Search results for "Measurements"
showing 10 items of 720 documents
Combining first KamLAND results with solar neutrino data
2002
We consider the impact of the recent KamLAND data on neutrino oscillations, the first terrestrial neutrino experiment that can probe the solar neutrino anomaly. By combining the first 145.1 days of KamLAND data with the full sample of latest solar neutrino data we find an enhanced rejection against non-LMA oscillations, allowed only at more than 4 sigma with respect to LMA. Furthermore, the new data have a strong impact in narrowing down the allowed range of Delta_m^2 inside the LMA region. In contrast, our global analysis indicates that the new data have little impact on the location of the best fit point. In particular the solar neutrino mixing remains significantly non-maximal (3 sigma).
Direct neutrino mass measurements
1995
The paper reports on recent progress and developments since the neutrino '92 conference in the search for finite neutrino masses by direct mass measurements. Regarding the mass of μ - and τ -neutrino experiments have been finished and come up with somewhat improved upper bounds; the negative m 2 -value for the μ -neutrino could be removed mostly. Indications of a 17 keV neutrino component in β -decay spectra have been disproved by a number of alternative experiments as well as by reanalysis of part of the original data. Regarding the electron neutrino mass, measurements by magnetic spectrometers are phasing out in favour of electrostatic filters with magnetic guiding fields. These experimen…
Probing a Supersymmetric Model for Neutrino Masses at Ultrahigh Energy Neutrino Telescopes
2008
A bilinear R-Parity breaking SUSY model for neutrino mass and mixing predicts the lightest superparticle to decay mainly into a pair of tau leptons or b quarks along with a neutrino for relatively light SUSY spectra. This leads to a distinctive triple bang signature of SUSY events at ultrahigh energy neutrino telescopes like IceCube or Antares. While the expected signal size is only marginal at IceCube, it will be promising for a future multi-km^3 size neutrino telescope.
Neutrino masses and mixings from supersymmetry with bilinear R-parity violation: A theory for solar and atmospheric neutrino oscillations
2000
The simplest unified extension of the MSSM with bi-linear R--Parity violation naturally predicts a hierarchical neutrino mass spectrum, in which one neutrino acquires mass by mixing with neutralinos, while the other two get mass radiatively. We have performed a full one-loop calculation of the neutralino-neutrino mass matrix in the bi-linear \rp MSSM, taking special care to achieve a manifestly gauge invariant calculation. Moreover we have performed the renormalization of the heaviest neutrino, needed in order to get meaningful results. The atmospheric mass scale and maximal mixing angle arise from tree-level physics, while solar neutrino scale and oscillations follow from calculable one-lo…
Neutrino masses and mixing: 2008 status
2009
We review the current status (as of the end of 2008) of neutrino mass and mixing determinations, focusing on the hints of θ 13 > 0 , recently emerged in our global analysis.
Neff versus the lightest neutrino mass
2016
AbstractWithin the framework of low-scale Type I seesaw models with two and three extra sterile neutrinos we evaluate the production of the sterile states in the Early Universe. We explore the full parameter space and find that in the model with two extra states both of them reach thermal equilibrium with the primordial plasma. In the model with three sterile neutrinos, if the lightest active neutrino mass is below O(10−3eV) one sterile neutrino might not thermalize, while the other two always reach thermalization. Applying constrains from both extra radiation at BBN and CMB, and the dark matter allowed abundance, we show that the spectra of heavier states are severely restricted in the mas…
N_eff in low-scale seesaw models versus the lightest neutrino mass
2014
We evaluate the contribution to $N_{\rm eff}$ of the extra sterile states in low-scale Type I seesaw models (with three extra sterile states). We explore the full parameter space and find that at least two of the heavy states always reach thermalisation in the Early Universe, while the third one might not thermalise provided the lightest neutrino mass is below ${\mathcal O}(10^{-3}$eV). Constraints from cosmology therefore severely restrict the spectra of heavy states in the range 1eV- 100 MeV. The implications for neutrinoless double beta decay are also discussed.
Neutrino masses and cosmology: current bounds and future sensitivities
2005
After a short introduction on the predicted cosmic neutrino background, we review the connection between neutrino masses and cosmology. We show how a combined analysis of data from the anisotropies of the cosmic microwave background radiation and from the distribution of cosmological large-scale structure gives a bound on the sum of neutrino masses. We briefly discuss the sensitivity of future cosmological data to neutrino masses.
Reconciling dark matter and solar neutrinos
1993
Abstract We present a simple model for neutrino dark matter in which neutrino masses arise radiatively and the solar neutrino data are explained via the MSW effect. The dark matter scale arises at the one-loop level with the MSW scale arises only in two loops. The model is compatible with all observational facts and allows observable ν e ν τ or ν μ ν τ oscillation rates in the laboratory if the limits from primordial big bang nucleosynthesis (BBN) are taken conservatively. In addition, it can be probed by searching for muon number violating processes such as μ → e + γ , and μ →3 e . These rates can well lie within the sensitivities of present experiments. Finally, if we ignore BBN limits we…
Reconstructing Neutrino Properties from Collider Experiments in a Higgs Triplet Neutrino Mass Model
2003
We extend the minimal supersymmetric standard model with bilinear R-parity violation to include a pair of Higgs triplet superfields. The neutral components of the Higgs triplets develop small vacuum expectation values (VEVs) quadratic in the bilinear R-parity breaking parameters. In this scheme the atmospheric neutrino mass scale arises from bilinear R-parity breaking while for reasonable values of parameters the solar neutrino mass scale is generated from the small Higgs triplet VEVs. We calculate neutrino masses and mixing angles in this model and show how the model can be tested at future colliders. The branching ratios of the doubly charged triplet decays are related to the solar neutri…