13,420 research outputs found
Beyond the soft photon approximation in radiative production and decay of charged vector mesons
We study the effects of model-dependent contributions and the electric
quadrupole moment of vector mesons in the decays and
. Their interference with the amplitude originating
from the radiation due to electric charges vanishes for photons emitted
collinearly to the charged particle in the final state. This brings further
support to our claim in previous works, that measurements of the photon energy
spectrum for nearly collinear photons in those decays are suitable for a first
measurement of the magnetic dipole moment of charged vector mesons.Comment: 13 pages, 2 eps figures, Latex. Accepted for publication in Journal
of Physics G: Nuclear and Particle Physics(2001
Radiative corrections of to decays
The electromagnetic radiative corrections to the ( is a vector meson and a charged
lepton) decay rates are evaluated using the cutoff method to regularize virtual
corrections and incorporating intermediate resonance states in the real-photon
amplitude to extend the region of validity of the soft-photon approximation.
The electromagnetic and weak form factors of hadrons are assumed to vary
smoothly over the energies of virtual and real photons under consideration. The
cutoff dependence of radiative corrections upon the scale that
separates the long- and short-distance regimes is found to be mild and is
considered as an uncertainty of the calculation. Owing to partial cancellations
of electromagnetic corrections evaluated over the three- and four-body regions
of phase space, the photon-inclusive corrected rates are found to be dominated
by the short-distance contribution. These corrections will be relevant for a
precise determination of the quark mixing angles by testing isospin
symmetry when measurements of semileptonic rates of charged and neutral
mesons at the few percent level become available. For completeness, we also
provide numerical values of radiative corrections in the three-body region of
the Dalitz plot distributions of these decays.Comment: Further comments and two references adde
Tensor interactions and decays
We study the effects of charged tensor weak currents on the
strangeness-changing decays of the lepton. First, we use the available
information on the form factors to obtain BR when the system is produced
in an antisymmetric tensor configuration. Then, we propose a mechanism for the
direct production of the in decays. Using the current
upper limit on this decay we set a bound on the symmetric tensor interactions.Comment: 13 pages, Late
CP violation in semileptonic tau lepton decays
The leading order contribution to the direct CP asymmetry in tau^{+/-} ->
K^{+/-} pi^0 nu_{tau} decay rates is evaluated within the Standard Model. The
weak phase required for CP violation is introduced through an interesting
mechanism involving second order weak interactions, which is also responsible
for tiny violations of the Delta S= Delta Q rule in K_{l3} decays. The
calculated CP asymmetry turns out to be of order 10^{-12}, leaving a large
window for studying effects of non-standard sources of CP violation in this
observable.Comment: 5 pages, 3 figures, version published in Phys.Rev.
One pion production in neutrino-nucleon scattering and the different parametrizations of the weak vertex
The weak vertex provides an important contribution to the one
pion production in neutrino-nucleon and neutrino-nucleus scattering for
invariant masses below 1.4 GeV. Beyond its interest as a tool in neutrino
detection and their background analyses, one pion production in
neutrino-nucleon scattering is useful to test predictions based on the quark
model and other internal symmetries of strong interactions. Here we try to
establish a connection between two commonly used parametrizations of the weak
vertex and form factors (FF) and we study their effects on the
determination of the axial coupling , the common normalization of the
axial FF, which is predicted to hold 1.2 by using the PCAC hypothesis.
Predictions for the total cross sections within
the two approaches, which include the resonant and other
background contributions in a coherent way, are compared to experimental data.Comment: Submitted to Physics Letters
Solvability of the Dirichlet, Neumann and the regularity problems for parabolic equations with H\"older continuous coefficients
We establish the -solvability of Dirichlet, Neumann and regularity
problems for divergence-form heat (or diffusion) equations with
H\"older-continuous diffusion coefficients, on bounded Lipschitz domains in
. This is achieved through the demonstration of invertibility of
the relevant layer-potentials which is in turn based on Fredholm theory and a
new systematic approach which yields suitable parabolic Rellich-type estimates
- …