117 research outputs found

### A new design for the CERN-Fr\'ejus neutrino Super Beam

We present an optimization of the hadron focusing system for a low-energy
high-intensity conventional neutrino beam (Super-Beam) proposed on the basis of
the HP-SPL at CERN with a beam power of 4 MW and an energy of 4.5 GeV. The far
detector would be a 440 kton Water Cherenkov detector (MEMPHYS) located at a
baseline of 130 km in the Fr\'ejus site. The neutrino fluxes simulation relies
on a new GEANT4 based simulation coupled with an optimization algorithm based
on the maximization of the sensitivity limit on the $\theta_{13}$ mixing angle.
A new configuration adopting a multiple horn system with solid targets is
proposed which improves the sensitivity to $\theta_{13}$ and the CP violating
phase $\delta_{CP}$.Comment: 11 pages, 18 figures, 2 table

### Determination of the neutrino mass hierarchy in the regime of small matter effect

We point out a synergy between T-conjugated oscillation channels in the
determination of the neutrino mass hierarchy with oscillation experiments with
relatively short baselines (L < 700 km), where the matter effect is small. If
information from all four oscillation channels $\nu_\mu\to\nu_e$,
$\bar\nu_\mu\to\bar\nu_e$, $\nu_e\to\nu_\mu$ and $\bar\nu_e\to\bar\nu_\mu$ is
available, a matter effect of few percent suffices to break the sign-degeneracy
and allows to determine the neutrino mass hierarchy. The effect is discussed by
analytical considerations of the relevant oscillation probabilities, and
illustrated with numerical simulations of realistic experimental setups.
Possible configurations where this method could be applied are the combination
of a super beam experiment with a beta beam or a neutrino factory, or a (low
energy) neutrino factory using a detector with muon and electron charge
identification.Comment: 13 pages, 3 figure

### Neutrino oscillations and the effect of the finite lifetime of the neutrino source

We consider a neutrino source at rest and discuss a condition for the
existence of neutrino oscillations which derives from the finite lifetime
$\tau_S$ of the neutrino source particle. This condition is present if the
neutrino source is a free particle such that its wave function is
non-stationary. For a Gaussian wave function and with some simplifying
assumptions, we study the modification of the usual oscillation probability
stemming from $\tau_S$. In the present accelerator experiments the effect of
$\tau_S$ can be neglected. We discuss some experimental situations where the
source lifetime becomes relevant in the oscillation formula.Comment: 13 pages latex file with 2 figure

### Electron neutrino tagging through tertiary lepton detection

We discuss an experimental technique aimed at tagging electron neutrinos in
multi-GeV artificial sources on an event-by-event basis. It exploits in a novel
manner calorimetric and tracking technologies developed in the framework of the
LHC experiments and of rare kaon decay searches. The setup is suited for
slow-extraction, moderate power beams and it is based on an instrumented decay
tunnel equipped with tagging units that intercept secondary and tertiary
leptons from the bulk of undecayed \pi^+ and protons. We show that the taggers
are able to reduce the \nue contamination originating from K_e3 decays by about
one order of magnitude. Only a limited suppression (~60%) is achieved for \nue
produced by the decay-in-flight of muons; for low beam powers, similar
performance as for K_e3 can be reached supplementing the tagging system with an
instrumented beam dump.Comment: 19 pages, 7 figures; minor changes, version to appear in EPJ

### 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

### $\mu-e$ conversion in nuclei within the CMSSM seesaw: universality versus non-universality

In this paper we study $\mu-e$ 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-, $Z$-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, $\tan \beta$, and especially $\theta_{13}$. In the case of
hierachical heavy neutrinos, an extremely high sensitivity of the rates to
$\theta_{13}$ is indeed found. The last part of this work is devoted to the
study of the interesting loss of correlation between the $\mu-e$ conversion and
$\mu \to e \gamma$ rates that occurs in the non-universal scenario. In the case
of large $\tan \beta$ and light $H^0$ Higgs boson an enhanced ratio of the
$\mu-e$ to $\mu \to e \gamma$ 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

### Towards a unique formula for neutrino oscillations in vacuum

We show that all correct results obtained by applying quantum field theory to
neutrino oscillations can be understood in terms of a single oscillation
formula. In particular, the model proposed by Grimus and Stockinger is shown to
be a subcase of the model proposed by Giunti, Kim and Lee, while the new
oscillation formulas proposed by Ioannisian and Pilaftsis and by Shtanov are
disproved. We derive an oscillation formula without making any relativistic
assumption and taking into account the dispersion, so that the result is valid
for both neutrinos and mesons. This unification gives a stronger
phenomenological basis to the neutrino oscillation formula. We also prove that
the coherence length can be increased without bound by more accurate energy
measurements. Finally, we insist on the wave packet interpretation of the
quantum field treatments of oscillations.Comment: 30 pages, 1 figure; the proof that plane wave oscillations do no
exist is extended to stationary models; the influence of dispersion is
explained in more detail

### A Beta Beam complex based on the machine upgrades for the LHC

The Beta Beam CERN design is based on the present LHC injection complex and
its physics reach is mainly limited by the maximum rigidity of the SPS. In
fact, some of the scenarios for the machine upgrades of the LHC, particularly
the construction of a fast cycling 1 TeV injector (``Super-SPS''), are very
synergic with the construction of a higher $\gamma$ Beta Beam. At the energies
that can be reached by this machine, we demonstrate that dense calorimeters can
already be used for the detection of $\nu$ at the far location. Even at
moderate masses (40 kton) as the ones imposed by the use of existing
underground halls at Gran Sasso, the CP reach is very large for any value of
$\theta_{13}$ that would provide evidence of $\nu_e$ appearance at T2K or
NO$\nu$A ($\theta_{13}\geq 3^\circ$). Exploitation of matter effects at the
CERN to Gran Sasso distance provides sensitivity to the neutrino mass hierarchy
in significant areas of the $\theta_{13}-\delta$ plane

### $\theta_{13}$, $\delta$ and the neutrino mass hierarchy at a $\gamma=350$ double baseline Li/B $\beta$-Beam

We consider a $\beta$-Beam facility where $^8$Li and $^8$B ions are
accelerated at $\gamma = 350$, accumulated in a 10 Km storage ring and let
decay, so as to produce intense $\bar \nu_e$ and $\nu_e$ beams. These beams
illuminate two iron detectors located at $L \simeq 2000$ Km and $L \simeq 7000$
Km, respectively. The physics potential of this setup is analysed in full
detail as a function of the flux. We find that, for the highest flux ($10
\times 10^{18}$ ion decays per year per baseline), the sensitivity to
$\theta_{13}$ reaches $\sin^2 2 \theta_{13} \geq 2 \times10^{-4}$; the sign of
the atmospheric mass difference can be identified, regardless of the true
hierarchy, for $\sin^2 2 \theta_{13} \geq 4\times10^{-4}$; and, CP-violation
can be discovered in 70% of the $\delta$-parameter space for $\sin^2 2
\theta_{13} \geq 10^{-3}$, having some sensitivity to CP-violation down to
$\sin^2 2 \theta_{13} \geq 10^{-4}$ for $|\delta| \sim 90^\circ$.Comment: 35 pages, 20 figures. Minor changes, matches the published versio

### The MSW Effect in Quantum Field Theory

We show in detail the general relationship between the Schr\"{o}dinger
equation approach to calculating the MSW effect and the quantum field
theoretical S-matrix approach. We show the precise form a generic neutrino
propagator must have to allow a physically meaningful ``oscillation
probability'' to be decoupled from neutrino production fluxes and detection
cross-sections, and explicitly list the conditions---not realized in cases of
current experimental interest---in which the field theory approach would be
useful.Comment: 20 page REVTeX file, submitted to Phys. Rev.

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