.; Aakvaag, E.; Abbott, B.; Abdelhameed, S.; Abeling, K.; Abicht, N. J.; Abidi, S. H.; Aboelela, M.; Aboulhorma, A.; Abramowicz, H.; Abulaiti, Y...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/1087065
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