Speaker
Description
Understanding the onset of collective flow from small to large heavy ion collisions is crucial for the study of the smallest QGP droplet. As particle multiplicity decreases in smaller systems, flow signal becomes smaller and nonflow background is larger. The nonflow correlations can be significant even when imposing a large pseudorapidity gap between particles when using two-particle correlations in small systems. The experiments at the Large Hadron Collider have developed two methods for subtracting nonflow contribution in two-particle correlations. The methods have also been tested at the lower collision energy at the Relativistic Heavy Ion Collider. For multiparticle correlations, using multiple subevents has been shown to remove much more nonflow compared to the standard cumulant method in small systems. Directly looping over particle azimuthal angles could remove most of the nonflow when pseudorapidity gaps are applied between particles. I will review the nonflow subtraction techniques for both two particle and multiparticle correlation methods in this talk.
