arXiv subjects
Publications and source records attributed to R. Escribano.
We study the lensing of neutrinos by astrophysical objects. At the difference of photons, neutrinos can cross a stellar core; as a result the lens quality improves. While Saturnians alone would benefit from this effect in the Sun, similar effects could be considered for binary systems.
A phenomenological analysis on various decay processes is performed using an energy-dependent $η-η'$ mixing angle scheme. Special attention is given to the radiative couplings between lowest-lying vector and pseudoscalar mesons. The agreement between our predictions and the experimental values is remarkable. This analysis opens a connection to two-angle fits in the $η-η'$ sector.
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.
Central pseudoscalar production in $pp$ scattering is suppressed at small values of $Q_\perp$. Such a behavior is expected if the production occurs through the fusion of two vectors. We argue that an extension of the experiment could probe the gluon contribution to the proton spin.
The value of the $η- η'$ mixing angle $θ_P$ 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, $J/ψ$ decays into a vector and a pseudoscalar meson, and other transitions. A value of $θ_P$ between $-17^\circ$ and $-13^\circ$ is consistent with all the present experimental evidence and the average $θ_P=-15.5^\circ\pm 1.3^\circ$ seems to be favoured.
Central pseudoscalar production in $pp$ scattering is suppressed at small values of $Q_\perp$, where $Q$ is defined as the difference between the momenta transferred from the two protons. Such a behaviour is expected if the production occurs through the fusion of two vectors. Photon exchange could provide the dominant contribution at low transferred momenta, but we argue that an extension of the experiment could probe the gluon contribution to the proton spin.
The octet-singlet mixing angle $θ_P$ in the pseudoscalar meson nonet is deduced from the rich set of accurate data on $J/ψ$ decays into a vector and a pseudoscalar meson. Corrections due to non-ideal $ω$-$ϕ$ mixing have been included for the first time and turn out to be crucial to find $θ_P = -16.9 \pm 1.7$ degrees, which is appreciably less negative than previous results coming from similar analyses.
The discrepancy between the experimental decay rate of orthopositronium (o-Ps) and the QED theoretical prediction can be solved by invoking decays of o-Ps into exotic particles with branching ratios of the order of 10^{-3}. We show that considerations based on primordial nucleosynthesis and effective Lagrangians place a very stringent upper bound: B = Gamma(o-Ps -> ``exotic'' + ...)/Gamma(o-Ps) <= 2 x 10^{-15}, ruling out the exotic decay solution to the puzzle.
The effective Lagrangian approach allows us to constrain fermion magnetic and electric moments using LEP-I data. We improve some of the previous limits on these moments.