86 research outputs found
The neutrino velocity anomaly as an explanation of the missing observation of neutrinos in coincidence with GRB
The search for neutrinos emitted in coincidence with Gamma-Bay Burst has been
so far unsuccessfully. In this paper we show that the recent result reported by
the OPERA Collaboration on an early arrival time of muon neutrinos with respect
to the one computed assuming the speed of light in vacuum could explain the
null search for neutrinos in coincidence with Gamma-Ray Burst
The OPERA experiment
OPERA is a neutrino oscillation experiment designed to perform a nu\_tau
appearance search at long distance in the future CNGS beam from CERN to Gran
Sasso. It is based on the nuclear emulsion technique to distinguish among the
neutrino interaction products the track of a tau produced by a nu\_tau and its
decay tracks. The OPERA detector is presently under construction in the Gran
Sasso underground laboratory, 730 km from CERN, and will receive its first
neutrinos in 2006. The experimental technique is reviewed and the development
of the project described. Foreseen performances in measuring nu\_tau appearance
and also in searching for nu\_e appearance are discussed
Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers
Single gap (gas gap 2 mm) bakelite Resistive Plate Chamber (RPC) modules of
various sizes from 10 cm \times 10 cm to 1 m \times 1 m have been fabricated,
characterized and optimized for efficiency and time resolution. Thin layers of
different grades of silicone compound are applied to the inner electrode
surfaces to make them smooth and also to reduce the surface resistivity. In the
silicone coated RPCs an efficiency > 90% and time resolution \sim 2 ns (FWHM)
have been obtained for both the streamer and the avalanche mode of operation.
Before fabrication of detectors the electrical properties such as bulk
resistivity and surface resistivity of the electrode materials are measured
carefully. Effectiveness of different silicone coating in modifying the surface
resistivity was evaluated by an instrument developed for monitoring the I-V
curve of a high resistive surface. The results indicate definite correlation of
the detector efficiency for the atmospheric muons and the RPC noise rates with
the surface resistivity and its variation with the applied bias voltage. It was
also found that the surface resistivity varies for different grades of silicone
material applied as coating, and the results are found to be consistent with
the detector efficiency and noise rate measurements done with these RPCs.Comment: 9 Pages, 6 figure
Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers
Single gap (gas gap 2 mm) bakelite Resistive Plate Chamber (RPC) modules of
various sizes from 10 cm \times 10 cm to 1 m \times 1 m have been fabricated,
characterized and optimized for efficiency and time resolution. Thin layers of
different grades of silicone compound are applied to the inner electrode
surfaces to make them smooth and also to reduce the surface resistivity. In the
silicone coated RPCs an efficiency > 90% and time resolution \sim 2 ns (FWHM)
have been obtained for both the streamer and the avalanche mode of operation.
Before fabrication of detectors the electrical properties such as bulk
resistivity and surface resistivity of the electrode materials are measured
carefully. Effectiveness of different silicone coating in modifying the surface
resistivity was evaluated by an instrument developed for monitoring the I-V
curve of a high resistive surface. The results indicate definite correlation of
the detector efficiency for the atmospheric muons and the RPC noise rates with
the surface resistivity and its variation with the applied bias voltage. It was
also found that the surface resistivity varies for different grades of silicone
material applied as coating, and the results are found to be consistent with
the detector efficiency and noise rate measurements done with these RPCs.Comment: 9 Pages, 6 figure
A low energy optimization of the CERN-NGS neutrino beam for a theta_{13} driven neutrino oscillation search
The possibility to improve the CERN to Gran Sasso neutrino beam performances
for theta_{13} searches is investigated. We show that by an appropriate
optimization of the target and focusing optics of the present CNGS design, we
can increase the flux of low energy neutrinos by about a factor 5 compared to
the current tau optimized focalisation. With the ICARUS 2.35 kton detector at
LNGS and in case of negative result, this would allow to improve the limit to
sin^22 theta_{13} by an order of magnitude better than the current limit of
CHOOZ at Delta m^2 approximately 3 times 10^{-3} eV^2 within 5 years of nominal
CNGS running. This is by far the most sensitive setup of the currently approved
long-baseline experiments and is competitive with the proposed JHF superbeam.Comment: 19 pages, 8 figure
First hint for CP violation in neutrino oscillations from upcoming superbeam and reactor experiments
We compare the physics potential of the upcoming neutrino oscillation
experiments Daya Bay, Double Chooz, NOvA, RENO, and T2K based on their
anticipated nominal luminosities and schedules. After discussing the
sensitivity to theta_{13} and the leading atmospheric parameters, we
demonstrate that leptonic CP violation will hardly be measurable without
upgrades of the T2K and NOvA proton drivers, even if theta_{13} is large. In
the presence of the proton drivers, the fast track to hints for CP violation
requires communication between the T2K and NOvA collaborations in terms of a
mutual synchronization of their neutrino-antineutrino run plans. Even in that
case, upgrades will only discover CP violation in a relatively small part of
the parameter space at the 3 sigma confidence level, while 90% confidence level
hints will most likely be obtained. Therefore, we conclude that a new facility
will be required if the goal is to obtain a significant result with high
probability.Comment: 27 pages, 12 figure
Comment on superluminality in general relativity
General relativity provides an appropriate framework for addressing the issue
of sub- or superluminality as an apparent effect. Even though a massless
particle travels on the light cone, its average velocity over a finite path
measured by different observers is not necessarily equal to the velocity of
light, as a consequence of the time dilation or contraction in gravitational
fields. This phenomenon occurs in either direction (increase or depletion)
irrespectively of the details and strength of the gravitational interaction.
Hence, it does not intrinsically guarantee superluminality, even when the
gravitational field is reinforced.Comment: 6 page
From parameter space constraints to the precision determination of the leptonic Dirac CP phase
We discuss the precision determination of the leptonic Dirac CP phase
in neutrino oscillation experiments, where we apply the concept
of ``CP coverage''. We demonstrate that this approach carries more information
than a conventional CP violation measurement, since it also describes the
exclusion of parameter regions. This will be very useful for next-generation
long baseline experiments where for sizable first
constraints on can be obtained. As the most sophisticated
experimental setup, we analyze neutrino factories, where we illustrate the
major difficulties in their analysis. In addition, we compare their potential
to the one of superbeam upgrades and next-generation experiments, which also
includes a discussion of synergy effects. We find a strong dependence on the
yet unknown true values of and , as well as
a strong, non-Gaussian dependence on the confidence level. A systematic
understanding of the complicated parameter dependence will be given. In
addition, it is shown that comparisons of experiments and synergy discussions
do in general not allow for an unbiased judgment if they are only performed at
selected points in parameter space. Therefore, we present our results in
dependence of the yet unknown true values of and
. Finally we show that for precision measurements
there exist simple strategies including superbeams, reactor experiments,
superbeam upgrades, and neutrino factories, where the crucial discriminator is
.Comment: 32 pages, 9 figure
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