38 research outputs found
S-Wave Quarkonia in Potential Models
We discuss S-wave quarkonia correlators and spectral function using the
Wong-potential, and show that these do not agree with the lattice results.Comment: based on talk presented at Strangeness in Quark Matter, UCLA, March
26-31, 200
Induced Universal Properties and Deconfinement
We propose a general strategy to determine universal properties induced by a
nearby phase transition on a non-order parameter field. A general
renormalizable Lagrangian is used, which contains the order parameter and a
non-order parameter field, and respects all the symmetries present. We
investigate the case in which the order parameter field depends only on space
coordinates and the case in which this field is also time dependent. We find
that the spatial correlators of the non-order parameter field, in both cases,
are infrared dominated and can be used to determine properties of the phase
transition. We predict a universal behavior for the screening mass of a generic
singlet field, and show how to extract relevant information from such a
quantity. We also demonstrate that the pole mass of the non-order parameter
field is not infrared sensitive. Our results can be applied to any continuous
phase transition. As an example we consider the deconfining transition in pure
Yang-Mills theory, and show that our findings are supported by lattice data.
Our analysis suggests that monitoring the spatial correlators of different
hadron species, more specifically the derivatives of these, provides an
efficient and sufficient way to experimentally uncover the deconfining phase
transition and its features.Comment: Added computational details and improved the text. The results are
unchange
Critical Behavior of Non Order-Parameter Fields
We show that all of the relevant features of a phase transition can be
determined using a non order parameter field which is a physical state of the
theory. This fact allows us to understand the deconfining transition of the
pure Yang-Mills theory via the physical excitations rather than using the
Polyakov loop.Comment: RevTeX, 4-pages, 1 figur
Progress in finite temperature lattice QCD
I review recent progress in finite temperature lattice calculations,
including the determination of the transition temperature, equation of state,
screening of static quarks and meson spectral functions.Comment: 8 pages, LaTeX, uses iopart.cls, invited talk presented at
Strangeness in Quark Matter 2007 (SQM 2007), Levoca, Slovakia, June 24-29,
200
Chiral Phase Transition within Effective Models with Constituent Quarks
We investigate the chiral phase transition at nonzero temperature and
baryon-chemical potential within the framework of the linear sigma
model and the Nambu-Jona-Lasinio model. For small bare quark masses we find in
both models a smooth crossover transition for nonzero and and a
first order transition for T=0 and nonzero . We calculate explicitly the
first order phase transition line and spinodal lines in the plane.
As expected they all end in a critical point. We find that, in the linear sigma
model, the sigma mass goes to zero at the critical point. This is in contrast
to the NJL model, where the sigma mass, as defined in the random phase
approximation, does not vanish. We also compute the adiabatic lines in the
plane. Within the models studied here, the critical point does not
serve as a ``focusing'' point in the adiabatic expansion.Comment: 22 pages, 18 figure
Effective Lagrangians for Orientifold Theories
We construct effective Lagrangians of the Veneziano-Yankielowicz (VY) type
for two non-supersymmetric theories which are orientifold daughters of
supersymmetric gluodynamics (containing one Dirac fermion in the two-index
antisymmetric or symmetric representation of the gauge group). Since the parent
and daughter theories are planar equivalent, at N\to\infty the effective
Lagrangians in the orientifold theories basically coincide with the bosonic
part of the VY Lagrangian.
We depart from the supersymmetric limit in two ways. First, we consider
finite (albeit large) values of N. Then 1/N effects break supersymmetry. We
suggest seemingly the simplest modification of the VY Lagrangian which
incorporates these 1/N effects, leading to a non-vanishing vacuum energy
density. We analyze the spectrum of the finite-N non-supersymmetric daughters.
For N=3 the two-index antisymmetric representation (one flavor) is equivalent
to one-flavor QCD. We show that in this case the scalar quark-antiquark state
is heavier than the corresponding pseudoscalar state, `` eta' ''. Second, we
add a small fermion mass term. The fermion mass term breaks supersymmetry
explicitly. The vacuum degeneracy is lifted. The parity doublets split. We
evaluate the splitting. Finally, we include the theta-angle and study its
implications.Comment: LaTeX, 21 page
QCD-like theories at nonzero temperature and density
We investigate the properties of hot and/or dense matter in QCD-like theories
with quarks in a (pseudo)real representation of the gauge group using the
Nambu-Jona-Lasinio model. The gauge dynamics is modeled using a simple lattice
spin model with nearest-neighbor interactions. We first keep our discussion as
general as possible, and only later focus on theories with adjoint quarks of
two or three colors. Calculating the phase diagram in the plane of temperature
and quark chemical potential, it is qualitatively confirmed that the critical
temperature of the chiral phase transition is much higher than the
deconfinement transition temperature. At a chemical potential equal to half of
the diquark mass in the vacuum, a diquark Bose-Einstein condensation (BEC)
phase transition occurs. In the two-color case, a Ginzburg-Landau expansion is
used to study the tetracritical behavior around the intersection point of the
deconfinement and BEC transition lines, which are both of second order. We
obtain a compact expression for the expectation value of the Polyakov loop in
an arbitrary representation of the gauge group (for any number of colors),
which allows us to study Casimir scaling at both nonzero temperature and
chemical potential.Comment: JHEP class, 31 pages, 7 eps figures; v2: error in Eq. (3.11) fixed,
two references added; matches published versio
Thermal Dileptons at LHC
We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb
collisions at LHC. Hadronic emission in the low-mass region is calculated using
in-medium spectral functions of light vector mesons within hadronic many-body
theory. In the intermediate-mass region thermal radiation from the Quark-Gluon
Plasma, evaluated perturbatively with hard-thermal loop corrections, takes
over. An important source over the entire mass range are decays of correlated
open-charm hadrons, rendering the nuclear modification of charm and bottom
spectra a critical ingredient.Comment: 2 pages, 2 figures, contributed to Workshop on Heavy Ion Collisions
at the LHC: Last Call for Predictions, Geneva, Switzerland, 14 May - 8 Jun
2007 v2: acknowledgment include
Disoriented Chiral Condensate: Theory and Experiment
It is thought that a region of pseudo-vacuum, where the chiral order
parameter is misaligned from its vacuum orientation in isospin space, might
occasionally form in high energy hadronic or nuclear collisions. The possible
detection of such disoriented chiral condensate (DCC) would provide useful
information about the chiral structure of the QCD vacuum and/or the chiral
phase transition of strong interactions at high temperature. We review the
theoretical developments concerning the possible DCC formation in high-energy
collisions as well as the various experimental searches that have been
performed so far. We discuss future prospects for upcoming DCC searches, e.g.
in high-energy heavy-ion collision experiments at RHIC and LHC.Comment: 120 pages, 52 figures. Uses elsart.cls. To appear in Physics Reports.
Minor corrections, references adde