Search results for "Solar neutrino"
showing 10 items of 286 documents
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…
The Not-So-Sterile 4th Neutrino: Constraints on New Gauge Interactions from Neutrino Oscillation Experiments
2014
Sterile neutrino models with new gauge interactions in the sterile sector are phenomenologically interesting since they can lead to novel effects in neutrino oscillation experiments, in cosmology and in dark matter detectors, possibly even explaining some of the observed anomalies in these experiments. Here, we use data from neutrino oscillation experiments, in particular from MiniBooNE, MINOS and solar neutrino experiments, to constrain such models. We focus in particular on the case where the sterile sector gauge boson $A'$ couples also to Standard Model particles (for instance to the baryon number current) and thus induces a large Mikheyev-Smirnov-Wolfenstein potential. For eV-scale ster…
Reconciling dark matter, solar and atmospheric neutrinos
1993
We present models that can reconcile the solar and atmospheric neutrino data with the existence of a hot dark matter component in the universe. This dark matter is a quasi-Dirac neutrino whose mass $m_{DM}$ arises at the one-loop level. The solar neutrino deficit is explained via nonadiabatic conversions of electron neutrino to a sterile neutrino and the atmospheric neutrino data via maximal muon neutrino to tau neutrino oscillations generated by higher order loop diagrams. For $m_{DM} \sim 30$ eV the radiative neutrino decay can lead to photons that can ionize interstellar hydrogen. In one of the models one can have observable $\nu_e$ to $\nu_\tau$ oscillation rates, with no appreciable mu…
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…
Status of the MSW solutions of the solar neutrino problem
2000
We present an updated global analysis of two-flavor MSW solutions to the solar neutrino problem in terms of conversions of nu_e into active or sterile neutrinos. We perform a fit to the full data set corresponding to the 825-day Super-Kamiokande data sample as well as to Chlorine, GALLEX and SAGE experiments. We use all measured total event rates as well as Super-Kamiokande data on the zenith angle dependence, energy spectrum and seasonal variation of the events. For conversions into active neutrinos we find that, although the data on the total event rates favours the Small Mixing Angle (SMA) solution, once the full data set is included both SMA and Large Mixing Angle (LMA) solutions give a…
Light-neutrino mass spectrum, nuclear matrix elements, and the observability of neutrinoless ββ decay
2003
Parameters which describe neutrino flavor oscillations and neutrino mixing mechanisms, obtained from the analysis of the Sudbury Neutrino Observatory (SNO), Super-Kamiokande (SK), CHOOZ, KamLAND and WMAP data, are used to calculate upper limits of the effective neutrino mass 〈mν〉 relevant for the neutrinoless double-beta decay (0νββ). The observability of planned 0νββ experiments, and the present status of the decay of 76Ge are discussed within different light-neutrino mass spectra and by presenting a systematics on the available nuclear matrix elements.
Detection of Atmospheric Muon Neutrinos with the IceCube 9-String Detector
2007
The IceCube neutrino detector is a cubic kilometer TeV to PeV neutrino detector under construction at the geographic South Pole. The dominant population of neutrinos detected in IceCube is due to meson decay in cosmic-ray air showers. These atmospheric neutrinos are relatively well understood and serve as a calibration and verification tool for the new detector. In 2006, the detector was approximately 10% completed, and we report on data acquired from the detector in this configuration. We observe an atmospheric neutrino signal consistent with expectations, demonstrating that the IceCube detector is capable of identifying neutrino events. In the first 137.4 days of live time, 234 neutrino c…
A simple analytic three-flavour description of the day night effect in the solar neutrino flux
2004
In the 3-flavour framework we derive a simple approximate analytic expression for the day-night difference of the flux of solar $\nu_e$ at terrestrial detectors which is valid for an arbitrary Earth density profile. Our formula has the accuracy of a few per cent and reproduces all the known analytic expressions for the Earth matter effects on the solar neutrino oscillations obtained under simplifying assumptions about the Earth's density profile (matter of constant density, 3 layers of constant densities, and adiabatic approximation). It can also be used for studying the Earth matter effects on the oscillations of supernova neutrinos. We also discuss the possibility of probing the leptonic …