8,992 research outputs found
QCD and the eta prime Mass: Instantons or Confinement?
We argue that lattice calculations of the mass in QCD with
colors performed at non-zero baryon chemical potential can be used to study the
mechanism responsible for the mass of the . QCD with two colors is an
ideal laboratory because it exhibits confinement, chiral symmetry breaking and
a would-be Goldstone boson at all densities. Since the instanton
density and the confinement scale vary with density in a very different way,
instantons are clearly distinguishable from other possible mechanisms. There is
an instanton prediction for the mass at large density that can be
compared to lattice results. The density dependence of the instanton
contribution is a simple consequence of the integer topological charge carried
by the instanton. We also argue that color QCD at finite isospin
density can be used in order to study the origin of OZI-violation in the scalar
sector.Comment: 6 pages, 2 figure
Magnetic anisotropies and magnetization reversal of the CoCrFeAl Heusler compound
Magnetic anisotropies and magnetization reversal properties of the epitaxial
Heusler compound CoCrFeAl (CCFA) deposited on Fe and Cr
buffer layers are studied. Both samples exhibit a growth-induced fourfold
anisotropy, and magnetization reversal occurs through the formation of stripy
domains or 90 degree domains. During rotational magnetometric scans the sample
deposited on Cr exhibits about 2 degree sharp peaks in the angular dependence
of the coercive field, which are oriented along the hard axis directions. These
peaks are a consequence of the specific domain structure appearing in this
particular measurement geometry. A corresponding feature in the sample
deposited on Fe is not observed.Comment: 11 pages, 7 figure
Diffractive Hard Dijets and Nuclear Parton Distributions
Diffraction plays an exceptional role in DIS off heavy nuclei. First,
diffraction into hard dijets is an unique probe of the unintegrated glue in the
target. Second, because diffraction makes 50 per cent of total DIS off a heavy
target, understanding diffraction in a saturation regime is crucial for a
definition of saturated nuclear parton densities. After brief comments on the
Nikolaev-Zakharov (NZ) pomeron-splitting mechanism for diffractive hard dijet
production, I review an extension of the Nikolaev-Schafer-Schwiete (NSS)
analysis of diffractive dijet production off nuclei to the definition of
nuclear partons in the saturation regime. I emphasize the importance of
intranuclear final state interactions for the parton momentum distributions.Comment: 9 pages, 2 figures, to be published in Proceedings of the Workshop on
Exclusive Processes at High Momentum Transfer, Jefferson Lab, May 15-18,
2002. Typos corrected, discussion of the results extende
High Density QCD, Saturation and Diffractive DIS
We review a consistent description of the fusion and saturation of partons in
the Lorentz-contracted ultrarelativistic nuclei in terms of a nuclear
attenuation of color dipole states of the photon and collective
Weizs\"acker-Williams (WW) gluon structure function of a nucleus. Diffractive
DIS provides a basis for the definition of the WW nuclear glue. The point that
all observables for DIS off nuclei are uniquely calculable in terms of the
nuclear WW glue amounts to a new form of factorization in the saturation
regime.Comment: 13 pages, 4 figures, Invited talk at NATO Advanced Research Workshop
On Diffraction 2002, 31 Aug - 6 Sep 2002, Alushta, Ukrain
Superdense Matter
We review recent work on the phase structure of QCD at very high baryon
density. We introduce the phenomenon of color superconductivity and discuss the
use of weak coupling methods. We study the phase structure as a function of the
number of flavors and their masses. We also introduce effective theories that
describe low energy excitations at high baryon density. Finally, we study the
possibility of kaon condensation at very large baryon density.Comment: 13 pages, talk at ICPAQGP, Jaipur, India, Nov. 26-30, 2001; to appear
in the proceeding
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