Observation of Long-Range Collective Flow in O+O and Ne+Ne Collisions and Implications for Nuclear Structure Studies

Abstract

The long-range collective flow of particles produced in oxygen-oxygen (O+O) and neon-neon (Ne+Ne) collisions is measured with the CMS detector at the CERN LHC. The data samples were collected at a center-of-mass energy per nucleon pair of 5.36 TeV, with integrated luminosities of 7 nb−1 and 0.8 nb−1 for O+O and Ne+Ne collisions, respectively. Two- and four-particle azimuthal correlations are measured over nearly five units of pseudorapidity. Significant elliptic (𝑣2) and triangular (𝑣3) flow harmonics are observed in both systems. The ratios of 𝑣𝑛 coefficients between Ne+Ne and O+O collisions suggest sensitivity to the intrinsic nuclear structure of the respective Ne and O ions. Hydrodynamic models with ab initio nuclear structure inputs qualitatively reproduce the collision-overlap dependence of both the 𝑣𝑛 values and the Ne+Ne to O+O ratios. These measurements provide new constraints when modeling the interplay of nuclear structure and collective dynamics in collisions of 16O and 20Ne ions, respectively.