593 research outputs found
Determining the Neutrino Mass Hierarchy with Atmospheric Neutrinos
The possibility to determine the type of neutrino mass hierarchy by studying
atmospheric neutrino oscillations with a detector capable to distinguish
between neutrino and antineutrino events, such as magnetized iron calorimeters,
is considered. We discuss how the ability to distinguish between the neutrino
mass spectrum with normal and inverted hierarchy depends on detector
characteristics like neutrino energy and direction resolutions or charge
miss-identification, and on the systematical uncertainties related to the
atmospheric neutrino fluxes. We show also how the neutrino mass hierarchy
determination depends on the true values of and , as
well as on the type of the true hierarchy. We find that for -like events,
an accurate reconstruction of the energy and direction of the neutrino greatly
improves the sensitivity to the type of neutrino mass spectrum. For
and a precision of 5% in the reconstruction of
the neutrino energy and in the neutrino direction, the type of
neutrino mass hierarchy can be identified at the 2 C.L. with
approximately 200 events. For resolutions of 15% for the neutrino energy and
for the neutrino direction roughly one order of magnitude larger
event numbers are required. For a detector capable to distinguish between
and induced events the requirements on energy and direction
resolutions are, in general, less demanding than for a detector with muon
charge identification.Comment: 24 pages, 8 figure
4-Neutrino mass schemes and the likelihood of (3+1)-mass spectra
We examine the (3+1)-class of 4-neutrino mass spectra within a rigorous
statistical analysis based on the Bayesian approach to probability. The data of
the Bugey, CDHS and KARMEN experiments are combined by using a likelihood
function. Our statistical approach allows us to incorporate solar and
atmospheric neutrino data and also the result of the CHOOZ experiment via
inequalities which involve elements of the neutrino mixing matrix and are
derived from these data. For any short-baseline we calculate a
bound on the LSND transition amplitude and find that, in the
-- plane, there is no overlap between the 99% CL region
allowed by the latest LSND analysis and the region allowed by our bound on
at 95% CL; there are some small overlap regions if we take the
bound at 99% CL. Therefore, we conclude that, with the existing data, the
(3+1)-neutrino mass spectra are not very likely. However, treating the
(2+2)-spectra with our method, we find that they are well compatible with all
data.Comment: Latex, 22 pages, 3 figure
A 4-neutrino model with a Higgs triplet
We take as a starting point the Gelmini -- Roncadelli model enlarged by a
term with explicit lepton number violation in the Higgs potential and add a
neutrino singlet field coupled via a scalar doublet to the usual leptons. This
scenario allows us to take into account all three present indications in favour
of neutrino oscillations provided by the solar, atmospheric and LSND neutrino
oscillation experiments. Furthermore, it suggests a model which reproduces
naturally one of the two 4-neutrino mass spectra favoured by the data. In this
model the solar neutrino problem is solved by large mixing MSW \nu_e\to\nu_\tau
transitions and the atmospheric neutrino problem by transitions of \nu_\mu into
a sterile neutrino.Comment: Latex, 14 pages, no figure
Cosmic neutrinos at IceCube: , and initial flavor composition
We discuss the prospect of extracting the values of the mixing parameters
and through the detection of cosmic neutrinos in the
planned and forthcoming neutrino telescopes. We take the ratio of the
muon-track to shower-like events, R, as the realistic quantity that can be
measured in the neutrino telescopes. We take into account several sources of
uncertainties that enter the analysis. We then examine to what extent the
deviation of the initial flavor composition from w_e:w_\mu:w_\tau=1:2:0 can be
tested.Comment: 3 pages, 2 figures, Talk given at the TAUP 2009 conference, Rome,
Italy; J. Phys. Conf. Series to appea
How sensitive is a neutrino factory to the angle ?
We consider the impact of non-standard interactions of neutrinos (NSI) on the
determination of neutrino mixing parameters at a neutrino factory using
\pnu{e}\to\pnu{\mu} ``golden channels'' for the measurement of .
We show how a small residual NSI leads to a drastic loss in sensitivity in
, of up to two orders of magnitude. This can be somewhat overcome
if two baselines are combined.Comment: 4 pages, 3 figure
Physics potential of the CERN-MEMPHYS neutrino oscillation project
We consider the physics potential of CERN based neutrino oscillation
experiments consisting of a Beta Beam (BB) and a Super Beam (SPL) sending
neutrinos to MEMPHYS, a 440 kt water \v{C}erenkov detector at Frejus, at a
distance of 130 km from CERN. The discovery reach and the
sensitivity to CP violation are investigated, including a detailed discussion
of parameter degeneracies and systematical errors. For SPL sensitivities
similar to the ones of the phase II of the T2K experiment (T2HK) are obtained,
whereas the BB may reach significantly better sensitivities, depending on the
achieved number of total ion decays. The results for the CERN-MEMPHYS
experiments are less affected by systematical uncertainties than T2HK. We point
out that by a combination of data from BB and SPL a measurement with
antineutrinos is not necessary and hence the same physics results can be
obtained within about half of the measurement time compared to one single
experiment. Furthermore, it is shown how including data from atmospheric
neutrinos in the MEMPHYS detector allows to resolve parameter degeneracies and,
in particular, provides sensitivity to the neutrino mass hierarchy and the
octant of .Comment: 32 pages, 17 figures, minor improvements on the text wrt to v2,
version to appear in JHE
A Supersymmetric Contribution to the Neutrino Mass Matrix and Breaking of mu-tau Symmetry
Supersymmetry broken by anomaly mediation suffers from tachyonic slepton
masses. A possible solution to this problem results in "decoupling", i.e., the
first two generations of sfermions are much heavier than the third one. We note
that in this scenario a sizable loop-induced contribution to the neutrino mass
matrix results. As an application of this scenario we take advantage of the
fact that the decoupling evidently not obeys 2-3 generation exchange symmetry.
In the neutrino sector, this 2-3 symmetry (or mu-tau symmetry) is a useful
Ansatz to generate zero theta_{13} and maximal theta_{23}. The induced
deviations from these values are given for some examples, thereby linking SUSY
breaking to the small parameters (including possibly the solar mass splitting)
of the neutrino sector.Comment: 5 pages, 1 figur
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