6,308 research outputs found
Circular Symmetry in Topologically Massive Gravity
We re-derive, compactly, a TMG decoupling theorem: source-free TMG separates
into its Einstein and Cotton sectors for spaces with a hypersurface-orthogonal
Killing vector, here concretely for circular symmetry. We can then generalize
it to include matter, which is necessarily null.Comment: amplified published versio
Semileptonic decays of pseudoscalar mesons to scalar "f_0" meson
The transition form factors of (D_s -> f_0 l nu), (D -> f_0 l nu) and (B_u ->
f_0 l nu) decays are calculated in 3-point QCD sum rule method, assuming that
"f_0" is a quark-antiquark state with a mixture of strange and light quarks.
The branching ratios of these decays are calculated in terms of the mixing
angle.Comment: 12 pages, 4 figures, LaTeX formatte
Unitary Structure of the QCD Sum Rules and KYN and KY\Xi Couplings
New relations between QCD Borel sum rules for strong coupling constants of
K-mesons to baryons are derived. It is shown that starting from the sum rule
for the coupling constants and it
is straightforward to obtain corresponding sum rules for the , couplings, .Comment: 7 pages, 2 tables, International Workshop on Quantum
Chromodynamics:Theory and Experiment, QCD@Work-2005, Coversano(Bari, Italy),
16-20 June, 200
The complete set of solutions of the geodesic equations in the space-time of a Schwarzschild black hole pierced by a cosmic string
We study the geodesic equations in the space-time of a Schwarzschild black
hole pierced by an infinitely thin cosmic string and give the complete set of
analytical solutions of these equations for massive and massless particles,
respectively. The solutions of the geodesic equations can be classified
according to the particle's energy and angular momentum, the ratio between the
component of the angular momentum aligned with the axis of the string and the
total angular momentum, the deficit angle of the space-time and as well the
horizon radius (or mass) of the black hole. For bound orbits of massive test
particles we calculate the perihelion shift, we discuss light deflection and
comment on the Newtonian limit.Comment: 21 pages; section 3 shortened, references added; accepted for
publication in Phys. Rev.
Light vector meson octet-decuplet baryon vertices in QCD
The strong coupling constants between light vector mesons and octet-decuplet
baryons are calculated in framework of the light cone QCD sum rules, taking
into account SU(3) flavor symmetry breaking effects. It is shown that all
strong coupling constants can be represented in terms of a single universal
function. Size of the SU(3) symmetry breaking effects are estimated.Comment: 27 pages, 6 figures, LaTeX formatte
Vector meson dominance and radiative decays of heavy spin-3/2 baryons to heavy spin--1/2 baryons
Using the calculated values of the strong coupling constants of the heavy
sextet spin-3/2 baryons to sextet and antitriplet heavy spin-1/2 baryons with
light mesons within the light cone QCD sum rules method, and vector meson
dominance assumption, the radiative decay widths are calculated. These widths
are compared with the "direct" radiative decay widths predicted in the
framework of the light cone QCD sum rules.Comment: 8 pages, no figures, LaTeX formatte
Lepton polarization correlations in
In this work we will study the polarizations of both leptons () in the
decay channel . In the case of the dileptonic inclusive
decay , where apart from the polarization asymmetries
of single lepton , one can also observe the polarization asymmetries of
both leptons simultaneously. If this sort of measurement is possible then we
can have, apart from decay rate, FB asymmetry and the six single lepton
polarization asymmetries (three each for and ), nine more
double polarization asymmetries. This will give us a very useful tool in more
strict testing of SM and the physics beyond. We discuss the double polarization
asymmetries of leptons in the decay mode within
the SM and the Minimal Supersymmetric extensions of it.Comment: 21 pages, 21 figures; version to match paper to appear in PR
Instabilities for a relativistic electron beam interacting with a laser irradiated plasma
The effects of a radiation field (RF) on the unstable modes developed in
relativistic electron beam--plasma interaction are investigated assuming that
, where is the frequency of the RF and
is the plasma frequency. These unstable modes are parametrically
coupled to each other due to the RF and are a mix between two--stream and
parametric instabilities. The dispersion equations are derived by the
linearization of the kinetic equations for a beam--plasma system as well as the
Maxwell equations. In order to highlight the effect of the radiation field we
present a comparison of our analytical and numerical results obtained for
nonzero RF with those for vanishing RF. Assuming that the drift velocity
of the beam is parallel to the wave vector of the
excitations two particular transversal and parallel configurations of the
polarization vector of the RF with respect to are
considered in detail. It is shown that in both geometries resonant and
nonresonant couplings between different modes are possible. The largest growth
rates are expected at the transversal configuration when is
perpendicular to . In this case it is demonstrated that in general
the spectrum of the unstable modes in -- plane is split into two
distinct domains with long and short wavelengths, where the unstable modes are
mainly sensitive to the beam or the RF parameters, respectively. In parallel
configuration, , and at short wavelengths
the growth rates of the unstable modes are sensitive to both beam and RF
parameters remaining insensitive to the RF at long wavelengths.Comment: 23 pages, 5 figure
Semileptonic Decay of and From QCD Sum Rule
We calculate , and to transition form
factors, and study semileptonic decays of and based on QCD sum rule. Measuring these semileptonic decays with
high statistics will give valuable information on the nature of light scalar
mesons.Comment: 13 pages, 5 figures,latex,typos and errors correcte
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