2-particle correlation analysis with Spherical Harmonics

The collective behavior of particles created in high-energy collisions is typically studied using azimuthal asymmetries between different particles or the reaction plane of the event. These correlations, expressed in Fourier compositions, have been measured by all RHIC and LHC experiments and studied in several hydrodynamics and other approaches. Recent observations of collectivity in small systems pose challenges on the true sources of the collectivity behavior. We propose the use of 3-D spherical harmonics to simultaneously quantify azimuthal and rapidity asymmetries in particle correlations, providing additional information on particle collectivity. This presentation is going to report how spherical harmonics respond to basic assumptions, such as single and double jets, event generators and some hydrodynamic models. We will also discuss the perspective to test particle collectivity models by measuring spherical harmonics in real data.