One pion production in neutrino-nucleon scattering and the different parametrizations of the weak N→ΔN\rightarrow\Delta vertex

The $N \to \Delta$ weak vertex provides an important contribution to the one pion production in neutrino-nucleon and neutrino-nucleus scattering for $\pi N$ 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 $N \to \Delta$ vertex and form factors (FF) and we study their effects on the determination of the axial coupling $C_5^A(0)$, the common normalization of the axial FF, which is predicted to hold 1.2 by using the PCAC hypothesis. Predictions for the $\nu_{\mu} p \to \mu^- p\pi^+$ total cross sections within the two approaches, which include the resonant $\Delta^{++}$ 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.