Aug 12 – 18, 2012
US/Eastern timezone

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Deviation from quark number scaling of the anisotropy parameter v2 of pions, kaons, and protons in Au+Au collisions at 200 GeV

Aug 15, 2012, 11:00 AM
Regency 2/3

Regency 2/3


Dr shengli huang (PHENIX Collaboration)


The number of quark ($n_q$) scaling, which is manifested as $v^{hadron}_{2}(p_T) \approx n_q*v_2(p_T/n_q)$, is an approximate scaling that comes from the addition of the valence quark momenta at hadronization. The observation of $n_q$ scaling has been claimed that a partonic matter with quark-like degrees of freedom and significant collectivity has been generated in heavy ion collisions~\ref{1,2}. However, there are several theoretical considerations that suggest that the $n_q$ scaling should be violated in certain conditions. For example, the contribution of sea quarks and gluons have been shown to affect the $n_q$ scaling in the models including higher Fock states. And models that consider recombination between "thermal" and "shower" partons predict centrality dependent deviations from $n_q$ scaling. Understanding the limits of the recombination domain is important in relation to viscous hydrodynamics and the extraction of the shear viscosity over entropy density ($\eta/s$) from the data, as well as for developing a unified approach in describing jet energy loss and high $p_T$ $v_2$. Searches for deviations from $n_q$ scaling are also important for the low-energy scan program at RHIC as they have been considered as a signature of the transition between sQGP formation and a hadronic system. In this talk, we will report on high-statistics measurements of the second order Fourier coefficient $v_2$ for identified pions, kaons and protons, which extend to relatively high $p_T$ around 6 GeV/c. Comparisons with published measurements of $K^{0}_{S}$ and $\Lambda$ are shown for the different centralities. With these new measurements, the $p_T$ limits and centrality dependence of the $n_q$ scaling deviations are being carried out in PHENIX. [1]V. Greco, C. M. Ko, and P. Levai, Phys. Rev. Lett. 90, 42 202302 (2003). 43 [2] D. Molnar and S. A. Voloshin, Phys. Rev.Lett. 91, 44 092301 (2003).

Primary author

Dr shengli huang (PHENIX Collaboration)

Presentation materials

Peer reviewing