128 research outputs found
Sea-quark flavor asymmetry in the nucleon from a relativistic analysis of the Drell-Yan scattering off nuclei
It is shown that accounting for the relativistic structure of the deuteron
allows to explain the ratio of the Drell-Yan pair production cross-section at
the low Bjorken off the deuteron and the proton. Thus, the sea quark
distributions in the nucleon should be studied with accounting for the effects
of the relativistic structure of the deuteron. The suggested approach reduces
theoretical uncertainty in extracting the ratio from the data
and it is important for the clarification of the nature of the sea quark
asymmetry in the nucleon.Comment: 4 pages, 1 figures, Chiral Symmetry in Hadron and Nuclear Physics
November 13-16, 2007, Osak
Observation of deconfinement in a cold dense quark medium
In this paper we study the confinement/deconfinement transition in lattice
QCD at finite quark density and zero temperature. The simulations are
performed on an lattice with rooted staggered fermions at a lattice
spacing . This small lattice spacing allowed us to
reach very large baryon density (up to quark chemical potential ) avoiding strong lattice artifacts. In the region we observe for the first time the confinement/deconfinement
transition which manifests itself in rising of the Polyakov loop and vanishing
of the string tension . After the deconfinement is achieved at , we observe a monotonous decrease of the spatial string
tension which ends up with vanishing at . From this observation we draw the conclusion that the
confinement/deconfinement transition at finite density and zero temperature is
quite different from that at finite temperature and zero density. Our results
indicate that in very dense matter the quark-gluon plasma is in essence a
weakly interacting gas of quarks and gluons without a magnetic screening mass
in the system, sharply different from a quark-gluon plasma at large
temperature.Comment: 6 pages, 4 figure
Lattice QCD thermodynamics at finite chemical potential and its comparison with Experiments
We compare higher moments of baryon numbers measured at the RHIC heavy ion
collision experiments with those by the lattice QCD calculations. We employ the
canonical approach, in which we can access the real chemical potential regions
avoiding the sign problem. In the lattice QCD simulations, we study several
fits of the number density in the pure imaginary chemical potential, and
analyze how these fits affects behaviors at the real chemical potential. In the
energy regions between =19.6 and 200 GeV, the susceptibility
calculated at is consistent with experimental data at , while the kurtosis shows similar behavior with that of the
experimental data in the small regions . The
experimental data at 11.5 shows quite different behavior. The
lattice result in the deconfinement region,, is far from
experimental data
Temperature dependence of the axial magnetic effect in two-color quenched QCD
The Axial Magnetic Effect is the generation of an equilibrium dissipationless
energy flow of chiral fermions in the direction of the axial (chiral) magnetic
field. At finite temperature the dissipationless energy transfer may be
realized in the absence of any chemical potentials. We numerically study the
temperature behavior of the Axial Magnetic Effect in quenched SU(2) lattice
gauge theory. We show that in the confinement (hadron) phase the effect is
absent. In the deconfinement transition region the conductivity quickly
increases, reaching the asymptotic behavior in a deep deconfinement
(plasma) phase. Apart from an overall proportionality factor, our results
qualitatively agree with theoretical predictions for the behavior of the energy
flow as a function of temperature and strength of the axial magnetic field.Comment: 5 pages, 1 figur
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