80 research outputs found

### Matter Effects on Long Baseline Neutrino Oscillation Experiments

We calculate matter effects on neutrino oscillations relevant for long
baseline neutrino oscillation experiments. In particular, we compare the
results obtained with simplifying approximations for the density profile in the
Earth versus results obtained with actual density profiles. We study the
dependence of the oscillation signals on both $E/\Delta m^2_{atm.}$ and on the
angles in the leptonic mixing matrix. The results show quantitatively how
matter effects can cause significant changes in the oscillation signals,
relative to vacuum oscillations and can be useful in amplifying these signals
and helping one to obtain measurements of mixing parameters and the magnitude
and sign of $\Delta m^2$.Comment: 6 pages, Latex, with 13 postscript figures. Talk given by I. Mocioiu
at the Workshop on the Next Generation Nucleon Decay and Neutrino Detector
NNN99, Stony Brook, Sept. 1999 Journal-ref To appear in the conference
proceedings (A.I.P.), some figures replote

### Limits on the Non-commutativity Scale

A non-vanishing vacuum expectation value for an antisymmetric tensor field
leads to the violation of Lorentz invariance, controlled by the dimension (-2)
parameter, theta_{mu nu}. We assume that the zeroth order term in
theta-expansion represents the Standard Model and study the effects induced by
linear terms in theta_{mu nu}. If coupling to theta_{mu nu} is realized in
strongly interacting sector of the theory, the clock comparison experiments
place the limit on the possible size of this background at the level of
1/\sqrt{theta}>~5X10^{14} GeV. If the interaction with theta_{mu nu} is
initially present only in the QED sector, this limit can be relaxed to
10^{11}-10^{12} GeV level. The strength of these limits obviates the
inferiority of collider physics with regard to experimental checks of Lorentz
invariance. Limits of similar strength are expected to hold in the case of
mixed non-commutativity between four-dimensional and extra-dimensional
coordinates. We also show that in certain models mixed non-commutativity can be
interpreted as 4d CPT-violating background.Comment: 5 pages, Talk presented by Irina Mocioiu at CPT01, Bloomington,
Indiana, August 200

### Oscillation effects on high-energy neutrino fluxes from astrophysical hidden sources

High-energy neutrinos are expected to be produced in a vareity of
astrophysical sources as well as in optically thick hidden sources. We explore
the matter-induced oscillation effects on emitted neutrino fluxes of three
different flavors from the latter class. We use the ratio of electron and tau
induced showers to muon tracks, in upcoming neutrino telescopes, as the
principal observable in our analysis. This ratio depends on the neutrino
energy, density profile of the sources and on the oscillation parameters. The
largely unknown flux normalization drops out of our calculation and only
affects the statistics. For the current knowledge of the oscillation parameters
we find that the matter-induced effects are non-negligible and the enhancement
of the ratio from its vacuum value takes place in an energy range where the
neutrino telescopes are the most sensitive. Quantifying the effect would be
useful to learn about the astrophysics of the sources as well as the
oscillation parameters. If the neutrino telescopes mostly detect diffuse
neutrinos without identifying their sources, then any deviation of the measured
flux ratios from the vacuum expectation values would be most naturally
explained by a large population of hidden sources for which matter-induced
neutrino oscillation effects are important.Comment: Phys.Rev.D accepted version. 12 pages, 10 figures. Results unchanged,
added references, minor changes and text re-arrangement

### Atmospheric neutrino oscillations and tau neutrinos in ice

The main goal of the IceCube Deep Core Array is to search for neutrinos of
astrophysical origins. Atmospheric neutrinos are commonly considered as a
background for these searches. We show here that cascade measurements in the
Ice Cube Deep Core Array can provide strong evidence for tau neutrino
appearance in atmospheric neutrino oscillations. A careful study of these tau
neutrinos is crucial, since they constitute an irreducible background for
astrophysical neutrino detection.Comment: 5 pages, 3 figure

### Non-Standard Neutrino Interactions in the mu-tau sector

We discuss the effects of non-standard neutrino interactions on muon rates in
high statistics atmospheric neutrino oscillation experiments like IceCube
DeepCore. We concentrate on the mu-tau sector, which is presently the least
constrained. It is shown that the magnitude of the effects depends strongly on
the sign of the Epsilon_MuTau parameter describing this non-standard
interactions. A simple analytic model is used to understand the parameter space
where differences between the two signs are maximized. We discuss how this
effect is partially degenerate with changing the neutrino mass hierarchy, as
well as how this degeneracy could be lifted.Comment: 17 pages, 11 figure

### Atmospheric neutrinos in ice and measurement of neutrino oscillation parameters

The main goal of the IceCube Deep Core Array is to search for neutrinos of
astrophysical origins. Atmospheric neutrinos are commonly considered as a
background for these searches. We show that the very high statistics
atmospheric neutrino data can be used to obtain precise measurements of the
main oscillation parameters.Comment: expanded discussion of systematic uncertainties, 8 pages, 4 figure

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