Search

The current neutrino experiments provide an opportunity for testing the inverse see-saw mechanism through charged lepton flavor violating processes and neutrinoless double beta decay. Motivated by this, in this paper we study the $\mathbf{S}_{3}\otimes \mathbf{Z}_{2}$ discrete symmetry in the $B-L$ gauge model where the active light neutrino mass matrix comes from the aforementioned mechanism. In this framework, the effect of complex vacuum expectation values of the Higgs doublets on the fermion masses is explored and, under certain assumptions on the Yukawa couplings, we find that the neutrino mixing is controlled by the Cobimaximal pattern, but a sizeable deviation from the charged lepton sector breaks the well known predictions on the atmospheric angle ($45^{\circ}$) and the Dirac CP-violating phase ($-90^{\circ}$). In addition, due to the presence of heavy neutrinos at the $TeV$ scale, charged lepton flavor violation (CLFV) and neutrinoless double beta decay get notable contributions. Analytical formulae for these observables are obtained, and then a numerical calculation allows to fit quite well the lepton mixing for the normal and inverted hierarchies, however, the branching ratios decay values for CLFV disfavors the latter one. Along with this, the region of parameter space for the $m_{ee}$ effective neutrino mass lies below the GERDA bounds for both the normal and inverted hierarchies. On the other hand, with a particular benchmark, the quark mass matrices are found to have textures that allow to fit with great accuracy the CKM mixing matrix., Comment: 37 pages, 10 figures, 3 tables

In this work we explore the possibility of incorporating particle physics motivated scalar fields to the dark matter cosmological model. In this landscape, we consider the classical complex scalar field in a certain region in the parameter space of the model that increases the number of neutrino species $N_{\mathrm{eff}}$, in order to be consistent with the observed abundance of light elements produced at Big Bang Nucleosynthesis (BBN). We perform analyses using one and two scalar fields. We examine the difference between these models and the priors considered at the edges of the cosmic ladder, this with the purpose of studying the impact of such models on the Hubble cosmic flow. In the two scalar field models we explore the possibility of combining an axion and a Higgs-like field as well as a Higgs-like field and the classical field, we show that in the first case there is no set of parameters that allows us to be consistent with $N_\mathrm{eff}$, while in the second case a strong restriction to the set of parameters is obtained. This last restriction is given in terms of a maximum bound of the fraction of Higgs-like field that can be incorporated together with the classical field. Our results could be relevant in the direct dark matter detection programs., Comment: 18 pages, 5 figures. Discussion and references added, version accepted by PhysRevD

We propose a predictive $Q_4$ flavored 2HDM model, where the scalar sector is enlarged by the inclusion of several gauge singlet scalars and the fermion sector by the inclusion of right handed Majorana neutrinos. In our model, the $Q_4$ family symmetry is supplemented by several auxiliary cyclic symmetries, whose spontaneous breaking produces the observed pattern of SM charged fermion masses and quark mixing angles. The light active neutrino masses are generated from an inverse seesaw mechanism at one loop level thanks to a remnant preserved $Z_2$ symmetry. Our model succesfully reproduces the measured dark matter relic abundance and is consistent with direct detection constraints for masses of the DM candidate around $\sim$ 6.3 TeV. Furthermore, our model is also consistent with the lepton and baryon asymmetries of the Universe as well as with the muon anomalous magnetic moment, Comment: Substantial improvement to the overall content of the paper specially in sections regarding dark matter, analysis of fermion and scalar sectors. Detailed explanation of the possible UV completion of the model as well as about the muon electric dipole moment. Discussions enlarged, new figures, references and appendices added. 35 pages. Matches published version in EPJP

We derive the evolution equations for a system of neutrinos interacting among themselves and with a matter background, based upon the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. This theoretical framework gives an (unclosed) set of first-order coupled integro-differential equations governing the evolution of the reduced density matrices. By employing the hierarchy, we first rederive the mean-field evolution equations for the neutrino one-body density matrix associated with a system of neutrinos and antineutrinos interacting with matter and with an anisotropic neutrino background. Then, we derive extended evolution equations to determine neutrino flavor conversion beyond the commonly used mean-field approximation. To this aim we include neutrino-antineutrino pairing correlations to the two-body density matrix. The inclusion of these new contributions leads to an extended evolution equation for the normal neutrino density and to an equation for the abnormal one involving the pairing mean-field. We discuss the possible impact of neutrino-antineutrino correlations on neutrino flavor conversion in the astrophysical and cosmological environments, and possibly upon the supernova dynamics. Our results can be easily generalized to an arbitrary number of neutrino families., Comment: 19 pages, 3 figures, minor corrections, references added

We propose applications of Radioactive Ion Beam facilities to investigate physics beyond the Standard Model. In particular, we focus on the possible measurement of coherent neutrino-nucleus scattering and on a search for sterile neutrinos, by means of a low energy beta-beam with a Lorentz boost factor $\gamma \approx 1$. In the considered setup the collected radioactive ions are sent inside a 4$\pi$ detector. For the first application we provide the number of events associated with neutrino-nucleus coherent scattering, when the detector is filled in with a noble liquid. For the sterile search we consider that the spherical detector is filled in with a liquid scintillator, and that the neutrino detection channel is inverse-beta decay. We provide the exclusion curves for the sterile neutrino mixing parameters, based upon the 3+1 formalism, depending upon the achievable ion intensity. Our results are obtained both from total rates, and including spectral information with binning in energy and in distance. The proposed experiment represents a possible alternative to clarify the current anomalies observed in neutrino experiments., Comment: 9 pages, 6 figures. v2 - added 2 figures

We discuss the linearization of Einstein equations in the presence of a cosmological constant, by expanding the solution for the metric around a flat Minkowski space-time. We demonstrate that one can find consistent solutions to the linearized set of equations for the metric perturbations, in the Lorentz gauge, which are not spherically symmetric, but they rather exhibit a cylindrical symmetry. We find that the components of the gravitational field satisfying the appropriate Poisson equations have the property of ensuring that a scalar potential can be constructed, in which both contributions, from ordinary matter and $\Lambda > 0$, are attractive. In addition, there is a novel tensor potential, induced by the pressure density, in which the effect of the cosmological constant is repulsive. We also linearize the Schwarzschild-de Sitter exact solution of Einstein's equations (due to a generalization of Birkhoff's theorem) in the domain between the two horizons. We manage to transform it first to a gauge in which the 3-space metric is conformally flat and, then, make an additional coordinate transformation leading to the Lorentz gauge conditions. We compare our non-spherically symmetric solution with the linearized Schwarzschild-de Sitter metric, when the latter is transformed to the Lorentz gauge, and we find agreement. The resulting metric, however, does not acquire a proper Newtonian form in terms of the unique scalar potential that solves the corresponding Poisson equation. Nevertheless, our solution is stable, in the sense that the physical energy density is positive., Comment: 7 pages revtex, no figures; discussion on light bending added, no effect on conclusions, version to appear in Physical Review D.

The next generation of long baseline neutrino oscillation experiments will aim at determining the unknown mixing angle $\theta_{13}$, the type of neutrino mass hierarchy and CP-violation. We discuss the separation of these properties by means of the energy dependence of the oscillation probability and we consider an hybrid setup which combines the electron capture and the $\beta^+$ decay from the same radioactive ion with the same boost. We study the sensitivity to the mixing angle and the CP-phase, the CP discovery potential and the reach to determine the type of neutrino mass hierarchy. The analysis is performed for different boosts and baselines. We conclude that the combination of the two decay channels, with different neutrino energies, achieves remarkable results., Comment: 21 pages, 8 figures. Talk given at 13th International Workshop on Neutrino Telescopes, Venice, March 10-13, 2009

The ultimate goal for future neutrino facilities is the determination of CP violation in neutrino oscillations. Besides $| U(e3) | \ne 0$, this will require precision experiments with a very intense neutrino source and energy control. With this objective in mind, the creation of monochromatic neutrino beams from the electron capture decay of boosted ions by the SPS of CERN has been proposed. We discuss the capabilities of such a facility as a function of the energy of the boost and the baseline for the detector. We compare the physics potential for two different configurations: I) $\gamma=90$ and $\gamma=195$ (maximum achievable at present SPS) to Frejus; II) $\gamma=195$ and $\gamma=440$ (maximum achievable at upgraded SPS) to Canfranc. We conclude that the SPS upgrade to 1000 GeV is important to reach a better sensitivity to CP violation iff it is accompanied by a longer baseline. In both Setups, the gain in the CP violation sensitivity with a previous knowledge of $| U(e3) |$ is apparent., Comment: 11 pages, 7 figures

The goal for future neutrino facilities is the determination of the U(e3) mixing and CP violation in neutrino oscillations. This will require precision experiments with a very intense neutrino source and energy control. With this objective in mind, the creation of monochromatic neutrino beams from the electron capture decay of boosted ions by the SPS of CERN has been proposed. We discuss the capabilities of such a facility as a function of the energy of the boost and the baseline for the detector. We conclude that the SPS upgrade to 1000 GeV is crucial to reach a better sensitivity to CP violation iff it is accompanied by a longer baseline. We compare the physics potential for two different configurations: I) $\gamma=90$ and $\gamma=195$ (maximum achievable at present SPS) to Frejus; II) $\gamma=195$ and $\gamma=440$ (maximum achievable at upgraded SPS) to Canfranc. The main conclusion is that, whereas the gain in the determination of U(e3) is rather modest, setup II provides much better sensitivity to CP violation., Comment: 4 pages, 5 figures, To appear in the proceedings of International Europhysics Conference on High Energy Physics (EPS-HEP2007), Manchester, England, 19-25 July 2007

The goal for future neutrino facilities is the determination of the $[U_{e3}]$ mixing and CP violation in neutrino oscillations. This will require precision experiments with a very intense neutrino source. With this objective the creation of neutrino beams from the radioactive decay of boosted ions by the SPS of CERN from either beta or electron capture transitions has been propossed. We discuss the capabilities of such facilities as a function of the energy of the boost and the baseline for the detector. We conclude that the SPS upgrade to 1000 GeV is crucial to have a better sensitivity to CP violation if it is accompanied by a longer baseline. We compare the physics potential for two different configurations. In the case of beta beams, with the same boost for both $\beta^+$ (neutrinos) and $\beta^-$ (antineutrinos), the two setups are: I) $\gamma=120$, L=130 Km (Frejus); II) $\gamma=330$, L=650 Km (Canfranc). In the case of monochromatic EC beams we exploit the energy dependence of neutrino oscillations to separate out the two parameters $U(e3)$ and the CP phase $\delta$. Setup I runs at $\gamma=90$ and $\gamma=195$ (maximum achievable at present SPS) to Frejus, whereas Setup II runs at $\gamma=195$ and $\gamma=440$ (maximum achievable at upgraded SPS) to Canfranc. The main conclusion is that, whereas the gain in the determination of $U(e3)$ is rather modest, setup II provides much better sensitivity to CP violation., Comment: 6 pages, 10 figures, Proceedings of LHC LUMI 2006 CARE-HHH-AP Wokshop, October 2006, Valencia

The goal for future neutrino facilities is the determination of the $[U_{e3}]$ mixing and CP violation in neutrino oscillations. This will require precision experiments with a very intense neutrino source. Here a novel method to create a monochromatic neutrino beam based on the recent discovery of nuclei that decay fast through electron capture is discussed. The boost of such radioactive ions will generate a monochromatic directional neutrino beam when decaying at high energy in a storage ring with long straight sections. We show that the capacity of such a facility to discover new physics is impressive, so that the principle of energy dependence in the oscillation probability of the $\nu_e \to \nu_{\mu}$ channel is operational to separate out the two parameters of the mixing $\theta_{13}$ and of the CP-violating phase $\delta$., Comment: 16 pages, 7 figures, Proc. 3rd. International Workshop on NO-VE: Neutrino Oscillations in Venice, 7-10 February 2006, Venice