1,583 research outputs found
Spontaneous violation of chiral symmetry in QCD vacuum is the origin of baryon masses and determines baryon magnetic moments and their other static properties
A short review is presented of the spontaneous violation of chiral symmetry
in QCD vacuum. It is demonstrated, that this phenomenon is the origin of baryon
masses in QCD. The value of nucleon mass is calculated as well as the masses of
hyperons and some baryonic resonances and expressed mainly through the values
of quark condensates -- -- the vacuum
expectation values (v.e.v.) of quark field. The concept of vacuum expectation
values induced by external fields is introduced. It is demonstrated that such
v.e.v. induced by static electromagnetic field results in quark condensate
magnetic susceptibility, which plays the main role in determination of baryon
magnetic moments. The magnetic moments of proton, neutron and hyperons are
calculated. The results of calculation of baryon octet -decay constants
are also presented.Comment: 13 pades, 5 figures. Dedicated to 85-birthday of acad. S.T.Belyaev.
To be published in Phys.At.Nucl. Few references are correcte
Energy transport in strongly disordered superconductors and magnets
We develop an analytical theory for quantum phase transitions driven by
disorder in magnets and superconductors. We study these transitions with a
cavity approximation which becomes exact on a Bethe lattice with large
branching number. We find two different disordered phases, characterized by
very different relaxation rates, which both exhibit strong inhomogeneities
typical of glassy physics.Comment: 4 pages, 1 figur
Chirality violating condensates in QCD and their connection with zero mode solutions of quark Dirac equations
It is demonstrated, that chirality violating condensates in massless QCD
arise entirely from zero mode solutions of Dirac equations in arbitrary gluon
fields. The model is suggested, where the zero mode solutions are the ones for
quarks, moving in the instanton field. Basing on this model were calculated the
quark condensate magnetic susceptibilities of dimensions and 5
( and ). The good considence of the values and
, obtained in this approach with ones, found from the hadronic spectrum ia
a serious argument in favour, that instantons are the only source of chirality
violating condensates in QCD. The temperature dependence of the quark
condensate is discussed. It is shown that the phase transition, corresponding
to the -dependence of the quark condensate as an order
parameter, is of the type of crossover.Comment: The talk presented of Gribov-80 Workshop, May 28-30, 2010, Trieste, 8
pages, minor change
Structure functions for light nuclei
We discuss the nuclear EMC effect with particular emphasis on recent data for
light nuclei including 2H, 3He, 4He, 9Be, 12C and 14N. In order to verify the
consistency of available data, we calculate the \chi^2 deviation between
different data sets. We find a good agreement between the results from the NMC,
SLAC E139, and HERMES experiments. However, our analysis indicates an overall
normalization offset of about 2% in the data from the recent JLab E03-103
experiment with respect to previous data for nuclei heavier than 3He. We also
discuss the extraction of the neutron/proton structure function ratio F2n/F2p
from the nuclear ratios 3He/2H and 2H/1H. Our analysis shows that the E03-103
data on 3He/2H require a renormalization of about 3% in order to be consistent
with the F2n/F2p ratio obtained from the NMC experiment. After such a
renormalization, the 3He data from the E03-103 data and HERMES experiments are
in a good agreement. Finally, we present a detailed comparison between data and
model calculations, which include a description of the nuclear binding, Fermi
motion and off-shell corrections to the structure functions of bound proton and
neutron, as well as the nuclear pion and shadowing corrections. Overall, a good
agreement with the available data for all nuclei is obtained.Comment: 18 pages, 7 figures, 5 tables, final version published in Phys. Rev.
Effect of charmed meson loops on charmonium transitions
The effects of intermediate charmed mesons on charmonium transitions with the
emission of one pion or eta are studied systematically. Based on a
non-relativistic effective field theory we show that charmed meson loops are
enhanced compared to the corresponding tree-level contributions for transitions
between two S-wave charmonia as well as for transitions between two P-wave
charmonia. On the contrary, for the transitions between one S-wave and one
P-wave charmonium state, the loops need to be analyzed case by case and often
appear to be suppressed. The relation to and possible implications for an
effective Lagrangian approach are also discussed. This study at the same time
provides a cross check for the numerical evaluations.Comment: 50 pages, 13 figures. More discussions on the power counting, scaling
of the coupling constants discussed. Conclusions unchanged. Version accepted
for publication in PR
Improving Small Object Proposals for Company Logo Detection
Many modern approaches for object detection are two-staged pipelines. The
first stage identifies regions of interest which are then classified in the
second stage. Faster R-CNN is such an approach for object detection which
combines both stages into a single pipeline. In this paper we apply Faster
R-CNN to the task of company logo detection. Motivated by its weak performance
on small object instances, we examine in detail both the proposal and the
classification stage with respect to a wide range of object sizes. We
investigate the influence of feature map resolution on the performance of those
stages.
Based on theoretical considerations, we introduce an improved scheme for
generating anchor proposals and propose a modification to Faster R-CNN which
leverages higher-resolution feature maps for small objects. We evaluate our
approach on the FlickrLogos dataset improving the RPN performance from 0.52 to
0.71 (MABO) and the detection performance from 0.52 to 0.67 (mAP).Comment: 8 Pages, ICMR 201
The structure functions of longitudinal virtual photon at low virtualities
The structure functions of longitudinal virtual photon at low virtualities
are calculated in the framework of chiral pertubation theory(ChPT) in the zero
and first order of ChPT. It is assumed that the virtuality of target
longitudinal photon is much less than the virtuality of the hard projectile
photon and both are less than the characteristic ChPT scale.Comment: 16 pages, 8 figure
Implications of the Crystal Barrel data for meson-baryon symmetries
Making use of numerous resonances discovered by the Crystal Barrel
Collaboration we discuss some possible relations between the baryon and meson
spectra of resonances composed of the light non-strange quarks. Our goal is to
indicate new features that should be reproduced by the realistic dynamical
models describing the hadron spectrum in the sector of light quarks.Comment: Completely modified version; to appear in Mod. Phys. Lett.
The B_{s0} meson and the B_{s0}B K coupling from QCD sum rules
We evaluate the mass of the scalar meson and the coupling constant
in the vertex in the framework of QCD sum rules. We consider the
as a tetraquark state to evaluate its mass. We get m_{B_s0}=(6.04\pm
0.08) \GeV, which is bigger than predictions supposing it as a
state or a bound state with . To evaluate the coupling we use the three point correlation functions of the vertex,
considering as a normal state. The obtained coupling
constant is: g_{B_{s0} B K} =(16.3 \pm 3.2) \GeV. This number is in agreement
with light-cone QCD sum rules calculation. We have also compared the decay
width of the \BS\to BK process considering the \BS to be a state
and a molecular state. The width obtained for the molecular state is
twice as big as the width obtained for the state. Therefore, we
conclude that with the knowledge of the mass and the decay width of the \BS
meson, one can discriminate between the different theoretical proposals for its
structure.Comment: revised version to appear in Phys. Rev.
Nucleon spin content and axial coupling constants in QCD sum rules approach
The review of current experimental situation in the measurements of the first
moment of spin dependent nucleon structure functions
is presented. The results of the calculations of twist-4
corrections to are discussed and their accuracy is estimated.
The part of the proton spin carried by quarks is calculated
in the framework of the QCD sum rules in the external fields. The operators up
to dimension 9 are accounted. An important contribution comes from the operator
of dimension 3, which in the limit of massless quarks is equal to the
derivative of QCD topological susceptibility . The comparison with
the experimental data on gives . The limits on and are found from selfconsistency of
the sum rule, \Sigma \ga 0.05, \chi' (0) \ga 1.6 \times 10^{-3} GeV^2. The
values of and are also determined
from the corresponding sum rules.Comment: Lecture at St.Petersburg Winter School on Theoretical Physics, Febr.
23-28, 1998 to be published in Proceedings, 14 pages, LaTeX 2e, 4 eps figures
included using epsf.st
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