Quasiparticle degrees of freedom versus the perfect fluid as descriptors of the quark-gluon plasma
- University of Colorado, Boulder (United States)
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{sub 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{sub 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{sub q}' scaling in the final state does not necessarily imply that the constituent degrees of freedom were the relevant ones in the initial state.
- OSTI ID:
- 21192334
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 78, Issue 4; Other Information: DOI: 10.1103/PhysRevC.78.044905; (c) 2008 The Avarican Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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