On the gluon content of the eta and eta' mesons

A phenomenological analysis of radiative $V\to P\gamma$ and $P\to V\gamma$ decays is performed with the purpose of determining the gluonic content of the $\eta$ and $\eta^\prime$ wave functions. Our results show that within our model there is no evidence for a gluonium contribution in the $\eta$, $Z_\eta^2=0.00\pm 0.12$, or the $\eta^\prime$, $Z_{\eta^\prime}^2=0.04\pm 0.09$. In terms of a mixing angle description this corresponds to $\phi_P=(41.4\pm 1.3)^\circ$ and $|\phi_{\eta^\prime G}|=(12\pm 13)^\circ$. In addition, the $\eta$-$\eta^\prime$ mixing angle is found to be $\phi_P=(41.5\pm 1.2)^\circ$ if we don't allow for a gluonium component.Comment: 16 pages, 3 figures, JHEP style. First part of data fitting changed, conclusions not modifie

The ratio Phi->K+K-/K0K0bar

The ratio Phi->K+K-/K0K0bar is discussed and its present experimental value is compared with theoretical expectations. A difference larger than two standard deviations is observed. We critically examine a number of mechanisms that could account for this discrepancy, which remains unexplained. Measurements at DAPHNE at the level of the per mille accuracy can clarify whether there exist any anomaly.Comment: 16 page

Evolución de la Estructura de Mercado de las Telecomunicaciones en España.

El sector de las telecomunicaciones ha experimentado un importante cambio estructural durante los últimos cuatro años, tanto en los aspectos regulatorios como de mercado. La razón, sin duda, está en el cambio tecnológico y de mentalidad que ha permitido la liberalización y globalización de los mercados. En este artículo se da una visión panorámica de los aspectos regulatorios a lo largo del siglo XX en España y se analiza más en detalle la evolución de la estructura de mercado durante los últimos cuatro años, haciendo especial hincapié en la delicada situación de las decisiones de inversión (redes, licencias, etc.) tomadas por los operadoresSector de las telecomunicaciones en España; Estructura del mercado de las telecomunicaciones;

Pseudoscalar mixing in J/psi and psi(2S) decay

Based on the branching fractions of J/psi(psi(2S))-> VP from different collaborations, the pseudoscalar mixing is extensively discussed with a well established phenomenological model. The mixing angle is determined to be -14 degree by fitting to the new world average if only quark content is considered. After taking into account the gluonic content in eta and eta prime simultaneously, the investigation shows that eta favors only consisting of light quarks, while the gluonic content of eta prime is Z_{eta prime}^2=0.30\pm0.24.Comment: 8 page

Evolución de la Estructura de Mercado de las Telecomunicaciones en España

El sector de las telecomunicaciones ha experimentado un importante cambio estructural durante los últimos cuatro años, tanto en los aspectos regulatorios como de mercado. La razón, sin duda, está en el cambio tecnológico y de mentalidad que ha permitido la liberalización y globalización de los mercados. En este artículo se da una visión panorámica de los aspectos regulatorios a lo largo del siglo XX en España y se analiza más en detalle la evolución de la estructura de mercado durante los últimos cuatro años, haciendo especial hincapié en la delicada situación de las decisiones de inversión (redes, licencias, etc.) tomadas por los operadoresPublicad

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

Composition of the Pseudoscalar Eta and Eta' Mesons

The composition of the eta and eta' mesons has long been a source of discussion and is of current interest with new experimental results appearing. We investigate what can be learnt from a number of different processes: V to P gamma and P to V gamma (V and P are light vector and pseudoscalar mesons respectively), P to gamma gamma, J/psi,psi' to P gamma, J/psi,psi' to P V, and chi_{c0,2} to PP. These constrain the eta-eta' mixing angle to a consistent value, phi approx 42 degrees; we find that the c cbar components are lesssim 5% in amplitude. We also find that, while the data hint at a small gluonic component in the eta', the conclusions depend sensitively on unknown form factors associated with exclusive dynamics. In addition, we predict BR(psi' to eta' gamma) approx 1 10^{-5} and BR(chi_{c0} to eta eta') approx 2 10^{-5} - 1 10^{-4}. We provide a method to test the mixing using chi_{c2} to eta eta, eta' eta', and eta eta' modes and make some general observations on chi_{c0,2} decays. We also survey the semileptonic and hadronic decays of bottom and charmed mesons and find some modes where the mixing angle can be extracted cleanly with the current experimental data, some where more data will allow this, and some where a more detailed knowledge of the different amplitudes is required.Comment: 34 pages, 11 figures. v2: version published in JHEP, added substantial section on B and D meson electroweak decays, added comment on psi' to eta(')/eta_c gamma, Figs 5 and 6 split and made clearer, added references, other minor revisions which don't change conclusion

Large N(c′)_(c'), chiral approach to M(n′)_(n') at finite temperature

We study the temperature dependence of the eta and eta[prime] meson masses within the framework of U(3)L×U(3)R chiral perturbation theory, up to next-to-leading order in a simultaneous expansion in momenta, quark masses and number of colors. We find that both masses decrease at low temperatures, but only very slightly. We analyze higher order corrections and argue that large Nc suggests a discontinuous drop of Meta[prime] at the critical temperature of deconfinement Tc, consistent with a first order transition to a phase with approximate U(1)A symmetry