nuMSM--Predictions for Neutrinoless Double Beta Decay

We give the prediction on the effective Majorana mass for neutrinoless double $\beta$ decay in a simple extension of the Standard Model (nuMSM). The model adds three right-handed neutrinos with masses smaller than the electroweak scale, and explains dark matter of the Universe. This leads to constraints 1.3meV<m_{bb}^{NH}<3.4meV in normal neutrino mass hierarchy and 13meV<m_{bb}^{IH}<50meV in inverted hierarchy.Comment: 5 page

Sensitivity to neutrino mixing parameters with atmospheric neutrinos

We have analyzed the atmospheric neutrino data to study the octant of $\theta_{23}$ and the precision of the oscillation parameters for a large Iron CALorimeter (ICAL) detector. The ICAL being a tracking detector has the ability to measure the energy and the direction of the muon with high resolution. From bending of the track in magnetic field it can also distinguish its charge. We have generated events by Nuance and then considered only the muons (directly measurable quantities) produced in charge current interactions in our analysis. This encounters the main problem of wide resolutions of energy and baseline. The energy-angle correlated two dimensional resolution functions are used to migrate the energy and the zenith angle of the neutrino to those of the muon. A new type of binning has been introduced to get better reflection of the oscillation pattern in chi-square analysis. Then the marginalization of the $\chi^2$ over all parameters has been carried out for neutrinos and anti-neutrinos separately. We find that the measurement of $\theta_{13}$ is possible at a significant precision with atmospheric neutrinos. The precisions of $\Delta m_{32}^2$ and $\sin^2\theta_{23}$ are found $\sim$ 8% and 38%, respectively, at 90% CL. The discrimination of the octant as well as the deviation from maximal mixing of atmospheric neutrinos are also possible for some combinations of ($\theta_{23}, ~\theta_{13}$). We also discuss the impact of the events at near horizon on the precision studies.Comment: 16 pages, 12 figures, new results added; accepted for publication in Phys. Rev.

The diffuse neutrino flux from supernovae: upper limit on the electron neutrino component from the non-observation of antineutrinos at SuperKamiokande

I derive an upper bound on the electron neutrino component of the diffuse supernova neutrino flux from the constraint on the antineutrino component at SuperKamiokande. The connection between antineutrino and neutrino channels is due to the similarity of the muon and tau neutrino and antineutrino fluxes produced in a supernova, and to the conversion of these species into electron neutrinos and antineutrinos inside the star. The limit on the electron neutrino flux is 5.5 cm^-2 s^-1 above 19.3 MeV of neutrino energy, and is stronger than the direct limit from Mont Blanc by three orders of magnitude. It represents the minimal sensitivity required at future direct searches, and is intriguingly close to the reach of the Sudbury Neutrino Observatory (SNO) and of the ICARUS experiment. The electron neutrino flux will have a lower bound if the electron antineutrino flux is measured. Indicatively, the first can be smaller than the second at most by a factor of 2-3 depending on the details of the neutrino spectra at production.Comment: LaTeX, 5 pages, 1 figure. Paper is modified in the presentation (Fig. 1 was replaced with a different plot and Table 1 was expanded), with unchanged results. References added and correcte

Flavor stability analysis of dense supernova neutrinos with flavor-dependent angular distributions

Numerical simulations of the supernova (SN) neutrino self-induced flavor conversions, associated with the neutrino-neutrino interactions in the deepest stellar regions, have been typically carried out assuming the "bulb-model". In this approximation, neutrinos are taken to be emitted half-isotropically by a common neutrinosphere. In the recent Ref. \cite{Mirizzi:2011tu} we have removed this assumption by introducing flavor-dependent angular distributions for SN neutrinos, as suggested by core-collapse simulations. We have found that in this case a novel multi-angle instability in the self-induced flavor transitions can arise. In this work we perform an extensive study of this effect, carrying out a linearized flavor stability analysis for different SN neutrino energy fluxes and angular distributions, in both normal and inverted neutrino mass hierarchy. We confirm that spectra of different nu species which cross in angular space (where F_{\nu_e}=F_{\nu_x} and F_{\bar\nu_e}=F_{\bar\nu_x}) present a significant enhancement of the flavor instability, and a shift of the onset of the flavor conversions at smaller radii with respect to the case of an isotropic neutrino emission. We also illustrate how a qualitative (and sometimes quantitative) understanding of the dynamics of these systems follows from a stability analysis.Comment: (v2: revised version. 10 pages, 10 eps figures. References updated. Figures imrproved. Matches the version published in PRD.

On detecting CP violation in a single neutrino oscillation channel at very long baselines

We propose a way of detecting CP violation in a single neutrino oscillation channel at very long baselines (on the order of several thousands of kilometers), given precise knowledge of the smallest mass-squared difference. It is shown that CP violation can be characterized by a shift in $L/E$ of the peak oscillation in the $\nu_e$--$\nu_\mu$ appearance channel, both in vacuum and in matter. In fact, matter effects enhance the shift at a fixed energy. We consider the case in which sub-GeV neutrinos are measured with varying baseline and also the case of a fixed baseline. For the varied baseline, accurate knowledge of the absolute neutrino flux would not be necessary; however, neutrinos must be distinguishable from antineutrinos. For the fixed baseline, it is shown that CP violation can be distinguished if the mixing angle $\theta_{13}$ were known.Comment: 8 pages, 9 figures; minor typos correcte

A test of tau neutrino interactions with atmospheric neutrinos and K2K

The presence of a tau component in the flux of atmospheric neutrinos inside the Earth, due to flavor oscillations, makes these neutrinos a valuable probe of interactions of the tau neutrino with matter. We study -- analytically and numerically -- the effects of nonstandard interactions in the nu_e-nu_tau sector on atmospheric neutrino oscillations, and calculate the bounds on the exotic couplings that follow from combining the atmospheric neutrino and K2K data. We find very good agreement between numerical results and analytical predictions derived from the underlying oscillation physics. While improving on existing accelerator bounds, our bounds still allow couplings of the size comparable to the standard weak interaction. The inclusion of new interactions expands the allowed region of the vacuum oscillation parameters towards smaller mixing angles, 0.2 ~< sin^2 theta_{23} ~< 0.7, and slightly larger mass squared splitting, 1.5 * 10^{-3} eV^2 ~< |\Delta m^2_{23}| ~< 4.0 * 10^{-3} eV^2, compared to the standard case. The impact of the K2K data on all these results is significant; further important tests of the nu_e-nu_tau exotic couplings will come from neutrino beams experiments such as MINOS and long baseline projects.Comment: 8 figures, some typos corrected, minor editing in the reference

Stability analysis of collective neutrino oscillations in the supernova accretion phase with realistic energy and angle distributions

We revisit our previous results on the matter suppression of self-induced neutrino flavor conversions during a supernova (SN) accretion phase, performing a linearized stability analysis of the neutrino equations of motion, in the presence of realistic SN density profiles. In our previous numerical study, we used a simplified model based on an isotropic neutrino emission with a single typical energy. Here, we take into account realistic neutrino energy and angle distributions. We find that multi-energy effects have a sub-leading impact in the flavor stability of the SN neutrino fluxes with respect to our previous single-energy results. Conversely, realistic forward-peaked neutrino angular distributions would enhance the matter suppression of the self-induced oscillations with respect to an isotropic neutrino emission. As a result, in our models for iron-core SNe, collective flavor conversions have a negligible impact on the characterization of the observable neutrino signal during the accretion phase. Instead, for a low-mass O-Ne-Mg core SN model, with lower matter density profile and less forward-peaked angular distributions, collective conversions are possible also at early times.Comment: v2: 8 pages, 3 eps figures. Revised version. Minor changes. References updated. Matches the version published on PR

What Fraction of Boron-8 Solar Neutrinos arrive at the Earth as a nu_2 mass eigenstate?

We calculate the fraction of B^8 solar neutrinos that arrive at the Earth as a nu_2 mass eigenstate as a function of the neutrino energy. Weighting this fraction with the B^8 neutrino energy spectrum and the energy dependence of the cross section for the charged current interaction on deuteron with a threshold on the kinetic energy of the recoil electrons of 5.5 MeV, we find that the integrated weighted fraction of nu_2's to be 91 \pm 2 % at the 95% CL. This energy weighting procedure corresponds to the charged current response of the Sudbury Neutrino Observatory (SNO). We have used SNO's current best fit values for the solar mass squared difference and the mixing angle, obtained by combining the data from all solar neutrino experiments and the reactor data from KamLAND. The uncertainty on the nu_2 fraction comes primarily from the uncertainty on the solar delta m^2 rather than from the uncertainty on the solar mixing angle or the Standard Solar Model. Similar results for the Super-Kamiokande experiment are also given. We extend this analysis to three neutrinos and discuss how to extract the modulus of the Maki-Nakagawa-Sakata mixing matrix element U_{e2} as well as place a lower bound on the electron number density in the solar B^8 neutrino production region.Comment: 23 pages, 8 postscript figures, latex. Dedicated to the memory of John Bahcall who championed solar neutrinos for many lonely year