159 research outputs found

### Optimization of the Two-Baseline Beta-Beam

We propose a $\beta$-Beam experiment with four source ions and two baselines
for the best possible sensitivity to $\theta_{13}$, CP violation and mass
hierarchy. Neutrinos from $^{18}$Ne and $^6$He with Lorentz boost $\gamma=350$
are detected in a 500 kton water \chr detector at a distance L=650 km from the
source. Neutrinos from $^8$B and $^8$Li are detected in a 50 kton magnetized
iron detector at a distance L=7000 km from the source. Since a tilt angle
$\vartheta=34.5^\circ$ is required to send the beam to the magic baseline, the
far end of the ring has a maximum depth of $d=2132$ m. We alleviate this
problem by proposing to trade reduction of the decay ring with the increase in
the boost factor of the $^8$Li and $^8$B ions up to
$\gamma_{^8\mathrm{Li}}=390$ and $\gamma_{^8\mathrm{Li}}=650$, such that the
number of events at the detector remains almost the same. We study the
sensitivity reach of this two-baseline two-storage ring $\beta$-Beam
experiment, and compare it with the corresponding reach of the other proposed
facilities.Comment: 5 pages. Based on the talk given at Nufact09, Chicago, July 20-25,
2009. Typos correcte

### Combining dark matter detectors and electron-capture sources to hunt for new physics in the neutrino sector

In this letter we point out the possibility to study new physics in the
neutrino sector using dark matter detectors based on liquid xenon. These are
characterized by very good spatial resolution and extremely low thresholds for
electron recoil energies. When combined with a radioactive $\nu_e$ source, both
features in combination allow for a very competitive sensitivity to neutrino
magnetic moments and sterile neutrino oscillations. We find that, for realistic
values of detector size and source strength, the bound on the neutrino magnetic
moment can be improved by an order of magnitude with respect to the present
value. Regarding sterile neutrino searches, we find that most of the gallium
anomaly could be explored at the 95% confidence level just using shape
information.Comment: 5 pages, 2 figures. Minor modifications, references added. Version
accepted for publication in JHE

### Reassessing the sensitivity to leptonic CP violation

We address the validity of the usual procedure to determine the sensitivity
of neutrino oscillation experiments to CP violation. An explicit calibration of
the test statistic is performed through Monte Carlo simulations for several
experimental setups. We find that significant deviations from a $\chi^2$
distribution with one degree of freedom occur for experimental setups with low
sensitivity to $\delta$. In particular, when the allowed region to which
$\delta$ is constrained at a given confidence level is comparable to the whole
allowed range, the cyclic nature of the variable manifests and the premises of
Wilk's theorem are violated. This leads to values of the test statistic
significantly lower than a $\chi^2$ distribution at that confidence level. On
the other hand, for facilities which can place better constraints on $\delta$
the cyclic nature of the variable is hidden and, as the potential of the
facility improves, the values of the test statistics first become slightly
higher than and then approach asymptotically a $\chi^2$ distribution. The role
of sign degeneracies is also discussed.Comment: 14 pages, 5 figures, RevTeX4. The discussion of the results has been
improved and considerably extended. Version accepted for publication in JHE

### Physics reach of CERN-based SuperBeam neutrino oscillation experiments

We compare the physics potential of two representative options for a
SuperBeam in Europe, studying the achievable precision at 1\sigma with which
the CP violation phase (\delta) could be measured, as well as the mass
hierarchy and CP violation discovery potentials. The first setup corresponds to
a high energy beam aiming from CERN to a 100 kt liquid argon detector placed at
the Pyh\"asalmi mine (2300 km), one of the LAGUNA candidate sites. The second
setup corresponds to a much lower energy beam, aiming from CERN to a 500 kt
water \v{C}erenkov detector placed at the Gran Sasso underground laboratory
(730 km). This second option is also studied for a baseline of 650 km,
corresponding to the LAGUNA candidate sites of Umbria and the Canfranc
underground laboratory. All results are presented also for scenarios with
statistics lowered by factors of 2, 4, 8 and 16 to study the possible
reductions of flux, detector mass or running time allowed by the large value of
\theta_{13} recently measured.Comment: 15 pages, 4 figure

### Quantifying the sensitivity of oscillation experiments to the neutrino mass ordering

Determining the type of the neutrino mass ordering (normal versus inverted)
is one of the most important open questions in neutrino physics. In this paper
we clarify the statistical interpretation of sensitivity calculations for this
measurement. We employ standard frequentist methods of hypothesis testing in
order to precisely define terms like the median sensitivity of an experiment.
We consider a test statistic $T$ which in a certain limit will be normal
distributed. We show that the median sensitivity in this limit is very close to
standard sensitivities based on $\Delta\chi^2$ values from a data set without
statistical fluctuations, such as widely used in the literature. Furthermore,
we perform an explicit Monte Carlo simulation of the INO, JUNO, LBNE, NOvA, and
PINGU experiments in order to verify the validity of the Gaussian limit, and
provide a comparison of the expected sensitivities for those experiments.Comment: 41 pages, 13 figures. Version accepted for publication in JHEP. The
dependence on the atmospheric mixing angle is now explicitly shown also for
long baseline experiments. Minor corrections and references adde

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