571 research outputs found
Signatures of supernova neutrino oscillations in the Earth mantle and core
The Earth matter effects on supernova (SN) neutrinos can be identified at a
single detector through peaks in the Fourier transform of their ``inverse
energy'' spectrum. The positions of these peaks are independent of the SN
models and therefore the peaks can be used as a robust signature of the Earth
matter effects, which in turn can distinguish between different neutrino mixing
scenarios. Whereas only one genuine peak is observable when the neutrinos
traverse only the Earth mantle, traversing also the core gives rise to multiple
peaks. We calculate the strengths and positions of these peaks analytically and
explore their features at a large scintillation detector as well as at a
megaton water Cherenkov detector through Monte Carlo simulations. We propose a
simple algorithm to identify the peaks in the actual data and quantify the
chances of a peak identification as a function of the location of the SN in the
sky.Comment: 17 pages, 9 figure
Combining LSND and Atmospheric Anomalies in a Three-Neutrino Picture
We investigate the three-neutrino mixing scheme for solving the atmospheric
and LSND anomalies. We find the region in the parameter space that provides a
good fit to the LSND and the SK atmospheric data, taking into account the CHOOZ
constraint. We demonstrate that the goodness of this fit is comparable to that
of the conventional fit to the solar and atmospheric data. Large values of the
LSND angle are favoured and can be as high as 0.1.
This can have important effects on the atmospheric electron neutrino ratios as
well as on down-going multi-GeV muon neutrino ratios. We examine the
possibility of distinguishing this scheme from the conventional one at the long
baseline experiments. We find that the number of electron neutrino events
observed at the CERN to Gran Sasso experiment may lead us to identify the
scheme, and hence the mass pattern of neutrinos
Neutrino oscillations in low density medium
For the case of small matter effects: , where is the
matter potential, we develop the perturbation theory using as the expansion parameter. We derive simple and physically
transparent formulas for the oscillation probabilities in the lowest order in
which are valid for arbitrary density profile. The formulas can be
applied for propagation of the solar and supernova neutrinos in matter of the
Earth, substantially simplifying numerical calculations. Using these formulas
we study sensitivity of the oscillation effects to structures of the density
profile situated at different distances from the detector . We show that for
the mass-to-flavor state transitions, {\it e.g.}, , the
sensitivity is suppressed for remote structures: ,
where is the oscillation length and is the energy
resolution of detector.Comment: discussion simplified, clarifications adde
Supernova neutrino oscillations: what do we understand?
We summarize our current understanding of the neutrino flavor conversions
inside a core collapse supernova, clarifying the important role played by the
"collective effects" in determining flavor conversion probabilities. The
potentially observable and spectra may help us identify
the neutrino mixing scenario, distinguish between primary flux models, and
learn more about the supernova explosion.Comment: 6 pages, 1 eps figure, jpconf.cls used. Talk given at TAUP 2009,
Rome, July 200
Physics potential of future supernova neutrino observations
We point out possible features of neutrino spectra from a future galactic
core collapse supernova that will enhance our understanding of neutrino mixing
as well as supernova astrophysics. We describe the neutrino flavor conversions
inside the star, emphasizing the role of "collective effects" that has been
appreciated and understood only very recently. These collective effects change
the traditional predictions of flavor conversion substantially, and enable the
identification of neutrino mixing scenarios through signatures like Earth
matter effects.Comment: 8 pages, uses jpconf.cls. Talk given at Neutrino 2008, Christchurch,
NZ. Some entries in Table 2 have been correcte
Weak phase information from the color suppressed B_d^0 -> D^{*0} K^{*0} modes
The decay channels are investigated for extracting
weak phase information. These channels are described by color-suppressed
tree diagrams only and are free from penguin contributions. The branching
ratios for these channels are found to be
which can be measured at the currently running factories. The method
presented here may be well-suited to determine the phase .Comment: 11 pages, revised extensively, version to appear in Phys. Rev.
Observables in the Decays of B to Two Vector Mesons
In general there are nine observables in the decay of a B meson to two vector
mesons defined in terms of polarization correlations of these mesons. Only six
of these can be detected via the subsequent decay angular distributions because
of parity conservation in those decays. The remaining three require the
measurement of the spin polarization of one of the decay products.Comment: 12 pages, no figur
Reducing Penguin Pollution
The most common decay used for measuring 2beta_s, the phase of Bs-Bsbar
mixing, is Bs -> J/psi phi. This decay is dominated by the colour-suppressed
tree diagram, but there are other contributions due to gluonic and electroweak
penguin diagrams. These are often referred to as "penguin pollution" (PP)
because their inclusion in the amplitude leads to a theoretical error in the
extraction of 2beta_s from the data. In the standard model (SM), it is
estimated that the PP is negligible, but there is some uncertainty as to its
exact size. Now, phi_s^{c\bar{c}s} (the measured value of 2beta_s) is small, in
agreement with the SM, but still has significant experimental errors. When
these are reduced, if one hopes to be able to see clear evidence of new physics
(NP), it is crucial to have the theoretical error under control. In this paper,
we show that, using a modification of the angular analysis currently used to
measure phi_s^{c\bar{c}s} in Bs -> J/psi phi, one can reduce the theoretical
error due to PP. Theoretical input is still required, but it is much more
modest than entirely neglecting the PP. If phi_s^{c\bar{c}s} differs from the
SM prediction, this points to NP in the mixing. There is also enough
information to test for NP in the decay. This method can be applied to all
Bs/Bsbar -> V1 V2 decays.Comment: 17 pages, latex, extensive discussion of theoretical error added,
reference added. Further revision: even more detailed discussion of
theoretical error added, as well as an explanation of why the NP strong phase
is negligibl
Discrete ambiguities in extracting weak phases from B decays
Phases of elements of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, as obtained using decays of B mesons to \pi^+ \pi^-, \pi^\pm K^\mp, and \pi^+ K^0 or \pi^- \overline{K}^0, are shown to have a class of discrete ambiguities. In most cases these can be eliminated using other information on CKM phases
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