The η−η′\eta - \eta' Mixing Angle Revisited

The value of the $\eta - \eta'$ mixing angle $\theta_P$ is phenomenologically deduced from a rather exhaustive and up-to-date analysis of data including strong decays of tensor and higher-spin mesons, electromagnetic decays of vector and pseudoscalar mesons, $J/\psi$ decays into a vector and a pseudoscalar meson, and other transitions. A value of $\theta_P$ between $-17^\circ$ and $-13^\circ$ is consistent with all the present experimental evidence and the average $\theta_P=-15.5^\circ\pm 1.3^\circ$ seems to be favoured.Comment: 17 pages, LaTeX. 2 references added, some comments on Chiral Perturbation Theor

Mixing of eta-eta' Mesons in J/psi Decays into a Vector and a Pseudoscalar Meson

The octet-singlet mixing angle $\theta_P$ in the pseudoscalar meson nonet is deduced from the rich set of accurate data on $J/\psi$ decays into a vector and a pseudoscalar meson. Corrections due to non-ideal $\omega$-$\phi$ mixing have been included for the first time and turn out to be crucial to find $\theta_P = -16.9 \pm 1.7$ degrees, which is appreciably less negative than previous results coming from similar analyses.Comment: 9 pages, LaTeX, full postscript file available via anonymous ftp at ftp://ftp.ifae.es/preprint/ft/uabft412.p

Asymmetric and time-varying error-correction: an application to labour demand in the UK

In this paper we compare the asymmetric and time-varying error-correction models that have recently been proposed, and apply these to the case of UK aggregate labour demand. The aim of the paper is to investigate the possible co-existence of time-varying adjustment on the one hand, and constant asymmetric error-correction on the other hand. We find that without allowing for time-varying adjustment variables, the asymmetric error-correction models of Granger and Lee (1989) and Escribano (1986) work well. But once the time-varying adjustment variables are included, the evidence for time-invariant asymmetric adjustment is marginal

Scalar and vector meson exchange in V->P0P0gamma decays

The scalar contributions to the radiative decays of light vector mesons into a pair of neutral pseudoscalars, $V\to P^0P^0\gamma$, are studied within the framework of the Linear Sigma Model. This model has the advantage of incorporating not only the scalar resonances in an explicit way but also the constraints required by chiral symmetry. The experimental data on $\phi\to\pi^0\pi^0\gamma$, $\phi\to\pi^0\eta\gamma$, $\rho\to\pi^0\pi^0\gamma$ and $\omega\to\pi^0\pi^0\gamma$ are satisfactorily accommodated in our framework. Theoretical predictions for $\phi\to K^0\bar K^0\gamma$, $\rho\to\pi^0\eta\gamma$, $\omega\to\pi^0\eta\gamma$ and the ratio $\phi\to f_0\gamma/a_0\gamma$ are also given.Comment: 42 pages, 11 figures. A new paragraph explaining the seminal contribution of Ref. [19] is adde

Bell's inequality tests: from photons to B-mesons

We analyse the recent claim that a violation of a Bell's inequality has been observed in the $B$--meson system [A. Go, {\em Journal of Modern Optics} {\bf 51} (2004) 991]. The results of this experiment are a convincing proof of quantum entanglement in $B$--meson pairs similar to that shown by polarization entangled photon pairs. However, we conclude that the tested inequality is not a genuine Bell's inequality and thus cannot discriminate between quantum mechanics and local realistic approaches.Comment: 5 page

Boron abundance and solar neutrino spectrum distortion

The presence of neutrinos from Boron decay in the flux observed on Earth is attested by the observation of their energy spectrum. Possible distortions of the spectrum investigated in current detectors are often interpreted in terms of evidence in favour or against various schemes of neutrino oscillations. We stress here that a distortion of the spectrum at high energies could also result from an increase in the ratio of neutrinos originating from ($^3$He+p) and $^8$B reactions. While a $^8$B neutrino depletion would contribute to this effect, an increase in the Hep contribution seems also needed to reproduce the preliminary data.Comment: 8 pages, 2 figures; abstract and introduction rewritten to match the conclusions bette

Using a free open source software to teach mathematics

We present the experience of the authors teaching mathematics to freshmen engineering students with the help of the open source computer algebra system Sage. We describe some teaching resources and present an ad hoc distribution of Sage used by the authors

A model free cointegration approach for pairs of I(d) variables

In this paper we propose several model free (non parametric) statistics to measure serial dependence that are useful to characterize the short and the long memory properties of series in the time and the frequency domain. Conditions on the joint memory properties of the series such as cointegration are introduced by means of these statistics. We show that the relationship between the non parametric concept of cointegration and the cross-covariance functions of the series, has a natural interpretation as an instrumental variable estimator. We show that its small sample behavior is better than the usual least squares estimator. Finally, from our characterization it is posibble to discriminate between fractional and integer cointegratio