90 research outputs found
Earth matter effects on the supernova neutrino spectra
We explore the earth matter effects on the energy spectra of neutrinos from a
supernova. We show that the observations of the energy spectra of and
from a galactic supernova may enable us to identify the solar
neutrino solution, to determine the sign of , and to probe the
mixing matrix element to values as low as . We point out
scenarios in which the matter effects can even be established through the
observation of the spectrum at a single detector.Comment: 8 pages LaTeX, 2 eps figures, uses Rinton-P9x6.cls. Talk given at
CICHEP '2001, Cairo, Egypt, January 200
No-go for exactly degenerate neutrinos at high scale?
We show in a model independent manner that, if the magnitudes of Majorana
masses of neutrinos are exactly equal at some high scale, the radiative
corrections cannot reproduce the observed masses and mixing spectrum at the low
scale, irrespective of the Majorana phases or the mixing angles at the high
scale.Comment: 12 pages ReVTeX, A few typos corrected in the 2nd versio
Resolving ambiguities in the neutrino mass-flavour spectrum from supernova neutrinos
We analyze the neutrino conversions inside a supernova in the 3 mixing
scheme, and their effects on the neutrino spectra observed at the earth. We
find that the observations of the energy spectra of neutrinos from a future
galactic supernova may enable us to identify the solar neutrino solution, to
determine the sign of , and to probe the mixing matrix element
|U_{e3}|^2 to values as low as 10^{-4}-10^{-3}.Comment: 3 pages, 1 eps figure. Talk given at TAUP-99. To be published in
Nucl. Phys. B, Proc. Supp
Quantum mismatch: a powerful measure of "quantumness" in neutrino oscillations
The quantum nature of neutrino oscillations would be reflected in the
mismatch between the neutrino survival probabilities with and without an
intermediate observation. We propose this ``quantum mismatch'' as a measure of
quantumness in neutrino oscillations, which precisely extracts the interference
term in the two-flavor limit. In the full three-flavor scenario, we provide
modified definitions of the Leggett-Garg and quantum mismatch measures. These
are applicable for long-baseline and reactor neutrino experiments that measure
neutrino survival probabilities with negligible matter effects.Comment: 6 pages, 4 figure
How large can the branching ratio of be ?
Motivated by the large like-sign dimuon charge asymmetry observed recently,
whose explanation would require an enhanced decay rate of , we explore how large a branching ratio of this decay mode is allowed
by the present constraints. We use bounds from the lifetimes of and
, constraints from the branching ratios of related
modes, as well as measurements of the mass difference, width difference and
CP-violating phase in the - system. Using an effective field
theory approach, we show that a branching ratio as high as 15% may be allowed
while being consistent with the above constraints. The model with a scalar
leptoquark cannot increase the branching ratio to a per cent level. However, an
enhancement up to 5% is possible in the model with an extremely light with
flavor-dependent interactions, even after all the couplings are taken to be
perturbative. This however cannot account for the dimuon anomaly completely by
itself.Comment: Typos corrected, some discussions added, accepted for publication in
Phys.Rev.
Identifying Earth matter effects on supernova neutrinos at a single detector
The neutrino oscillations in Earth matter introduce modulations in the
supernova neutrino spectra. These modulations can be exploited to identify the
presence of Earth effects on the spectra, which would enable us to put a limit
on the value of the neutrino mixing angle and to identify whether
the mass hierarchy is normal or inverted. We demonstrate how the Earth effects
can be identified at a single detector without prior assumptions about the
flavor-dependent source spectra, using the Fourier transform of the
``inverse-energy'' spectrum of the signal. We explore the factors affecting the
efficiency of this method, and find that the energy resolution of the detector
is the most crucial one. In particular, whereas water Cherenkov detectors may
need a few ten thousand events to identify the Earth effects, a few thousand
may be enough at scintillation detectors, which generically have a much better
energy resolution. A successful identification of the Earth effects through
this method can also provide to a good accuracy. The
relative strength of the detected Earth effects as a function of time provides
a test for supernova models.Comment: 18 pages, 10 figures, JCAP format. Final version to be published in
JCAP. References and some minor clarifications added to the original versio
Radiative magnification of neutrino mixings and a natural explanation of the neutrino anomalies
We show that the neutrino mixing pattern with the large mixing required for
the atmospheric neutrino problem and the small mixing angle MSW solution for
the solar neutrino problem can be naturally generated through radiative
magnification, even though all the mixing angles at the seesaw scale may be
small. This can account for the neutrino anomalies as well as the CHOOZ
constraints in the context of quark-lepton unified theories, where the quark
and lepton mixing angles are expected to be similar in magnitude at the high
scale. We also indicate the 4 mixing scenarios for which this mechanism of
radiative magnification can provide a natural explanation.Comment: 14 pages RevTex, 2 eps figure
Resolving a Discrete Ambiguity in the CKM Angle through and Decays
It is well known that , where is one of the angles of
the unitarity triangle of the CKM matrix, can be determined in a theoretically
clean way by measuring mixing-induced CP violation in the decay . Another clean extraction of this CKM angle is provided by the
time-dependent angular distribution for the decay products of , where we have more observables at
our disposal than in the case of , so that in addition to
also can be probed in a direct way. Unfortunately
a sign ambiguity remains in . If it could be resolved, a discrete
ambiguity in the extraction of the CKM angle could be resolved as well,
which would allow a more incisive test of the CKM model of CP violation. This
note shows that detailed time-dependent studies of and decay processes can determine the sign of
, thereby removing the corresponding ambiguity in the extraction
of the CKM angle .Comment: 5 pages, LaTeX, no figure
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