200 research outputs found

### Inverted Hierarchy of Neutrino Masses Disfavored by Supernova 1987A

We discuss the flavor conversion of supernova neutrinos in the three-flavor
mixing scheme of neutrinos. We point out that by neutrino observation from
supernova one can discriminate the inverted hierarchy of neutrino masses from
the normal one if s_{13}^2 \gsim a few \times 10^{-4}, irrespective of which
oscillation solution to the solar neutrino problem is realized in nature. We
perform an analysis of data of SN1987A and obtain a strong indication that the
inverted mass hierarchy is disfavored unless s_{13}^2 \lsim a few \times
10^{-4}.Comment: RevTex file, 15 pages, 4 postscript figures, typos corrected, version
to appear in Physics Letters

### On the robustness of IceCube's bound on sterile neutrinos in the presence of non-standard interactions

The mixing parameters of sterile neutrino(s) preferred by the MiniBooNE and
LNSD experiments are in strong tension with the exclusion limit from the
IceCube experiment. Recently it has been claimed that by considering the
non-standard neutrino interactions (NSI) in addition to the sterile neutrino,
the IceCube's limit can be relaxed and the tension can be reconciled; a baroque
scenario as it has been called. We will show that this claim is just an
artifact originating from the energy cuts of the chosen datasets. Contrary to
the claim, by turning on the NSI and fixing the NSI parameters to the proposed
values, not only the IceCube's limit on sterile neutrino cannot be alleviated,
but in fact the tension will be aggravated. The reconciliation, more
appropriately, can be called surreal.Comment: 15 pages, 4 figures; v2: a few clarifications have been adde

### NOvA and T2K: The race for the neutrino mass hierarchy

The determination of the ordering of the neutrino masses (the hierarchy) is
probably a crucial prerequisite to understand the origin of lepton masses and
mixings and to establish their relationship to the analogous properties in the
quark sector. Here, we follow an alternative strategy to the usual
neutrino--antineutrino comparison in long baseline neutrino oscillation
experiments: we exploit the combination of the neutrino-only data from the NOvA
and the T2K experiments by performing these two off-axis experiments at
different distances but at the same $/L$, where $$ is the mean neutrino
energy and $L$ is the baseline. This would require a minor adjustment to the
proposed off-axis angle for one or both of the proposed experiments.Comment: 19 pages, 7 figures, LaTE

### Long Baseline Neutrino Oscillations: Parameter Degeneracies and JHF/NuMI Complementarity

A summary of the parameter degeneracy issue for long baseline neutrino
oscillations is presented and how a sequence of measurements can be used to
resolve all degeneracies. Next, a comparison of the JHF and NuMI Off-Axis
proposals is made with emphasis on how both experiments running neutrinos can
distinguish between the normal and inverted hierarchies provided the E/L of
NuMI is less than or equal to the E/L of JHF. Due to the space limitations of
this proceedings only an executive style summary can be presented here, but the
references and transparencies of the talk contain the detailed arguments.Comment: 6 pages, Latex, 5 postscript figures. Talk presented by Stephen Parke
at NOON 200

### CP and T Violation in Neutrino Oscillations

In this short lecture, we discuss some basic phenomenological aspects of CP
and T violation in neutrino oscillation. Using CP/T trajectory diagrams in the
bi-probability space, we try to sketch out some essential features of the
interplay between the effect of CP/T violating phase and that of the matter in
neutrino oscillation.Comment: 8 pages, 6 figures, Invited talk given by H. Nunokawa at the 10 th
Mexican School of Particles and Fields at Playa del Carmen, Mexico, Oct. 30 -
Nov. 6, 200

### CP and T Trajectory Diagrams for a Unified Graphical Representation of Neutrino Oscillations

Recently the CP trajectory diagram was introduced to demonstrate the
difference between the intrinsic CP violating effects to those induced by
matter for neutrino oscillation. In this paper we introduce the T trajectory
diagram. In these diagrams the probability for a given oscillation process is
plotted versus the probability for the CP- or the T-conjugate processes, which
forms an ellipse as the CP or T violating phase is varied. Since the CP and the
T conjugate processes are related by CPT symmetry, even in the presence of
matter, these two trajectory diagrams are closely related with each other and
form a unified description of neutrino oscillations in matter.Comment: 15 pages, Latex, 7 postscript figure

### On the Mass Eigenstate Purity of B^8 Solar Neutrinos

We give a brief report on our recent paper, hep-ph/0601198, in which we
calculate the nu_2 mass eigenstate purity of B^8 solar neutrinos as 91 +/- 2 %.Comment: 3 pages, 2 postscript figures, latex, AIP conference style. PANIC
2005 proceeding

### Non-unitary evolution of neutrinos in matter and the leptonic unitarity test

We present a comprehensive study of the three-active plus $N$ sterile
neutrino model as a framework for constraining leptonic unitarity violation
induced at energy scales much lower than the electroweak scale. We formulate a
perturbation theory with expansion in small unitarity violating matrix element
$W$ while keeping (non-$W$ suppressed) matter effect to all orders. We show
that under the same condition of sterile state masses $0.1\, \text{eV}^2
\lesssim m^2_{J} \lesssim (1-10)\, \text{GeV}^2$ as in vacuum, assuming typical
accelerator based long-baseline neutrino oscillation experiment, one can derive
a very simple form of the oscillation probability which consists only of
zeroth-order terms with the unique exception of probability leaking term
$\mathcal{C}_{\alpha \beta}$ of $\mathcal{O} (W^4)$. We argue, based on our
explicit computation to fourth-order in $W$, that all the other terms are
negligibly small after taking into account the suppression due to the mass
condition for sterile states, rendering the oscillation probability {\em
sterile-sector model independent}. Then, we identify a limited energy region in
which this suppression is evaded and the effects of order $W^2$ corrections may
be observable. Its detection would provide another way, in addition to
detecting $\mathcal{C}_{\alpha \beta}$, to distinguish between low-scale and
high-scale unitarity violation. We also solve analytically the zeroth-order
system in matter with uniform density to provide a basis for numerical
evaluation of non-unitary neutrino evolution.Comment: 35 content pages + 12 appendix pages, 4 figures; Several clarifying
modifications to match the published versio

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