Speaker
Dr
shengli huang
(PHENIX Collaboration)
Description
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)
Peer reviewing
Paper
Paper files:
