6,532 research outputs found
QCD Thermodynamics from the Lattice
We review the current methods and results of lattice simulations of quantum
chromodynamics at nonzero temperatures and densities. The review is intended to
introduce the subject to interested nonspecialists and beginners. It includes a
brief overview of lattice gauge theory, a discussion of the determination of
the crossover temperature, the QCD phase diagram at zero and nonzero densities,
the equation of state, some in-medium properties of hadrons including
charmonium, and some plasma transport coefficients.Comment: 74 pp. 31 figs. To appear in the European Physical Journal A and
Advances in Physics of Particles and Nuclei. Added references, corrected
typos, and updated the discussion of the thermal heavy quark/antiquark
potential. Added and updated references. Final versio
Framework for non-perturbative analysis of a Z(3)-symmetric effective theory of finite temperature QCD
We study a three dimensional Z(3)-symmetric effective theory of high
temperature QCD. The exact lattice-continuum relations, needed in order to
perform lattice simulations with physical parameters, are computed to order
O(a^0) in lattice perturbation theory. Lattice simulations are performed to
determine the phase structure of a subset of the parameter space.Comment: 28 pages, 11 figures; v3: references rearranged, typos corrected,
figs changed, published versio
The triviality bound on the Higgs mass; its value and what it means
Older lattice work exploring the Higgs mass triviality bound is briefly
reviewed. It indicates that a strongly interacting scalar sector in the minimal
standard model cannot exist; on the other hand low energy QCD phenomenology
might be interpreted as an indication that it could. We attack this puzzle
using the expansion and discover a simple criterion for selecting a
lattice action that is more likely to produce a heavy Higgs particle. Depending
on the precise form of the limitation put on the cutoff effects, our large
calculations, when combined with old numerical data, suggest that the Higgs
mass bound might be around 750 , which is higher than the
previously obtained. Preliminary numerical work indicates that an increase of
at least 19\% takes place at on the lattice when the old simple
action is replaced with a new action (still containing only nearest neighbor
interactions) if one uses the lattice spacing as the physical cutoff for both
actions. It appears that, while a QCD like theory could produce , a meaningful ``minimal elementary Higgs'' theory cannot have M_H/ F~
\gtapprox 3. Still, even at 750 , the Higgs particle is so wide (GeV), that one cannot argue any more that the scalar sector is weakly
coupled.Comment: 8 pages. Latex file with 4 ps figures included. Preprint RU-92-22,
SCRI-92-11
Lattice quark propagator with staggered quarks in Landau and Laplacian gauges
We report on the lattice quark propagator using standard and improved
Staggered quark actions, with the standard, Wilson gauge action. The standard
Kogut-Susskind action has errors of \oa{2} while the ``Asqtad'' action has
\oa{4}, \oag{2}{2} errors. The quark propagator is interesting for studying the
phenomenon of dynamical chiral symmetry breaking and as a test-bed for
improvement. Gauge dependent quantities from lattice simulations may be
affected by Gribov copies. We explore this by studying the quark propagator in
both Landau and Laplacian gauges. Landau and Laplacian gauges are found to
produce very similar results for the quark propagator.Comment: 11 pages, 15 figure
Single spin asymmetries in inclusive hadron production from SIDIS to hadronic collisions: universality and phenomenology
In a perturbative QCD approach, with inclusion of spin and transverse
momentum effects, experimental data on azimuthal asymmetries observed in
polarized semi-inclusive deeply inelastic scattering and e+ e- annihilations
can be used to determine the Sivers, transversity and Collins soft functions.
By using these functions, within the same scheme, we predict p(transv.
polarized) p -> h + X single spin asymmetries in remarkable agreement with RHIC
experimental data.Comment: 5 pages, 6 ps figure
Eigenvalue distribution of the Dirac operator at finite temperature with (2+1)-flavor dynamical quarks using the HISQ action
We report on the behavior of the eigenvalue distribution of the Dirac
operator in (2+1)-flavor QCD at finite temperature, using the HISQ action. We
calculate the eigenvalue density at several values of the temperature close to
the pseudocritical temperature. For this study we use gauge field
configurations generated on lattices of size with two light
quark masses corresponding to pion masses of about 160 and 115 MeV. We find
that the eigenvalue density below receives large contributions from
near-zero modes which become smaller as the temperature increases or the light
quark mass decreases. Moreover we find no clear evidence for a gap in the
eigenvalue density up to 1.1. We also analyze the eigenvalue density near
where it appears to show a power-law behavior consistent with what is
expected in the critical region near the second order chiral symmetry restoring
phase transition in the massless limit.Comment: 7 pages, 7 figures, talk presented at the XXIX International
Symposium on Lattice Field Theory, July 10-16 2011, Squaw Valley, Lake Tahoe,
California, US
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