1,403 research outputs found
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 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 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 at
3 confidence level for the mass-squared difference in
the range . The latter bound can be improved
by six years of running of the JUNO experiment, , although in the smaller mass range . We have also investigated the impact of sterile
neutrinos on precision measurements of the standard neutrino oscillation
parameters and (at Daya Bay and JUNO),
and (at JUNO), and most importantly, the
neutrino mass hierarchy (at JUNO). We find that, except for the obvious
situation where , 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
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