27 research outputs found
Observation of muon neutrino disappearance with the MINOS detectors in the NuMI neutrino beam
This letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rate and energy spectra of charged current muon neutrino interactions are compared in two detectors located along the beam axis at distances of 1 km and 735 km. With 1.27 x 10^{20} 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336 \pm 14.4 events. The data are consistent with muon neutrino disappearance via oscillation with |\Delta m^2_{23}| = 2.74^{+0.44}_{-0.26} x 10^{-3} eV^2/c^4 and sin^2(2\theta_{23}) > 0.87 (at 60% C.L.)
New Results from the MINOS Experiment
In this paper we present the latest results from the MINOS Experiment. This
includes a new measurement of the atmospheric neutrino oscillation parameters
based on 3.36 x 10^20 protons-on-target of data and a first analysis of neutral
current events in the Far Detector. The prospects for nu-e appearance
measurements in MINOS are also discussed.Comment: 6 pages, 4 figures, for the Proceedings of the Neutrino 2008
Conference, Christchurch, N
Global neutrino data and recent reactor fluxes: status of three-flavour oscillation parameters
We present the results of a global neutrino oscillation data analysis within
the three-flavour framework. We include latest results from the MINOS
long-baseline experiment (including electron neutrino appearance as well as
anti-neutrino data), updating all relevant solar (SK II+III), atmospheric (SK
I+II+III) and reactor (KamLAND) data. Furthermore, we include a recent
re-calculation of the anti-neutrino fluxes emitted from nuclear reactors. These
results have important consequences for the analysis of reactor experiments and
in particular for the status of the mixing angle . In our
recommended default analysis we find from the global fit that the hint for
non-zero remains weak, at 1.8 for both neutrino mass
hierarchy schemes. However, we discuss in detail the dependence of these
results on assumptions concerning the reactor neutrino analysis.Comment: 15 pages, 10 figures and 2 tables, v2: corrected version, main
conclusions unchanged, references adde
Neutrino Beams From Electron Capture at High Gamma
We investigate the potential of a flavor pure high gamma electron capture
electron neutrino beam directed towards a large water cherenkov detector with
500 kt fiducial mass. The energy of the neutrinos is reconstructed by the
position measurement within the detector and superb energy resolution
capabilities could be achieved. We estimate the requirements for such a
scenario to be competitive to a neutrino/anti-neutrino running at a neutrino
factory with less accurate energy resolution. Although the requirements turn
out to be extreme, in principle such a scenario could achieve as good abilities
to resolve correlations and degeneracies in the search for sin^2(2 theta_13)
and delta_CP as a standard neutrino factory experiment.Comment: 21 pages, 7 figures, revised version, to appear in JHEP, Fig.7
extended, minnor changes, results unchange
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
Solving the degeneracy of the lepton-flavor mixing angle theta_atm by the T2KK two detector neutrino oscillation experiment
If the atmospheric neutrino oscillation amplitude, sin^2 2theta_atm is not
maximal, there is a two fold ambiguity in the neutrino parameter space: sin^2
theta_atm>0.5 or sin^2 theta_atm<0.5. In this article, we study the impact of
this degeneracy, the so-called octant degeneracy, on the T2KK experiment, which
is a proposed extension of the T2K (Tokai-to-Kaimoka) neutrino oscillation
experiment with an additional water cherenkov detector placed in Korea. We find
that the degeneracy between sin^2 theta_atm= 0.40 and 0.60 can be resolved at
the 3sigma level for sin^2 2theta_rct>0.12 (0.08) for the optimal combination
of a 3.0^circ off-axis beam (OAB) at SK (L=295km) and a 0.5^circ OAB at
L=1000km with a far detector of 100kton volume, after 5 years of exposure with
1.0(5.0) time 10^21 POT/year, if the hierarchy is normal. We also study the
influence of the octant degeneracy on the capability of T2KK experiment to
determine the mass hierarchy and the leptonic CP phase. The capability of
rejecting the wrong mass hierarchy grows with increasing sin^2 theta_atm when
the hierarchy is normal, whereas it is rather insensitive to sin^2 theta_atm
for the inverted hierarchy. We also find that the 1sigma allowed region of the
CP phase is not affected significantly even when the octant degeneracy is not
resolved. All our results are obtained for the 22.5 kton Super-Kamiokande as a
near detector and without an anti-neutrino beam.Comment: 23 pages, 9 figure
conversion in nuclei within the CMSSM seesaw: universality versus non-universality
In this paper we study conversion in nuclei within the context of the
Constrained Minimal Supersymmetric Standard Model, enlarged by three right
handed neutrinos and their supersymmetric partners, and where the neutrino
masses are generated via a seesaw mechanism. Two different scenarios with
either universal or non-universal soft supersymmetry breaking Higgs masses at
the gauge coupling unification scale are considered. In the first part we
present a complete one-loop computation of the conversion rate for this process
that includes the photon-, -boson, and Higgs-boson penguins, as well as box
diagrams, and compare their size in the two considered scenarios. Then, in
these two scenarios we analyse the relevance of the various parameters on the
conversion rates, particularly emphasising the role played by the heavy
neutrino masses, , and especially . In the case of
hierachical heavy neutrinos, an extremely high sensitivity of the rates to
is indeed found. The last part of this work is devoted to the
study of the interesting loss of correlation between the conversion and
rates that occurs in the non-universal scenario. In the case
of large and light Higgs boson an enhanced ratio of the
to rates, with respect to the universal case is
found, and this could be tested with the future experimental sensitivities.Comment: 48 pages, 15 figures. Minor typos corrected and some references adde
Proton driver optimization for new generation neutrino superbeams to search for sub-leading numu->nue oscillations ( angle)
We perform a systematic study of particle production and neutrino yields for
different incident proton energies and baselines , with the aim of
optimizing the parameters of a neutrino beam for the investigation of
-driven neutrino oscillations in the range allowed by
Superkamiokande results. We study the neutrino energy spectra in the
``relevant'' region of the first maximum of the oscillation at a given baseline
. We find that to each baseline corresponds an ``optimal'' proton energy
which minimizes the required integrated proton intensity needed to
observe a fixed number of oscillated events. In addition, we find that the
neutrino event rate in the relevant region scales approximately linearly with
the proton energy. Hence, baselines and proton energies can be
adjusted and the performance for neutrino oscillation searches will remain
approximately unchanged provided that the product of the proton energy times
the number of protons on target remains constant. We apply these ideas to the
specific cases of 2.2, 4.4, 20, 50 and 400 GeV protons. We simulate focusing
systems that are designed to best capture the secondary pions of the
``optimal'' energy. We compute the expected sensitivities to
for the various configurations by assuming the existence
of new generation accelerators able to deliver integrated proton intensities on
target times the proton energy of the order of ${\cal O}(5\times 10^{23})\rm\
GeV\times\rm pot/year$.Comment: 39 pages, 17 figure
The NuMI Neutrino Beam and Potential for an Off-Axis Experiment
The Neutrinos at the Main Injector (NuMI) facility at Fermilab is under
construction and due to begin operations in late 2004. NuMI will deliver an
intense beam of variable energy 2-20 GeV directed into the Earth at
58 mrad. Several aspects of the design are reviewed, and potential limitations
to the ultimate neutrino flux are described. In addition, potential
measurements of neutrino mixing properties are described.Comment: talk given at NuFact '02, Imperial College London, proceedings to
appear in J. Phys. G, revised to add a referenc
Unity of CP and T Violation in Neutrino Oscillations
In a previous work a simultaneous P- CP[P] and P- T[P] bi-probability plot
was proposed as a useful tool for unified graphical description of CP and T
violation in neutrino oscillation. The ``baseball diamond'' structure of the
plot is understood as a consequence of the approximate CP-CP and the T-CP
relations obeyed by the oscillation probabilities. In this paper, we make a
step forward toward deeper understanding of the unified graphical
representation by showing that these two relations are identical in its
content, suggesting a truly unifying view of CP and T violation in neutrino
oscillations. We suspect that the unity reflects the underlying CPT theorem. We
also present calculation of corrections to the CP-CP and the T-CP relations to
leading order in Delta m^2_{21} / Delta m^2_{31} and s^2_{13}.Comment: 20 references added, version to appear in "Focus Issue on Neutrino
Physics" of New Journal of Physic