ИСТИНА

Elliptic 𝜀2 and triangular 𝜀3 eccentricities arising in initial state of relativistic heavy-ion collisions are studied within the framework of a geometrical model with event-by-event fluctuations. Elliptic eccentricity is shown to be determined mainly by the average collision geometry, whereas the triangular one is related merely to the fluctuations. Assuming the linear dependence of the second 𝑣2, and third, 𝑣3, harmonics of anisotropic flow on 𝜀2 and 𝜀3, respectively, the model provides a fair description of the ALICE results for Pb+Pb collisions at √s_NN=5.02 TeV. Similar to spatial eccentricities, elliptic flow weakly depends on the fluctuations everywhere but in very central collisions, while triangular flow is mostly determined by the event-by-event fluctuations. For the collisions with centrality 0-2\% a novel scaling dependence for the magnitudes of the flow harmonics 𝑣𝑛 on atomic number 𝐴, 𝑣_𝑛∝𝐴−1/3, is predicted. This prediction agrees well with the available experimental data.