29 research outputs found
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
MiniBooNE and LSND data: non-standard neutrino interactions in a (3+1) scheme versus (3+2) oscillations
The recently observed event excess in MiniBooNE anti-neutrino data is in
agreement with the LSND evidence for electron anti-neutrino appearance. We
propose an explanation of these data in terms of a (3+1) scheme with a sterile
neutrino including non-standard neutrino interactions (NSI) at neutrino
production and detection. The interference between oscillations and NSI
provides a source for CP violation which we use to reconcile different results
from neutrino and anti-neutrino data. Our best fit results imply NSI at the
level of a few percent relative to the standard weak interaction, in agreement
with current bounds. We compare the quality of the NSI fit to the one obtained
within the (3+1) and (3+2) pure oscillation frameworks. We also briefly comment
on using NSI (in an effective two-flavour framework) to address a possible
difference in neutrino and anti-neutrino results from the MINOS experiment.Comment: 28 pages, 9 figures, discussion improved, new appendix added,
conclusions unchange
Learning from tau appearance
The study of numu->nutau oscillation and the explicit observation of the
nutau through the identification of the final-state tau lepton ("direct
appearance search") represent the most straightforward test of the oscillation
phenomenon. It is, nonetheless, the most challenging from the experimental
point of view. In this paper we discuss the current empirical evidence for
direct appearance of tau neutrinos at the atmospheric scale and the
perspectives for the next few years, up to the completion of the CNGS physics
programme. We investigate the relevance of this specific oscillation channel to
gain insight into neutrino physics within the standard three-family framework.
Finally, we discuss the opportunities offered by precision studies of
numu->nutau transitions in the occurrence of more exotic scenarios emerging
from additional sterile neutrinos or non-standard interactions.Comment: 26 pages, 7 figures, to appear in NJ
The minimal 3+2 neutrino model versus oscillation anomalies
We study the constraints imposed by neutrino oscillation experiments on the minimal extension of the Standard Model that can explain neutrino masses, which requires the addition of just two singlet Weyl fermions. The most general renormalizable couplings of this model imply generically four massive neutrino mass eigenstates while one remains massless: it is therefore a minimal 3+2 model. The possibility to account for the confirmed solar, atmospheric and long-baseline oscillations, together with the LSND/MiniBooNE and reactor anomalies is addressed. We find that the minimal model can fit oscillation data including the anomalies better than the standard 3ν model and similarly to the 3+2 phenomenological models, even though the number of free parameters is much smaller than in the latter. Accounting for the anomalies in the minimal model favours a normal hierarchy of the light states and requires a large reactor angle, in agreement with recent measurements. Our analysis of the model employs a new parametrization of seesaw models that extends the Casas-Ibarra one to regimes where higher order corrections in the light-heavy mixings are significant
Theta_13: phenomenology, present status and prospect
The leptonic mixing angle theta_13 is currently a high-priority topic in the
field of neutrino physics, with five experiments under way, searching for
neutrino oscillations induced by this angle. We review the phenomenology of
theta_13 and discuss the information from present global oscillation data. A
description of the upcoming reactor and accelerator experiments searching for a
non-zero value of theta_13 is given, and we evaluate the sensitivity reach
within the next few years.Comment: Topical review, 55 pages, 23 figures, v2: various minor improvements,
references added, new section 6, matches version to appear in J. Phys.
High intensity neutrino oscillation facilities in Europe
The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Fréjus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of μ+ and μ− beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular He6 and Ne18, also stored in a ring. The far detector is also the MEMPHYS detector in the Fréjus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the physics reach of each facility, in particular for the measurement of CP violation in the lepton sector, and estimated the cost of construction. These have demonstrated that the best facility to build is the Neutrino Factory. However, if a powerful proton driver is constructed for another purpose or if the MEMPHYS detector is built for astroparticle physics, the Super Beam also becomes very attractive
Interim Design Report
The International Design Study for the Neutrino Factory (the IDS-NF) was
established by the community at the ninth "International Workshop on Neutrino
Factories, super-beams, and beta- beams" which was held in Okayama in August
2007. The IDS-NF mandate is to deliver the Reference Design Report (RDR) for
the facility on the timescale of 2012/13. In addition, the mandate for the
study [3] requires an Interim Design Report to be delivered midway through the
project as a step on the way to the RDR. This document, the IDR, has two
functions: it marks the point in the IDS-NF at which the emphasis turns to the
engineering studies required to deliver the RDR and it documents baseline
concepts for the accelerator complex, the neutrino detectors, and the
instrumentation systems. The IDS-NF is, in essence, a site-independent study.
Example sites, CERN, FNAL, and RAL, have been identified to allow site-specific
issues to be addressed in the cost analysis that will be presented in the RDR.
The choice of example sites should not be interpreted as implying a preferred
choice of site for the facility
Testing Nonstandard Neutrino Properties with a M\"ossbauer Oscillation Experiment
If the neutrino analogue of the M\"ossbauer effect, namely, recoiless
emission and resonant capture of neutrinos is realized, one can study neutrino
oscillations with much shorter baselines and smaller source/detector size when
compared to conventional experiments. In this work, we discuss the potential of
such a M\"ossbauer neutrino oscillation experiment to probe nonstandard
neutrino properties coming from some new physics beyond the standard model. We
investigate four scenarios for such new physics that modify the standard
oscillation pattern. We consider the existence of a light sterile neutrino that
can mix with \bar \nu_e, the existence of a Kaluza-Klein tower of sterile
neutrinos that can mix with the flavor neutrinos in a model with large flat
extra dimensions, neutrino oscillations with nonstandard quantum decoherence
and mass varying neutrinos, and discuss to which extent one can constrain these
scenarios. We also discuss the impact of such new physics on the determination
of the standard oscillation parameters.Comment: 28 pages, 11 figures, published version in JHE
Non-Standard Neutrino Interactions at One Loop
Neutrino oscillation experiments are known to be sensitive to Non-Standard
Interactions (NSIs). We extend the NSI formalism to include one-loop effects.
We discuss universal effects induced by corrections to the tree level W
exchange, as well as non-universal effects that can arise from scalar charged
current interactions. We show how the parameters that can be extracted from the
experiments are obtained from various loop amplitudes, which include vertex
corrections, wave function renormalizations, mass corrections as well as box
diagrams. As an illustrative example, we discuss NSIs at one loop in the
Minimal Supersymmetric Standard Model (MSSM) with generic lepton flavor
violating sources in the soft sector. We argue that the size of one-loop NSIs
can be large enough to be probed in future neutrino oscillation experiments.Comment: 27 pages, 4 figure