1,182 research outputs found
Sequential charmonium dissociation
Finite temperature lattice QCD indicates that the charmonium ground state
J/psi can survive in a quark-gluon plasma up to 1.5 T_c or more, while the
excited states chi_c and psi-prime are dissociated just above T_c. We assume
that the chi_c suffers the same form of suppression as that observed for the
psi-prime in SPS experiments, and that the directly produced J/psi is
unaffected at presently available energy densities. This provides a
parameter-free description of J/psi and psi-prime suppression which agrees
quite well with that observed in SPS and RHIC data.Comment: 10 pages, 8 figure
Phase Structure of Color Superconductivity
We investigate color superconductivity and chiral symmetry restoration at
finite temperature and baryon density in the frame of standard two flavor
Nambu--Jona-Lasinio model. We derive the diquark mass in RPA, discuss its
constraint on the coupling constant in the diquark channel, and find a strong
competition between the two phase transitions when the coupling constant is
large enough.Comment: Talk presented at Conference on Non-Perturbative Quantum Field
Theory: Lattice and Beyond, Guangzhou, China, Dec.16--18, 200
Infrared features of unquenched finite temperature lattice Landau gauge QCD
The color diagonal and color antisymmetric ghost propagators slightly above
of MILC lattices are measured and compared with
zero temperature unquenched MILC and MILC
lattices and zero temperature quenched and
6.45 lattices. The expectation value of the color antisymmetric ghost
propagator is zero but its Binder cumulant, which is consistent
with that of dimensional Gaussian distribution below , decreases
above . Although the color diagonal ghost propagator is temperature
independent, the norm of the color antisymmetric ghost propagator is
temperature dependent. The expectation value of the ghost condensate observed
at zero temperature unquenched configuration is consistent with 0 in .
We also measure transverse, magnetic and electric gluon propagator and
extract gluon screening masses. The running coupling measured from the product
of the gluon dressing function and the ghost dressing function are almost
temperature independent but the effect of condensate observed at zero
temperature is consistent with 0 in .
The transverse gluon dressing function at low temperature has a peak in the
infrared but it becomes flatter at high temperature. Its absolute value in the
high momentum is larger for high temperature and similar to the magnetic gluon
dressing function. The electric gluon propagator at high momentum is
temperature independent. These data imply that the magnetic gluon propagator
and the color antisymmetric ghost propagator are affected by the presence of
dynamical quarks and there are strong non-perturbative effects through the
temperature dependent color anti-symmetric ghost propagator.Comment: 11 pages 16 figures, version accepted for publication in Phys. Rev.
The QCD phase diagram: A comparison of lattice and hadron resonance gas model calculations
We compare the lattice results on QCD phase diagram for two and three flavors
with the hadron resonance gas model (HRGM) calculations. Lines of constant
energy density have been determined at different baryo-chemical
potentials . For the strangeness chemical potentials , we use two
models. In one model, we explicitly set for all temperatures and
baryo-chemical potentials. This assignment is used in lattice calculations. In
the other model, is calculated in dependence on and
according to the condition of vanishing strangeness. We also derive an
analytical expression for the dependence of on by applying
Taylor expansion of . In both cases, we compare HRGM results on
diagram with the lattice calculations. The agreement is excellent,
especially when the trigonometric function of is truncated up to the
same order as done in lattice simulations. For studying the efficiency of the
truncated Taylor expansion, we calculate the radius of convergence. For zero-
and second-order radii, the agreement with lattice is convincing. Furthermore,
we make predictions for QCD phase diagram for non-truncated expressions and
physical masses. These predictions are to be confirmed by heavy-ion experiments
and future lattice calculations with very small lattice spacing and physical
quark masses.Comment: 25 pages, 8 eps figure
QCD strings and the thermodynamics of the metastable phase of QCD at large
The thermodyanmics of a metastable hadronic phase of QCD at large are
related to properties of an effective QCD string. In particular, it is shown
that in the large limit and near the maximum hadronic temperature, ,
the energy density and pressure of the metastable phase scale as (for ) and (for ) where is the effective
number of transverse dimensions of the string theory. It is shown, however,
that for the thermodynamic quantities of interest the limits and
do not commute. The prospect of extracting via
lattice simulations of the metastable hadronic phase at moderately large
is discussed.Comment: After this paper was published, the author became aware of an
important early paper by Charles Thorn on the subject of the QCD phase
transition at large N_c and its relation to the Hagedorn spectrum. Given the
pioneering nature of Thorn's paper, and the fact that it is not as widely
known as it should be, it is important to cite it in the present work. This
updated version cites Thorn's wor
Near-field coupling of gold plasmonic antennas for sub-100 nm magneto-thermal microscopy
The development of spintronic technology with increasingly dense, high-speed,
and complex devices will be accelerated by accessible microscopy techniques
capable of probing magnetic phenomena on picosecond time scales and at deeply
sub-micron length scales. A recently developed time-resolved magneto-thermal
microscope provides a path towards this goal if it is augmented with a
picosecond, nanoscale heat source. We theoretically study adiabatic
nanofocusing and near-field heat induction using conical gold plasmonic
antennas to generate sub-100 nm thermal gradients for time-resolved
magneto-thermal imaging. Finite element calculations of antenna-sample
interactions reveal focused electromagnetic loss profiles that are either
peaked directly under the antenna or are annular, depending on the sample's
conductivity, the antenna's apex radius, and the tip-sample separation. We find
that the thermal gradient is confined to 40 nm to 60 nm full width at half
maximum for realistic ranges of sample conductivity and apex radius. To
mitigate this variation, which is undesirable for microscopy, we investigate
the use of a platinum capping layer on top of the sample as a thermal
transduction layer to produce heat uniformly across different sample materials.
After determining the optimal capping layer thickness, we simulate the
evolution of the thermal gradient in the underlying sample layer, and find that
the temporal width is below 10 ps. These results lay a theoretical foundation
for nanoscale, time-resolved magneto-thermal imaging.Comment: 24 pages including Supporting Information, 6 figures in the main
text, 4 supporting figure
A Family of Equations of State Based on Lattice QCD: Impact on Flow in Ultrarelativistic Heavy-Ion Collisions
We construct a family of equations of state within a quasiparticle model by
relating pressure, energy density, baryon density and susceptibilities adjusted
to first-principles lattice QCD calculations. The relation between pressure and
energy density from lattice QCD is surprisingly insensitive to details of the
simulations. Effects from different lattice actions, quark masses and lattice
spacings used in the simulations show up mostly in the quark-hadron phase
transition region which we bridge over by a set of interpolations to a hadron
resonance gas equation of state. Within our optimized quasiparticle model we
then examine the equation of state along isentropic expansion trajectories at
small net baryon densities, as relevant for experiments and hydrodynamic
simulations at RHIC and LHC energies. We illustrate its impact on azimuthal
flow anisotropies and transverse momentum spectra of various hadron species
QCD matter within a quasi-particle model and the critical end point
We compare our quasi-particle model with recent lattice QCD results for the
equation of state at finite temperature and baryo-chemical potential. The
inclusion of the QCD critical end point into models is discussed. We propose a
family of equations of state to be employed in hydrodynamical calculations of
particle spectra at RHIC energies and compare with the differential azimuthal
anisotropy of strange and charm hadrons.Comment: talk at Quark Matter 2005, August 4 - 9, 2005, Budapest, Hungar
Glueball enhancement by color de-confinement
High energy heavy ion collisions lead to the formation of a strong coupling
de-confined phase in which the lightest glueballs are numerous and stable. We
analyze how their properties manifest themselves in experimental spectra and
show that they provide a good signature for color de-confinement.Comment: 9 pages, 4 figure
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