We have developed an event-by-event relativistic kinetic transport approach to study the build up of the anisotropic flows
v
n
(
p
T
)
for a system at fixed
η
/
s
(
T
)
. The partonic approach ...describe the evolution of massless partons which imply
ϵ
=
3
p
as Equation of State (EoS). We extend previous studies to finite partonic masses tuned to simulate a system that expand with an EoS close to the recent lQCD results. We study the role of EoS and the effect of
η
/
s
(
T
)
ratio on the build up of
v
n
(
p
T
)
up to
n
=
5
for two beam energies: RHIC energies at
s
=
200
GeV and LHC energies at
s
=
2.76
TeV. We find that for the two beam energies considered the suppression of the
v
n
(
p
T
)
due to the viscosity of the medium have different contributions coming from the cross over or QGP phase. We shows that in ultra-central collisions (0–0.2%) the
v
n
(
p
T
)
have a stronger sensitivity to the T dependence of
η
/
s
that increases with the order of the harmonic n. Finally, we discuss the results for the integrated flow harmonics
⟨
v
n
⟩
in ultra-central collisions pointing-out how the relative strength of
⟨
v
n
⟩
depend on the colliding energies as well as on the freeze-out dynamics.
In a coalescence plus fragmentation approach we calculate the heavy baryon/meson ratio and the
p
T
spectra of charmed hadrons
D
0
,
D
s
and
Λ
c
+
in a wide range of transverse momentum from low
p
T
...up to about 10 GeV and discuss their ratios from RHIC to LHC energies without any change of the coalescence parameters. We have included the contribution from decays of heavy hadron resonances and also the one due to fragmentation of heavy quarks which do not undergo the coalescence process. The coalescence process is tuned to have all charm quarks hadronizing in the
p
T
→
0
limit and at finite
p
T
charm quarks not undergoing coalescence are hadronized by independent fragmentation. The
p
T
dependence of the baryon/meson ratios are found to be sensitive to the masses of coalescing quarks, in particular the
Λ
c
/
D
0
can reach values of about
1
÷
1.5
at
p
T
≈
3
GeV, or larger, similarly to the light baryon/meson ratio like
p
/
π
and
Λ
/
K
, however a marked difference is a quite weak
p
T
dependence with respect to the light case, such that a larger value at intermediate
p
T
implies a relatively large value also for the integrated yields. A comparison with other coalescence model and with the prediction of thermal model is discussed.
Ultra-relativistic Heavy-Ion Collision (HIC) generates very strong initial magnetic field (B→) inducing a vorticity in the reaction plane. The high B→ influences the evolution dynamics that is ...opposed by the large Faraday current due to electric field generated by the time varying B→. We show that the resultant effects entail a significantly large directed flow (v1) of charm quarks (CQs) compared to light quarks due to a combination of several favorable conditions for CQs, mainly: (i) unlike light quarks formation time scale of CQs, τf≃0.1 fm/c is comparable to the time scale when B→ attains its maximum value and (ii) the kinetic relaxation time of CQs is similar to the QGP lifetime, this helps the CQ to retain the initial kick picked up from the electromagnetic field in the transverse direction. The effect is also odd under charge exchange allowing to distinguish it from the vorticity of the bulk matter due to the initial angular momentum conservation; conjointly thanks to its mass, Mc>>ΛQCD, there should be no mixing with the chiral magnetic dynamics. Hence CQs provide very crucial and independent information on the strength of the magnetic field produced in HIC.
A current goal of relativistic heavy-ion collisions experiments is the search for a Color Glass Condensate (CGC) as the limiting state of QCD matter at very high density. In viscous hydrodynamics ...simulations, a standard Glauber initial condition leads to estimate 4πη/s∼1, while employing the Kharzeev–Levin–Nardi (KLN) modeling of the glasma leads to at least a factor of 2 larger η/s. Within a kinetic theory approach based on a relativistic Boltzmann-like transport simulation, our main result is that the out-of-equilibrium initial distribution reduces the efficiency in building-up the elliptic flow. At RHIC energy we find the available data on v2 are in agreement with a 4πη/s∼1 also for KLN initial conditions. More generally, our study shows that the initial non-equilibrium in p-space can have a significant impact on the build-up of anisotropic flow.
We report on broadly based systematic investigations of the modeling components for open heavy-flavor diffusion and energy loss in strongly interacting matter in their application to heavy-flavor ...observables in high-energy heavy–ion collisions, conducted within an EMMI Rapid Reaction Task Force framework. Initial spectra including cold-nuclear-matter effects, a wide variety of space-time evolution models, heavy-flavor transport coefficients, and hadronization mechanisms are scrutinized in an effort to quantify pertinent uncertainties in the calculations of nuclear modification factors and elliptic flow of open heavy-flavor particles in nuclear collisions. We develop procedures for error assessments and criteria for common model components to improve quantitative estimates for the (low-momentum) heavy-flavor diffusion coefficient as a long-wavelength characteristic of QCD matter as a function of temperature, and for energy loss coefficients of high-momentum heavy-flavor particles.
We study the evolution of the quark-gluon composition of the plasma created in ultra-Relativistic Heavy-Ion Collisions (uRHICʼs) employing a partonic transport theory that includes both elastic and ...inelastic collisions plus a mean fields dynamics associated to the widely used quasi-particle model. The latter, able to describe lattice QCD thermodynamics, implies a “chemical” equilibrium ratio between quarks and gluons strongly increasing as T→Tc, the phase transition temperature. Accordingly we see in realistic simulations of uRHICʼs a rapid evolution from a gluon dominated initial state to a quark dominated plasma close to Tc. The quark-to-gluon ratio can be modified by about a factor of ∼20 in the bulk of the system and appears to be large also in the high pT region.
We discuss how this aspect, often overflown, can be important for a quantitative study of several key issues in the QGP physics: shear viscosity, jet quenching, quarkonia suppression. Furthermore a bulk plasma made by more than 80% of quarks plus antiquarks provides a theoretical basis for hadronization via quark coalescence.
In this article we report our results about quark production and chemical equilibration of quark–gluon plasma. Our initial condition corresponds to a classic Yang–Mills spectrum, in which only gluon ...degrees of freedom are considered; the initial condition is then evolved to a quark–gluon plasma by means of relativistic transport theory with inelastic processes which permit the conversion of gluons to qq¯ pairs. We then compare our results to the ones obtained with a standard Glauber model initialization. We find that regardless of the initial condition the final stage of the system contains an abundant percentage of qq¯ pairs; moreover spanning the possible coupling from weak to strong we find that unless the coupling is unrealistically small, both production rate and final percentage of fermions are quite large.
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