102 research outputs found
Superconducting phase transition in the Nambu - Jona-Lasinio model
The Nambu - Bogoliubov - de Gennes method is applied to the problem of
superconducting QCD. The effective quark-quark interaction is described within
the framework of the Nambu - Jona-Lasinio model. The details of the phase
diagram are given as a function of the strength of the quark-quark coupling
constant . It is find that there is no superconducting phase
transition when one uses the relation between the coupling constants
and of the Nambu - Jona-Lasinio model which follows from the
Fierz transformation. However, for other values of one can find a
rich phase structure containing both the chiral and the superconducting phase
transitions.Comment: 7 pages, 3 figure
Evidence of strong higher twist effects in diffractive DIS at HERA at moderate Q2
We study a twist decomposition of diffractive structure functions in the
diffractive deep inelastic scattering (DDIS) at HERA. At low Q2 and at large
energy the data exhibit a strong excess, up to about 100%, above the twist 2
NLO DGLAP description. The excess in consistent with higher twist effects. It
is found, that complementing the DGLAP fit by twist 4 and 6 components of the
GBW saturation model leads to a good description of data at low Q2. We conclude
that the DDIS at HERA provides the first, strong evidence of higher twist
effects in DIS.Comment: 4 pages, 2 PDF figure
Coexistence of pion condensation and color superconductivity in two flavor quark matter
We show that the superconducting 2SC phase at high density and normal chiraly
broken quark phase at low density is separated by the mixed non-uniform phase
along the baryon density line.Comment: Change of the title. Journal-ref adda
Evidence for breakdown of the DGLAP description in diffractive DIS at HERA
HERA data on diffractive DIS show deviations from twist 2 DGLAP predictions
below GeV at low pomeron , which may reach up to 100%.
These deviations are consistent with higher twists effects extracted from the
saturation model. It is a first direct evidence for the higher twists in DIS.
This finding affects determination of the diffractive parton densities that are
used for the predictions at the LHC.Comment: 5 pages, 2 figures, Based on the talk presented at the conference
Deep-Inelastic Scattering and Related Subjects (DIS2012), Bonn, 201
Isgur - Wise Functions for Confined Light Quarks in a Colour Electric Potential
We explore the influence on the Isgur-Wise function of the colour electric
potential between heavy and light quarks in mesons. It is shown that in bag
models, its inclusion tends to restore light quark flavour symmetry relative to
the MIT bag predictions, and that relative to this model it flattens the
Isgur-Wise function. Results compare very well with observations.Comment: 9 pages, 1 figure (available upon request), Latex, TPJU - 4/9
Exclusive photo- and electroproduction at HERA as a possible probe of the odderon singularity in QCD
Theory and phenomenology of the eta_c photo- and electroproduction is
developed from the point of view of probing the odderon singularity in QCD
which corresponds to the three gluon exchange mechanism. This mechanism leads
to the cross-sections which are independent of W^2 for the exchange of three
non-interacting gluons or exhibit increase with increasing W^2 (or 1/x) for the
odderon intercept above unity. The \eta_c electroproduction in the three gluon
exchange mechanism is shown to be entirely controlled by the transversely
polarised virtual photons. The magnitude of the eta_c photoproduction
cross-section is estimated to be around 11-45pb. The t-dependence of the
differential cross-section is also discussed.Comment: 9 pages, LaTeX, uses epsfig.sty; Numerical error corrected. A factor
of 1/3 missing in amplitude in Eq.(8) added. Obtained gamma p -> eta_c p
cross-section smaller by a factor of 9 than in the original version of the
paper. Figures 4 and 5 changed accordingl
Meson bound states in multiflavour massive Schwinger model
The problem of meson bound states with massive fermions in two
dimensional quantum electrodynamics is discussed. We speculate about the
spectrum of the lightest particles by means of the effective semiclassical
description. In particular, the systems of fundamental fermions with
and flavour symmetries broken by massive terms are investigated.Comment: 16 page
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