Abstract
The hot nuclear matter created at the Relativistic Heavy Ion Collider has been characterized by near-perfect fluid behavior. We demonstrate that this stands in contradiction to the identification of quantum chromodynamics quasiparticles with the thermodynamic degrees of freedom in the early (fluid) stage of heavy-ion collisions. The empirical observation of constituent quark ``${n}_{q}$'' scaling of elliptic flow [PHENIX, A. Adare et al., Phys. Rev. Lett. 98, 162301 (2007)] is juxtaposed with the lack of such scaling behavior in hydrodynamic fluid calculations followed by Cooper-Frye freeze-out to hadrons. As the hydrodynamic fluid expands, increasing viscous effects may allow for a short time period of ``quasiparticle transport'' prior to hadronization. However, without a detailed understanding of the transitions between these time stages, the ``${n}_{q}$'' scaling is not a necessary consequence of this prescription. Also, if the duration of this stage is too short, it may not support well-defined quasiparticles. By comparing and contrasting the coalescence of quarks into hadrons with the similar process of producing light nuclei from nucleons, it is shown that the observation of ``${n}_{q}$'' scaling in the final state does not necessarily imply that the constituent degrees of freedom were the relevant ones in the initial state.
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