Neutrino masses in RPV models with two pairs of Higgs doublets

We study the generation of neutrino masses and mixing in supersymmetric R-parity violating models containing two pairs of Higgs doublets. In these models, new RPV terms $\hat H_{D_1} \hat H_{D_2} \hat E$ arise in the superpotential, as well as new soft terms. Such terms give new contributions to neutrino masses. We identify the different parameters and suppression/enhancement factors that control each of these contributions. At tree level, just like in the MSSM, only one neutrino acquires a mass due to neutrino-neutralino mixing. There are no new one loop effects. We study the two loop contributions and find the conditions under which they can be important.Comment: 22 pages, 5 figures, 3 appendice

The two-photon exchange contribution to muonic hydrogen from chiral perturbation theory

We compute the spin-dependent and spin-independent structure functions of the forward virtual-photon Compton tensor of the proton at one loop using heavy baryon effective theory including the Delta particle. We compare with previous results when existing. Using these results we obtain the leading hadronic contributions, associated to the pion and Delta particles, to the Wilson coefficients of the lepton-proton four fermion operators in NRQED. The spin-independent coefficient yields a pure prediction for the two-photon exchange contribution to the muonic hydrogen Lamb shift, $\Delta E_{\rm TPE}(\pi\&\Delta)=34(13)$ $\mu$eV. We also compute the charge, $\langle r^n \rangle$, and Zemach, $\langle r^n \rangle_{(2)}$, moments for $n \geq 3$. Finally, we discuss the spin-dependent case, for which we compute the difference between the four-fermion Wilson coefficients relevant for hydrogen and muonic hydrogen.Comment: 43 pages, 6 figures. Minor corrections, references added, misprints corrected, Eq. (3.19) added, results unchanged. To meet journal versio

The Lamb shift in muonic hydrogen and the proton radius from effective field theories

We comprehensively analyse the theoretical prediction for the Lamb shift in muonic hydrogen, and the associated determination of the proton radius. We use effective field theories. This allows us to relate the proton radius with well-defined objects in quantum field theory, eliminating unnecessary model dependence. The use of effective field theories also helps us to organize the computation so that we can clearly state the parametric accuracy of the result. In this paper we review all (and check several of) the contributions to the energy shift of order $\alpha^5$, as well as those that scale like $\alpha^6\times$logarithms in the context of non-relativistic effective field theories of QED.Comment: 34 pages, 8 figures, 1 table, 1 appendix. Minor corrections, references added. Replaced to meet journal versio

Model-independent determination of the two-photon exchange contribution to hyperfine splitting in muonic hydrogen

We obtain a model-independent prediction for the two-photon exchange contribution to the hyperfine splitting in muonic hydrogen. We use the relation of the Wilson coefficients of the spin-dependent dimension-six four-fermion operator of NRQED applied to the electron-proton and to the muon-proton sectors. Their difference can be reliably computed using chiral perturbation theory, whereas the Wilson coefficient of the electron-proton sector can be determined from the hyperfine splitting in hydrogen. This allows us to give a precise model-independent determination of the Wilson coefficient for the muon-proton sector, and consequently of the two-photon exchange contribution to the hyperfine splitting in muonic hydrogen, which reads $\delta \bar E_{p\mu,\rm HF}^{\rm TPE}(nS)=-\frac{1}{n^3}1.161(20)$ meV. Together with the associated QED analysis, we obtain a prediction for the hyperfine splitting in muonic hydrogen that reads $E^{\rm th}_{p\mu,\rm HF}(1S)=182.623(27)$ meV and $E^{\rm th}_{p\mu,\rm HF}(2S)=22.8123(33)$ meV. The error is dominated by the two-photon exchange contribution.Comment: 18 pages, 4 figures, 3 tables. v2: Minor corrections to meet journal version, references adde

P-wave heavy quarkonium spectrum with next-to-next-to-next-to-leading logarithmic accuracy

We compute the heavy quarkonium mass of $l\not= 0$ (angular momentum) states, with otherwise arbitrary quantum numbers, with next-next-to-next-to-leading logarithmic (N$^3$LL) accuracy. This constitutes the first observable in heavy quarkonium for which two orders of the weak-coupling expansion sensitive to the ultrasoft scale are known and the resummation of ultrasoft logarithms is made. We also obtain, for the first time, resummed N$^3$LL expressions for the different fine and hyperfine energy splittings of these states, which are not sensitive to the ultrasoft scale but still require resummation of (hard) logarithms. We do this analysis for the equal and non-equal mass cases. We also study an alternative computational scheme that treats the static potential exactly. We then perform a comprehensive phenomenological analysis: we apply these results to the $n=2$, $l=1$ bottomonium, $B_c$ and charmonium systems and study their convergence.Comment: 49 pages, 15 figures, 1 tabl

Current and future perspectives of positronium and muonium spectroscopy as dark sectors probe

Positronium and Muonium are purely leptonic atoms and hence free of an internal sub-structure. This qualifies them as potentially well suited systems to probe the existence of physics beyond the Standard Model. We hence carry out a comprehensive study of the sensitivity of current Positronium and Muonium precision spectroscopy to several new physics scenarios. By taking properly into account existing experimental and astrophysical probes, we define clear experimental targets to probe new physics via precise spectroscopy. For Positronium we find that, in order for the spectroscopy bounds to reach a sensitivity comparable to the electron gyromagnetic factor, an improvement of roughly five orders of magnitude from state-of-the-art precision is required, which would be a challenge based on current technology. More promising is instead the potential reach of Muonium spectroscopy: in the next few years experiments like Mu-MASS at PSI will probe new regions of the parameter space testing the existence of medium/short range (MeV and above) spin-dependent and spin-independent dark forces between electrons and muons.Comment: 8 pages, 6 figures. Version changed to match journal version. Figures update

El Bullying: análisis de la acción preventiva

Los actos violentos entre iguales son situaciones que han sucedido a lo largo de los siglos, aunque, hasta hace unos escasos años no se mostró gran preocupación por estos actos. En la actualidad, es un hecho que se tiene en verdadera consideración y que causa una gran inquietud. Este fenómeno ocasiona terribles consecuencias tanto físicas, pero, sobre todo, psicológicas en todo aquel niño/a que lo padece o lo lleva a cabo incluso en el resto de los compañeros/as y en la sociedad en general. En este trabajo, en la primera parte, se hace un breve, pero exhaustivo análisis de todos los aspectos sobre el fenómeno “Bullying”. El foco de interés se sitúa en la importancia de la prevención y la cooperación con las familias para combatir y erradicar estos actos y relaciones negativas. En la segunda parte, se muestra una detallada formación para las y los docentes que se basa en la importancia del conocimiento de la información sobre este fenómeno, la detección y la intervención y, en especial, en la prevención mediante la educación emocional, el trabajo cooperativo y la buena coordinación y cooperación entre las familias y la escuela. Así como del fomento y promulgación del nuevo Sistema Educativo Inclusivo junto a sus técnicas y metodologías. Finalmente, se concluye destacando que el Acoso Escolar es un gran problema para el futuro de la sociedad. Estos actos influyen negativamente en cada uno de los alumnos/as por lo que se debe erradicar y la mejor manera para conseguirlo es que los docentes dispongan de una completa y significativa formación.<br /