2,925 research outputs found
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
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
distribution with one degree of freedom occur for experimental setups with low
sensitivity to . In particular, when the allowed region to which
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 distribution at that confidence level. On
the other hand, for facilities which can place better constraints on
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 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
Searching for sterile neutrinos at the ESSSB
The ESSSB project is a proposed neutrino oscillation experiment based on
the European Spallation Source with the search for leptonic CP as its main aim.
In this letter we show that a near detector at around 1 km distance from the
beamline is not only very desirable for keeping the systematic errors affecting
the CP search under control, but would also provide a significant sensitivity
probe for sterile neutrino oscillations in the region of the parameter space
favored by the long-standing LSND anomaly. We find that the effective mixing
angle can be probed down to at assuming 15% bin-to-bin (un)correlated
systematics.Comment: 8 pages, 1 figur
Freeze-in through portals
The popular freeze-out paradigm for Dark Matter (DM) production, relies on
DM-baryon couplings of the order of the weak interactions. However, different
search strategies for DM have failed to provide a conclusive evidence of such
(non-gravitational) interactions, while greatly reducing the parameter space of
many representative models. This motivates the study of alternative mechanisms
for DM genesis. In the freeze-in framework, the DM is slowly populated from the
thermal bath while never reaching equilibrium. In this work, we analyse in
detail the possibility of producing a frozen-in DM via a mediator particle
which acts as a portal. We give analytical estimates of different freeze-in
regimes and support them with full numerical analyses, taking into account the
proper distribution functions of bath particles. Finally, we constrain the
parameter space of generic models by requiring agreement with DM relic
abundance observations.Comment: 18 pages, 6 figure
Optimization of neutrino oscillation facilities for large \theta_{13}
Up to now, future neutrino beam experiments have been designed and optimized
in order to look for CP violation, \theta_{13} and the mass hierarchy under the
conservative assumption that \theta_{13} is very small. However, the recent
results from T2K and MINOS favor a \theta_{13} which could be as large as
8^{\circ}. In this work, we propose a re-optimization for neutrino beam
experiments in case this hint is confirmed. By switching from the first to the
second oscillation peak, we find that the CP discovery potential of future
oscillation experiments would not only be enhanced, but it would also be less
affected by systematic uncertainties. In order to illustrate the effect, we
present our results for a Super-Beam experiment, comparing the results obtained
at the first and the second oscillation peaks for several values of the
systematic errors. We also study its combination with a \beta-beam facility and
show that the synergy between both experiments would also be enhanced due to
the larger L/E. Moreover, the increased matter effects at the larger L/E also
significantly improves the sensitivity to the mass hierarchy.Comment: Discussion and references expanded. Matches version accepted in JHE
Atmospheric neutrinos in ice and measurement of neutrino oscillation parameters
The main goal of the IceCube Deep Core Array is to search for neutrinos of
astrophysical origins. Atmospheric neutrinos are commonly considered as a
background for these searches. We show that the very high statistics
atmospheric neutrino data can be used to obtain precise measurements of the
main oscillation parameters.Comment: expanded discussion of systematic uncertainties, 8 pages, 4 figure
Non-Unitarity, sterile neutrinos, and Non-Standard neutrino Interactions
The simplest Standard Model extension to explain neutrino masses involves the
addition of right-handed neutrinos. At some level, this extension will impact
neutrino oscillation searches. In this work we explore the differences and
similarities between the case in which these neutrinos are kinematically
accessible (sterile neutrinos) or not (mixing matrix non-unitarity). We clarify
apparent inconsistencies in the present literature when using different
parametrizations to describe these effects and recast both limits in the
popular neutrino non-standard interaction (NSI) formalism. We find that, in the
limit in which sterile oscillations are averaged out at the near detector,
their effects at the far detector coincide with non-unitarity at leading order,
even in presence of a matter potential. We also summarize the present bounds
existing in both limits and compare them with the expected sensitivities of
near future facilities taking the DUNE proposal as a benchmark. We conclude
that non-unitarity effects are too constrained to impact present or near future
neutrino oscillation facilities but that sterile neutrinos can play an
important role at long baseline experiments. The role of the near detector is
also discussed in detail.Comment: 19 pages, 2 figures: minor changes and references added, version
published in JHE
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