4,148 research outputs found
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
Tensor mesons produced in tau lepton decays
Light tensor mesons (T = a_2, f_2 and K_2^*) can be produced in decays of tau
leptons. In this paper we compute the branching ratios of tau --> T pi nu
decays by assuming the dominance of intermediate virtual states to model the
form factors involved in the relevant hadronic matrix element. The exclusive
f_2(1270) pi^- decay mode turns out to have the largest branching ratio, of
O(10^-4) . Our results indicate that the contributions of tensor meson
intermediate states to the three-pseudoscalar channels of tau decays are rather
small.Comment: 10 pages, 1 figure. Version accepted for publication in PRD, some
typos are corrected and comments are added in section 4. Conclusions remain
unchange
Pseudospectral versus finite-differences schemes in the numerical integration of stochastic models of surface growth
We present a comparison between finite differences schemes and a
pseudospectral method applied to the numerical integration of stochastic
partial differential equations that model surface growth. We have studied, in
1+1 dimensions, the Kardar, Parisi and Zhang model (KPZ) and the Lai, Das Sarma
and Villain model (LDV). The pseudospectral method appears to be the most
stable for a given time step for both models. This means that the time up to
which we can follow the temporal evolution of a given system is larger for the
pseudospectral method. Moreover, for the KPZ model, a pseudospectral scheme
gives results closer to the predictions of the continuum model than those
obtained through finite difference methods. On the other hand, some numerical
instabilities appearing with finite difference methods for the LDV model are
absent when a pseudospectral integration is performed. These numerical
instabilities give rise to an approximate multiscaling observed in the
numerical simulations. With the pseudospectral approach no multiscaling is seen
in agreement with the continuum model.Comment: 13 single column pages, RevTeX, 6 eps fig
Caracterización del significado de múltiplo por maestros en formación
Este trabajo forma parte de una investigación centrada en la divisibilidad en Z+. Los sujetos participantes son maestros en formación. Uno de los objetivos de la investigación consiste en caracterizar los significados que muestran los maestros en formación sobre el concepto de múltiplo. Este artículo recoge los resultados obtenidos en relación con dicho objetivo. Analizamos las producciones escritas de 37 maestros en formación obtenidas en una sesión práctica de aula, diseñada y desarrollada en el contexto de un experimento de enseñanza. Realizamos la caracterización de los significados a través de los elementos del análisis didáctico: estructura conceptual, sistemas de representación y fenomenología. Los maestros en formación mostraron mayoritariamente tres significados de múltiplo: producto, relación y dividendo en una división exacta
The genetic properties of homosexual copulation behaviour in Tribolium castaneum: artificial selection
International audienc
Significados de las relaciones "ser múltiplo" y "ser divisor" mostradas por maestros de educación primaria en formación
Este trabajo forma parte de una investigación en desarrollo sobre divisibilidad, como conocimiento matemático, de maestros de educación primaria en formación. Presentamos algunos resultados sobre dos relaciones consideradas: “ser múltiplo” y “ser divisor”. Analizamos las producciones de 104 futuros maestros en una prueba escrita, para delimitar diferentes significados que ponen de manifiesto de estas relaciones. Mostramos ejemplos de los diferentes significados. Los futuros maestros no utilizaron el término “relación” en sus respuestas. Mayoritariamente, se basaron en operaciones aritméticas, con predominio de producto y división
Gauge invariance and finite width effects in radiative two-pion tau lepton decay
The contribution of the rho^{\pm} vector meson to the tau -> pi pi nu gamma
decay is considered as a potential source for the determination of the magnetic
dipole moment of this light vector meson. In order to keep gauge-invariance of
the whole decay amplitude, a procedure similar to the fermion loop-scheme for
charged gauge bosons is implemented to incorporate the finite width effects of
the rho^{\pm} vector meson. The absorptive pieces of the one-loop corrections
to the propagators and electromagnetic vertices of the rho^{\pm} meson and
W^{\pm} gauge boson have identical forms in the limit of massless particles in
the loops, suggesting this to be a universal feature of spin-one unstable
particles. Model-dependent contributions to the tau -> pi pi nu gamma decay are
suppressed by fixing the two-pion invariant mass distribution at the rho meson
mass value. The resulting photon energy and angular distribution is relatively
sensitive to the effects of the rho magnetic dipole moment.Comment: 22 pages, 4 postscript figures, references and comments on relevance
of perturbative treatment of rho electromagnetic vertex are added, accepted
for pub. in Phys. Rev.
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