Nonstandard interaction effects on neutrino parameters at medium-baseline reactor antineutrino experiments

Precision measurements of leptonic mixing parameters and the determination of the neutrino mass hierarchy are the primary goals of the forthcoming medium-baseline reactor antineutrino experiments, such as JUNO and RENO-50. In this work, we investigate the impact of nonstandard neutrino interactions (NSIs) on the measurements of {sin^2 theta_{12}, Delta m^2_{21}} and {sin^2 theta_{13}, Delta m^2_{31}}, and on the sensitivity to the neutrino mass hierarchy, at the medium-baseline reactor experiments by assuming a typical experimental setup. It turns out that the true mixing parameter sin^2 theta_{12} can be excluded at a more than 3 sigma level if the NSI parameter varepsilon_{e mu} or varepsilon_{e tau} is as large as 2% in the most optimistic case. However, the discovery reach of NSI effects has been found to be small, and depends crucially on the CP-violating phases. Finally, we show that NSI effects could enhance or reduce the discrimination power of the JUNO and RENO-50 experiments between the normal and inverted neutrino mass hierarchies.Comment: 18 pages, 7 figures, references updated, matches the published versio

Improved ZZ A Posteriori Error Estimators for Diffusion Problems: Conforming Linear Elements

In \cite{CaZh:09}, we introduced and analyzed an improved Zienkiewicz-Zhu (ZZ) estimator for the conforming linear finite element approximation to elliptic interface problems. The estimator is based on the piecewise "constant" flux recovery in the $H(div;\Omega)$ conforming finite element space. This paper extends the results of \cite{CaZh:09} to diffusion problems with full diffusion tensor and to the flux recovery both in piecewise constant and piecewise linear $H(div)$ space.Comment: arXiv admin note: substantial text overlap with arXiv:1407.437

Effects of nonstandard neutrino interactions at PINGU

Neutrino oscillation experiments in the past decades have greatly improved our knowledge on neutrinos by measuring the fundamental neutrino parameters. The ongoing and upcoming neutrino oscillation experiments are intended to pin down the neutrino mass hierarchy and to discover the leptonic CP violation. By means of neutrino oscillograms, we analyze the impact of non-standard neutrino interactions on neutrino oscillations in the Earth matter. The standard neutrino oscillation probabilities may be significantly changed by non-standard interaction parameters, and in particular, the CP-violating effects in the energy range E = 1 ~ 20 GeV are greatly enhanced. In addition, the event rates of muon neutrinos in the proposed huge atmospheric neutrino experiment, PINGU at the South Pole, have been estimated in the presence of non-standard neutrino interactions. It has been found that the PINGU experiment has very good sensitivities to the non-standard neutrino interaction parameters.Comment: 20 pages, 7 figures, minor changes, matches the published version in Phys. Rev.

Radiative corrections to the leptonic Dirac CP-violating phase

Since the smallest leptonic mixing angle theta_{13} has been measured to be relatively large, it is quite promising to constrain or determine the leptonic Dirac CP-violating phase delta in future neutrino oscillation experiments. Given some typical values of delta = pi/2, pi, and 3pi/2 at the low-energy scale, as well as current experimental results of the other neutrino parameters, we perform a systematic study of the radiative corrections to delta by using the one-loop renormalization group equations in the minimal supersymmetric standard model and the universal extra-dimensional model. It turns out that delta is rather stable against radiative corrections in both models, except for the minimal supersymmetric standard model with a very large value of tan beta. Both cases of Majorana and Dirac neutrinos are discussed. In addition, we use the preliminary indication of delta = (1.08^{+0.28}_{-0.31}) pi or delta = (1.67^{+0.37}_{-0.77}) pi from the latest global-fit analyses of data from neutrino oscillation experiments to illustrate how it will be modified by radiative corrections.Comment: 23 pages, 4 eps figures, minor changes, matches the published versio

Generalized Friedberg-Lee model for neutrino masses and leptonic CP violation from mu-tau symmetry breaking

Assuming the Majorana nature of massive neutrinos, we generalize the Friedberg-Lee neutrino mass model to include CP violation in the neutrino mass matrix M_\nu. The most general case with all the free parameters of M_\nu being complex is discussed. We show that a favorable neutrino mixing pattern (with \theta_12 \approx 35.3^\circ, \theta_23=45^\circ, \theta_13 \neq 0^\circ and \delta=90^\circ) can naturally be derived from M_\nu, if it has an approximate or softly-broken \mu-\tau symmetry. We also point out a different way to obtain the nearly tri-bimaximal neutrino mixing pattern with \delta=0^\circ and non-vanishing Majorana phases.Comment: 4 pages. Talk given by He Zhang at the 4th International Conference on Flavor Physics, 24-28 September 2007, Beijing (to appear in the proceedings

Constraining Sterile Neutrinos Using Reactor Neutrino Experiments

Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experi\-ment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle $\sin^2 2 \theta_{14} \lesssim 0.06$ at 3$\sigma$ confidence level for the mass-squared difference $\Delta m^2_{41}$ in the range $(10^{-3},10^{-1}) \, {\rm eV^2}$. The latter bound can be improved by six years of running of the JUNO experiment, $\sin^22\theta_{14} \lesssim 0.016$, although in the smaller mass range $\Delta m^2_{41} \in (10^{-4} ,10^{-3}) \, {\rm eV}^2$. We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters $\theta_{13}$ and $\Delta m^2_{31}$ (at Daya Bay and JUNO), $\theta_{12}$ and $\Delta m^2_{21}$ (at JUNO), and most importantly, the neutrino mass hierarchy (at JUNO). We find that, except for the obvious situation where $\Delta m^2_{41}\sim \Delta m^2_{31}$, sterile states do not affect these measurements substantially.Comment: 23 pages, 9 figures, more discussions added, matches the published versio

Radiative corrections and explicit perturbations to the tetra-maximal neutrino mixing with large theta_13

The tetra-maximal neutrino mixing pattern predicts a relatively large reactor mixing angle theta_13 \approx 8.4^\circ, which is in good agreement with the latest best-fit value theta_13 = 9^\circ. However, its prediction for theta_12 \approx 30.4^\circ is inconsistent with current oscillation data at the 3sigma C.L. We show that explicit perturbations to the tetra-maximal mixing can naturally enhance theta_12 to its best-fit value theta_12 = 34^\circ. Furthermore, we demonstrate that if the tetra-maximal mixing is produced by a certain flavor symmetry at a high-energy scale Lambda = 10^14 GeV, significant radiative corrections in the minimal supersymmetric standard model can modify theta_12 to be compatible with experimental data at the electroweak scale Lambda_EW = 10^2 GeV. The predictions for theta_13 \approx 8.4^\circ and theta_23 = 45^\circ, as well as the CP-violating phases rho = sigma = -delta = 90^\ciic, are rather stable against radiative corrections.Comment: 14 pages, 3 figures; matches published versio