163 research outputs found
Structural Vertices of Extended SU(3)-Chiral Lagrangians in the Large-N_c Approach
The main goal of this paper is to elaborate the model-framework
parametrization of effective coupling constants of the extended chiral
lagrangian which is suitable for the description of the low-energy matrix
elements of vector, axial-vector, scalar and pseudoscalar currents as well as
of the matrix elements of the pseudoscalar gluon density. We establish the
connection between the structural coupling constants of the phenomenological
chiral lagrangian and the coefficients of effective lagrangians obtained in the
QCD-bosonization models by means of the derivative expansion. The large-N_c
relations for corresponding structural constants are elaborated. On this way we
find the new set of OZI rules. In particular, one of them predicts the
branching ratio of the decays or .Comment: 7 pages, LaTeX, Preprint SPbU-IP-94-1, Talk at the Workshop on Chiral
Perturbation Theory and Other Effective Theories (Karreb{\ae}ksminde,
Denmark, Sept.1993
Qualitative solution of QCD sum rules
We show how such important features of QCD as chiral symmetry breaking or the
formation of a mass-gap can be directly traced from QCD sum rules for two point
functions assuming, in the large number of colors limit, exact duality between
the operator product expansion and the spectrum described by linearly (or
nearly linear) rising Regge trajectories as predicted by string theory. We see
how the presence of chiral symmetry breaking is intimately related to
confinement in this scenario, as expected from general arguments, and how Regge
trajectories change when chiral symmetry is broken. As a result the whole meson
mass spectrum can be parametrized with a good accuracy by the constant
only, thus realizing the program proposed by Migdal some time ago.Comment: Version published in JHE
Classical Solutions in a Lorentz-violating Maxwell-Chern-Simons Electrodynamics
We take as starting point the planar model arising from the dimensional
reduction of the Maxwell Electrodynamics with the (Lorentz-violating)
Carroll-Field-Jackiw term. We then write and study the extended Maxwell
equations and the corresponding wave equations for the potentials. The solution
to these equations show some interesting deviations from the usual MCS
Electrodynamics, with background-dependent correction terms. In the case of a
time-like background, the correction terms dominate over the MCS sector in the
region far from the origin, and establish the behaviour of a massless
Electrodynamics (in the electric sector). In the space-like case, the solutions
indicate the clear manifestation of spatial anisotropy, which is consistent
with the existence of a privileged direction is space.Comment: latex, 8 page
Charmed particles production in pA-interactions at 70 GeV
The results of the SERP-E-184 experiment at the U-70 accelerator (IHEP,
Protvino) are presented. Interactions of the 70 GeV proton beam with carbon,
silicon and lead targets were studied to detect decays of charmed , , , mesons and baryon near their production
threshold. Measurements of lifetimes and masses have shown a good agreement
with PDG data. The inclusive cross sections of charm production and their
A-dependencies have been obtained. The yields of these particles are compared
with the theoretical predictions and the data of other experiments. The
measured cross section of the total open charm production b/nucleon at the collision c.m. energy
= 11.8 GeV is well above the QCD model predictions. The contributions
of different kinds of charmed particles to the total cross section of the open
charm production in proton-nucleus interactions vary with energy.Comment: Presented at 19th International Seminar on High Energy Physics
QUARKS-2016 (Pushkin, Russia, 29 May - 4 June, 2016.). 11 pages, 9 figure
Preface: “Quarks-2016”, 19th International Seminar on High Energy Physics
The highlights of the most recent CMS results with 13 TeV data will be presented in this overview. The Standard Model precision measurements, including the top quark production, will be shown first. This will be followed by the presentation of Higgs boson studies with the early 13 TeV data. Then the focus will shift to searches for physics beyond the Standard Model, including the searches for several Supersymmetric scenarios, using different analysis techniques. The talk will conclude with searches for the exotic resonances, with an emphasis on studies of the high-mass diphoton production
Spontaneous Breaking of Lorentz Invariance
We describe how a stable effective theory in which particles of the same
fermion number attract may spontaneously break Lorentz invariance by giving
non-zero fermion number density to the vacuum (and therefore dynamically
generating a chemical potential term). This mecanism yields a finite vacuum
expectation value could relate to work on signals of Lorentz violation
in electrodynamics.Comment: revtex4, 11 pages, 5 figures; v2:references added; v3:more references
added, typos fixed, some points in sect. IV clarified; v4:even more
references added, discussion in sect. V extended; v5:replaced to match
published version (minor corrections of form
Consistency analysis of a nonbirefringent Lorentz-violating planar model
In this work analyze the physical consistency of a nonbirefringent
Lorentz-violating planar model via the analysis of the pole structure of its
Feynman propagators. The nonbirefringent planar model, obtained from the
dimensional reduction of the CPT-even gauge sector of the standard model
extension, is composed of a gauge and a scalar fields, being affected by
Lorentz-violating (LIV) coefficients encoded in the symmetric tensor
. The propagator of the gauge field is explicitly evaluated
and expressed in terms of linear independent symmetric tensors, presenting only
one physical mode. The same holds for the scalar propagator. A consistency
analysis is performed based on the poles of the propagators. The isotropic
parity-even sector is stable, causal and unitary mode for .
On the other hand, the anisotropic sector is stable and unitary but in general
noncausal. Finally, it is shown that this planar model interacting with a
Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio
Spontaneous P-violation in QCD in extreme conditions
We investigate the possibility of parity being spontaneously violated in QCD
at finite baryon density and temperature. The analysis is done for an idealized
homogeneous and infinite nuclear matter where the influence of density can be
examined with the help of constant chemical potential. QCD is approximated by a
generalized sigma-model with two isomultiplets of scalars and pseudoscalars.
The interaction with the chemical potential is introduced via the coupling to
constituent quark fields as nucleons are not considered as point-like degrees
of freedom in our approach. This mechanism of parity violation is based on
interplay between lightest and heavier degrees of freedom and it cannot be
understood in simple models retaining the pion and nucleon sectors solely. We
argue that, in the appropriate environment (dense and hot nuclear matter of a
few normal densities and moderate temperatures), parity violation may be the
rule rather than the exception and its occurrence is well compatible with the
existence of stable bound state of normal nuclear matter. We prove that the so
called 'chiral collapse' never takes place for the parameter region supporting
spontaneous parity violation.Comment: 9 page
Supersymmetric Extension of the Lorentz and CPT-Violating Maxwell-Chern-Simons Model
Focusing on gauge degrees of freedom specified by a 1+3 dimensions model
hosting a Maxwell term plus a Lorentz and CPT non-invariant Chern-Simons-like
contribution, we obtain a minimal extension of such a system to a
supersymmetric environment. We comment on resulting peculiar self-couplings for
the gauge sector, as well as on background contribution for gaugino masses.
Furthermore, a non-polynomial generalization is presented.Comment: revtex4, 4 pages, no figure
Domain wall generation by fermion self-interaction and light particles
A possible explanation for the appearance of light fermions and Higgs bosons
on the four-dimensional domain wall is proposed. The mechanism of light
particle trapping is accounted for by a strong self-interaction of
five-dimensional pre-quarks. We obtain the low-energy effective action which
exhibits the invariance under the so called \tau-symmetry. Then we find a set
of vacuum solutions which break that symmetry and the five-dimensional
translational invariance. One type of those vacuum solutions gives rise to the
domain wall formation with consequent trapping of light massive fermions and
Higgs-like bosons as well as massless sterile scalars, the so-called branons.
The induced relations between low-energy couplings for Yukawa and scalar field
interactions allow to make certain predictions for light particle masses and
couplings themselves, which might provide a signature of the higher dimensional
origin of particle physics at future experiments. The manifest translational
symmetry breaking, eventually due to some gravitational and/or matter fields in
five dimensions, is effectively realized with the help of background scalar
defects. As a result the branons acquire masses, whereas the ratio of Higgs and
fermion (presumably top-quark) masses can be reduced towards the values
compatible with the present-day phenomenology. Since the branons do not couple
to fermions and the Higgs bosons do not decay into branons, the latter ones are
essentially sterile and stable, what makes them the natural candidates for the
dark matter in the Universe.Comment: 34 pages, 2 figures, JHEP style,few important refs. adde
- …