In this work Paul Sorensen has analyzed the production of mesons and baryons in heavy-ion collisions at Brookhaven's Relativistic Heavy Ion Collider (RHIC). In 2005, physicists at RHIC created the most perfect fluid in nature, called quark-gluon plasma, a hot, dense matter formed out of quarks and gluons that permeated the universe one microsecond after its birth. Sorensen's work plays a key role in elucidating that the flow of matter in the heavy-ion collisions is dominated by subatomic particles called quarks, indicating that quark-gluon plasma had been created. Sorensen's work helped discover quark number scaling in the elliptic flow of hadrons in nucleus-nucleus collisions, and he develops the interpretation showing the relevance of quark degrees of freedom in heavy ion interactions.