65 research outputs found
Hydrodynamic Description of Heavy Ion Collisions
We give a short review of hydrodynamic models at heavy ion collisions from
the point of view of initial conditions, an equation of states (EoS) and
freezeout process. Then we show our latest results of a combined fully
three-dimensional macroscopic/microscopic transport approach. In this model for
the early, dense, deconfined stage relativistic 3D-hydrodynamics of the
reaction and a microscopic non-equilibrium model for the later hadronic stage
where the equilibrium assumptions are not valid anymore are employed. Within
this approach we study the dynamics of hot, bulk QCD matter, which is being
created in ultra-relativistic heavy ion collisions at RHIC.Comment: 8 pages, 9 figures, latex, plenary presentation at the 19th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(QM2006), Shanghai, China Nov. 14-20, 200
Analysis of the scalar mesons on the Lattice
We study the possibility that the scalar mesons exist as four-quark states.
The energy shift of two pseudoscalar mesons as a function of spatial lattice
size makes a distinction between bound states and scattering states of
four-quark states. We calculate the four-quark state in the quenched
approximation, ignoring the two-quark annihilation diagrams and the vacuum
channels. We perform a calculation of pseudoscalar meson scattering amplitudes,
using N_f=2 Wilson fermion and plaquette/Iwasaki gauge actions. We obtain the
indication that the four-quark states in the case of the isospin zero (I=0) and
two (I=2) channels are no bound states. And we find that the bound energy
depends strongly on pion mass rather than the ratio of pion mass to rho meson
mass.Comment: 7 pages, 4 figures, The 30th International Symposium on Lattice Field
Theor
A new relativistic viscous hydrodynamics code and its application to the Kelvin-Helmholtz instability in high-energy heavy-ion collisions
We construct a new relativistic viscous hydrodynamics code optimized in the
Milne coordinates. We split the conservation equations into an ideal part and a
viscous part, using the Strang spitting method. In the code a Riemann solver
based on the two-shock approximation is utilized for the ideal part and the
Piecewise Exact Solution (PES) method is applied for the viscous part. We check
the validity of our numerical calculations by comparing analytical solutions,
the viscous Bjorken's flow and the Israel-Stewart theory in Gubser flow regime.
Using the code, we discuss possible development of the Kelvin-Helmholtz
instability in high-energy heavy-ion collisions.Comment: 14 pages, 9 figure
Evaluating Results from the Relativistic Heavy Ion Collider with Perturbative QCD and Hydrodynamics
We review the basic concepts of perturbative quantum chromodynamics (QCD) and
relativistic hydrodynamics, and their applications to hadron production in high
energy nuclear collisions. We discuss results from the Relativistic Heavy Ion
Collider (RHIC) in light of these theoretical approaches. Perturbative QCD and
hydrodynamics together explain a large amount of experimental data gathered
during the first decade of RHIC running, although some questions remain open.
We focus primarily on practical aspects of the calculations, covering basic
topics like perturbation theory, initial state nuclear effects, jet quenching
models, ideal hydrodynamics, dissipative corrections, freeze-out and initial
conditions. We conclude by comparing key results from RHIC to calculations.Comment: 78 pages, 45 figures, 3 tables; to be published in Prog. Part. Nucl.
Phys; v2: a few references added, some typos fixe
First 4D lattice calculation of transport coefficient for pure gluon plasma
The transport coefficient plays a pivotal role in describing the
phenomenon of jet quenching in the quark-gluon plasma (QGP) produced in
ultra-relativistic nucleus-nucleus collisions. It is challenging to compute
this coefficient from first principles due to its non-perturbative nature. In
this article, we present an - formulation of based on the
standard techniques of perturbative quantum chromodynamics (pQCD) and lattice
gauge theory. We construct by considering a leading order (LO)
process where a hard parton produced from the hard scattering undergoes
transverse broadening due to scatterings with the thermal medium. We do an
analytic continuation to the Euclidean region and use the dispersion relation
to express in terms of series of local Field-Strength-Field-Strength
(FF) operators. Each term in the series is suppressed by the hard scale
. Finally, we compute the local operators on the quenched SU(3) lattice
and present our estimates for .Comment: 5 pages, 6 subfigures, International Conference on Hard and
Electromagnetic Probes of High-Energy Nuclear Collisions, 30 September - 5
October 2018, Aix-Les-Bains, Savoie, Franc
Masses of vector bosons in two-color dense QCD based on the hidden local symmetry
We construct a low energy effective Lagrangian for the two-color QCD
including the "vector" bosons (mesons with J^P=1^- and diquark baryons with
J^P=1^+) in addition to the pseudo Nambu-Goldstone bosons with a degenerate
mass M_\pi (mesons with J^P=0^- and baryons with J^P=0^+) based on the chiral
symmetry breaking pattern of SU(2N_f) \to Sp(2N_f) in the framework of the
hidden local symmetry. We investigate the dependence of the "vector" boson
masses on the baryon number density \mu_B. We show that the \mu_B-dependence
signals the phase transition of U(1)_B breaking. We find that it gives
information about mixing among "vector" bosons: e.g. the mass difference
between \rho and \omega mesons is proportional to the mixing strength between
the diquark baryon with J^P=1^+ and the anti-baryon. We discuss the comparison
with lattice data for two-color QCD at finite density.Comment: 24 pages, 5 figure
(3+1)-dimensional relativistic hydrodynamical expansion of hot and dense matter in ultra-relativistic nuclear collision
A full (3+1)-dimensional calculation using the Lagrangian hydrodynamics is
proposed for relativistic nuclear collisions. The calculation enables us to
evaluate anisotropic flow of hadronic matter which appears in non-central
and/or asymmetrical relativistic nuclear collisions. Applying hydrodynamical
calculations to the deformed uranium collisions at AGS energy region, we
discuss the nature of space-time structure and particle distributions in
detail.Comment: 24 pages, 25 eps figures, LaTeX 2 epsilo
A new relativistic hydrodynamics code for high-energy heavy-ion collisions
We construct a new Godunov type relativistic hydrodynamics code in Milne
coordinates, using a Riemann solver based on the two-shock approximation which
is stable under the existence of large shock waves. We check the correctness of
the numerical algorithm by comparing numerical calculations and analytical
solutions in various problems, such as shock tubes, expansion of matter into
the vacuum, the Landau-Khalatnikov solution, and propagation of fluctuations
around Bjorken flow and Gubser flow. We investigate the energy and momentum
conservation property of our code in a test problem of longitudinal
hydrodynamic expansion with an initial condition for high-energy heavy-ion
collisions. We also discuss numerical viscosity in the test problems of
expansion of matter into the vacuum and conservation properties. Furthermore,
we discuss how the numerical stability is affected by the source terms of
relativistic numerical hydrodynamics in Milne coordinates.Comment: 20 pages, 16 figure
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