Speaker
Koichi Murase
(The University of Tokyo)
Description
To investigate the physics of the strongly interacting system of quarks
and gluons under extreme conditions, heavy-ion collision experiments are
performed at Large Hadron Collider (LHC) and Relativistic Heavy Ion
Collider (RHIC). One of the major discoveries is that elliptic flow v_2
was comparable with an ideal hydrodynamic prediction and, as a result,
that a new paradigm of strongly coupled quark-gluon plasma (QGP) at
temperature of a few hundreds MeV was established. Recently, the higher
harmonics v_n (n > 2) are observed at RHIC and LHC and attract a lot of
theoretical and experimental interests. Initial condition with
fluctuation from initial nucleon distribution in colliding nuclei is
attributed to one of the major origins of the higher harmonics.
To understand detailed mechanism of how the higher harmonics develop, we
construct an integrated dynamical framework based on relativistic
hydrodynamics [1] and perform massive numerical simulations (10^5
minimum bias events) on an event-by-event basis [2]. In this framework,
the Monte-Carlo versions of factorized Kharzeev-Levin-Nardi (fKLN) model
(MC-KLN) and Glauber model (MC-Glauber) are employed as the
initialization models. After describing hydrodynamic evolution of the
matter using fully (3+1) dimensional ideal hydrodynamics, we treat the
subsequent dynamics of hadron gas using a hadron cascade model, JAM.
Using the obtained momentum distribution of the final hadrons, we
finally analyze the harmonics v_n in a way that experimental people
perform the flow analysis such as event plane method, multi-particle
cumulant method. We compare these results with the conventional
theoretically-obtained harmonics with respect to reaction plane or
participant plane to investigate the systematic uncertainty in the
conventional theoretical results. We found that v_n obtained in this way
depends on the flow analysis model, which means the importance of
consistent comparison between theoretical results with experimental
data. We also calculate v_n as a function of centrality using the MC-KLN
and MC-Glauber initialization and found differences of v_2, v_4 and v_5
between these two models. This indicates the simultaneous analysis of
several harmonics would discriminate between the initialization models.
[1] T. Hirano and Y. Nara, ``Dynamical modeling of high energy heavy ion
collisions,'' arXiv:1203.4418 [nucl-th].
[2] T. Hirano, P. Huovinen, K. Murase and Y. Nara, in preparation.
Author
Koichi Murase
(The University of Tokyo)
Co-authors
Pasi Huovinen
(Johann Wolfgang Goethe-Universität)
Tetsufumi Hirano
(Sophia Univ)
Yasushi Nara
(Akita International University)
