Hidden Interactions of Sterile Neutrinos As a Probe For New Physics

Recent results from neutrino experiments show evidence for light sterile neutrinos which do not have any Standard Model interactions. In this work we study the hidden interaction of sterile neutrinos with an "MeV scale" gauge boson (the $\nu_s$HI model) with mass $M_X$ and leptonic coupling $g^\prime_l$. By performing an analysis on the $\nu_s$HI model using the data of the MINOS neutrino experiment we find that the values above $G_X/G_F=92.4$ are excluded by more than $2\sigma$ C.L., where $G_F$ is the Fermi constant and $G_X$ is the field strength of the $\nu_s$HI model. Using this model we can also probe other new physics scenarios. We find that the region allowed by the $(g-2)_\mu$ discrepancy is entirely ruled out for $M_X\lesssim 100$ MeV. Finally, the secret interaction of sterile neutrinos has been to solve a conflict between the sterile neutrinos and cosmology. It is shown here that such an interaction is excluded by MINOS for $g^\prime_s> 1.6\times10^{-2}$. This exclusion, however, does depend on the value of $g_l^{\prime}$.Comment: 11 pages, 2 figures, Improved version with new figures and further details. Accepted in PR

Revising Limits on Neutrino-Majoron Couplings

Any theory that have a global spontaneously broken symmetry will imply the existence of very light neutral bosons or massless bosons (sometimes called Majorons). For most of these models we have neutrino-Majoron couplings, that appear as additional branching ratios in decays of mesons and leptons. Here we present an updated limits on the couplings between the electron, muon and tau neutrinos and Majorons. For such we analyze the possible effects of Majoron emission in both meson and lepton decays. In the latter we also include an analysis of the muon decay spectrum. Our results are $|g_{e\alpha}|^{2}<5.5x10^{-6}$, $|g_{\mu\alpha}|^{2}<4.5x10^{-5}$ and $|g_{\tau\alpha}|^{2}<5.5x10^{-2}$ at 90 % C. L., where $\alpha=e,\mu,\tau$.Comment: 12 pages, 5 figure

Atmospheric neutrinos: LMA oscillations, Ue3 induced interference and CP-violation

We consider oscillations of the low energy (sub-GeV sample) atmospheric neutrinos in the three neutrino context. We present the semi-analytic study of the neutrino evolution and calculate characteristics of the e-like events (total number, energy spectra and zenith angle distributions) in the presence of oscillations. At low energies there are three different contributions to the number of events: the LMA contribution (from electron-neutrino oscillations driven by the solar oscillation parameters), the Ue3-contribution proportional to s13**2, and the Ue3 - induced interference of the two amplitudes driven by the solar oscillation parameters. The interference term is sensitive to the CP-violation phase. We describe in details properties of these contributions. We find that the LMA, the interference and Ue3 contributions can reach 5 - 6%, 2 - 3% and 1 - 2 % correspondingly. An existence of the significant (> 3 - 5 %) excess of the e-like events in the sub-GeV sample and the absence of the excess in the multi-GeV range testifies for deviation of the 2-3 mixing from maximum. We consider a possibility to measure the deviation as well as the CP- violation phase in future atmospheric neutrino studies.Comment: 30 pages, RevTeX4.0, 11 figures; improved figure

Constraints on neutrino decay lifetime using long-baseline charged and neutral current data

We investigate the status of a scenario involving oscillations and decay for charged and neutral current data from the MINOS and T2K experiments. We first present an analysis of charged current neutrino and anti-neutrino data from MINOS in the framework of oscillation with decay and obtain a best fit for non-zero decay parameter $\alpha_3$. The MINOS charged and neutral current data analysis results in the best fit for $|\Delta m_{32}^2| = 2.34\times 10^{-3}$~eV$^2$, $\sin^2 \theta_{23} = 0.60$ and zero decay parameter, which corresponds to the limit for standard oscillations. Our combined MINOS and T2K analysis reports a constraint at the 90\% confidence level for the neutrino decay lifetime $\tau_3/m_3 > 2.8 \times 10^{-12}$~s/eV. This is the best limit based only on accelerator produced neutrinos

A Short Travel for Neutrinos in Large Extra Dimensions

Neutrino oscillations successfully explain the flavor transitions observed in neutrinos produced in natural sources like the center of the sun and the earth atmosphere, and also from man-made sources like reactors and accelerators. These oscillations are driven by two mass-squared differences, solar and atmospheric, at the sub-eV scale. However, longstanding anomalies at short-baselines might imply the existence of new oscillation frequencies at the eV-scale and the possibility of this sterile state(s) to mix with the three active neutrinos. One of the many future neutrino programs that are expected to provide a final word on this issue is the Short-Baseline Neutrino Program (SBN) at FERMILAB. In this letter, we consider a specific model of Large Extra Dimensions (LED) which provides interesting signatures of oscillation of extra sterile states. We started re-creating sensitivity analyses for sterile neutrinos in the 3+1 scenario, previously done by the SBN collaboration, by simulating neutrino events in the three SBN detectors from both muon neutrino disappearance and electron neutrino appearance. Then, we implemented neutrino oscillations as predicted in the LED model and also we have performed sensitivity analysis to the LED parameters. Finally, we studied the SBN power of discriminating between the two models, the 3+1 and the LED. We have found that SBN is sensitive to the oscillations predicted in the LED model and have the potential to constrain the LED parameter space better than any other oscillation experiment, for $m_{1}^D<0.1\,\text{eV}$. In case SBN observes a departure from the three active neutrino framework, it also has the power of discriminating between sterile oscillations predicted in the 3+1 framework and the LED ones.Comment: 21 pages, 6 figures, 2 table