Search results for "oscillation"
showing 10 items of 1257 documents
Large lepton mixing and supernova 1987A
2000
We reconsider the impact of $\bar\nu_e \leftrightarrow \bar\nu_{\mu,\tau}$ neutrino oscillations on the observed $\bar\nu_e$ signal of supernova SN 1987A. Performing a maximum-likelihood analysis using as fit parameters the released binding energy $\Eb$ and the average neutrino energy $\Ee$, we find as previous analyses that $\bar\nu_e \leftrightarrow \bar\nu_{\mu,\tau}$ oscillations with large mixing angles have lower best-fit values for $\Ee$ than small-mixing angle (SMA) oscillations. Moreover, the inferred value of $\Ee$ is already in the SMA case lower than those found in simulations. This apparent conflict has been interpreted as evidence against the large mixing oscillation solutions…
Physics Reach of Electron-Capture Neutrino Beams
2005
To complete the picture of neutrino oscillations two fundamental parameters need to be measured, theta13 and delta. The next generation of long baseline neutrino oscillation experiments -superbeams, betabeams and neutrino factories- indeed take aim at measuring them. Here we explore the physics reach of a new candidate: an electron-capture neutrino beam. Emphasis is made on its feasibility thanks to the recent discovery of nuclei that decay fast through electron capture, and on the interplay with a betabeam (its closest relative).
Monochromatic neutrino beams
2005
In the last few years spectacular results have been achieved with the demonstration of non vanishing neutrino masses and flavour mixing. The ultimate goal is the understanding of the origin of these properties from new physics. In this road, the last unknown mixing [U-e3] must be determined. If it is proved to be non-zero, the possibility is open for Charge Conjugation-Parity (CP) violation in the lepton sector. This will require precision experiments with a very intense neutrino source. Here a novel method to create a monochromatic neutrino beam, an old dream for neutrino physics, is proposed based on the recent discovery of nuclei that decay fast through electron capture. Such nuclei will…
CP properties of the leptonic sector for majorana neutrinos
1983
Abstract The leptonic sector of the electroweak theory is analyzed for massive Majorana neutrinos. For n generations, the Majorana mass lagrangian is diagonalized using the polar reduction to guarantee physical positive masses independently of the CP properties or the choice of the phases of the fields. When CP invariance holds, the CP eigenvalues of the definite mass neutrino fields are determined without commitment to a particular phase choice. For charged current interactions, we find that the observable CP violating phases can be parametrized a la Kobayashi-Maskawa for the vertec. Extra ( n − 1) relative phases of the massive neutrino fields are significant. The extra phases are observa…
Tri-bimaximal neutrino mixing and neutrinoless double beta decay
2008
We present a tri-bimaximal lepton mixing scheme where the neutrinoless double beta decay rate (bb0v) has a lower bound which correlates with the ratio alpha = Dmsol/Dmatm well determined by current data, as well as with the unknown Majorana CP phase phi12 characterizing the solar neutrino sub-system. For the special value phi12 = pi/2 (opposite CP-sign neutrinos) the bb0v rate vanishes at tree level when Dmsol/Dmatm = 3/80, only allowed at 3 sigma. For all other cases the rate is nonzero, and lies within current and projected experimental sensitivities close to phi12=0. We suggest two model realizations of this scheme in terms of an A4xZ2 and A4xZ4 flavour symmetries.
Neutrino properties and the decay of the lightest supersymmetric particle
2003
Supersymmetry with broken R-parity can explain the neutrino mass squared differences and mixing angles observed in neutrino oscillation experiments. In the minimal model, where R-parity is broken only by bilinear terms, certain decay properties of the lightest supersymmetric particle (LSP) are correlated with neutrino mixing angles. Here we consider charginos, squarks, gluinos and sneutrinos being the LSP and calculate their decay properties in bilinear R-parity breaking supersymmetry. Together with the decays of charged scalars and neutralinos calculated previously this completes the proof that bilinear R-parity breaking as the source of neutrino masses will be testable at future colliders…
Status and implications of neutrino masses: a brief panorama
2015
15 pages.- 10 figures
Atmospheric neutrino anomaly without maximal mixing?
2000
We consider a pattern of neutrino masses in which there is an approximate mass degeneracy between the two mass eigenstates most coupled to the $\nu_\mu$ and $\nu_\tau$ flavour eigenstates. Earth-matter effects can lift this degeneracy and induce an effectively maximal mixing between these two generations. This occurs if $\nu_e$'s contain comparable admixtures of the degenerate eigenstates, even rather small ones. This provides an explanation of the atmospheric neutrino anomaly in which the {\it ab initio} introduction of a large mixing angle is not required. To test this possibility we perform a novel and detailed analysis of the 52 kiloton-year SuperKamiokande data, and we find that in a l…
Concluding talk at NOW 2006
2006
This writeup summarizes the status of neutrino oscillations, including recent fluxes and experimental data, as of summer 2006. A discussion is given on the current status of absolute scale of neutrino mass from tritium, neutrinoless double beta decay and cosmological observations, as well as the prospects for the next generation of experiments, including lepton flavor violation searches, and their theoretical significance.
Fermion masses, leptogenesis, and supersymmetric SO(10) unification
2007
Current neutrino oscillation data indicate the existence of two large lepton mixing angles, while Kobayashi-Maskawa matrix elements are all small. Here we show how supersymmetric SO(10) with extra chiral singlets can easily reconcile large lepton mixing angles with small quark mixing angles within the framework of the successful Fritzsch ansatz. Moreover we show how this is fully consistent with the thermal leptogenesis scenario, avoiding the so-called gravitino problem. A sizeable asymmetry can be generated at relatively low scales. We present our results in terms of the leptonic CP violation parameter that characterizes neutrino oscillations.