Etudes des proprietes des neutrinos dans les contextes ...

tel-00450051, version 1 - 25 Jan 2010
established technology, already successfully applied at relatively large scale
e.g. in Borexino [14, 39] and KamLAND [12] experiments.
3. Liquid Argon.
This detection technology has among the three the best performance in
identifying the topology of interactions and decays of particles, thanks to
the bubble-chamber-like imaging performance. Liquid Argon are very versatile
and work well with a wide particle energy range.
As mentioned above, the availability of future neutrino beams from particle accelerators
would provide a supplementary interest axis to the above experiments.
Measuring oscillations with artificial neutrinos (of well known kinematical features)
with a sufficiently long baseline would allow to accurately determine the
oscillation parameters (in particular the mixing angle θ13 and the CP violating
phase in the mixing matrix). The envisaged detectors may then be used for observing
neutrinos from the future Beta Beams and Super Beams in the optimal
energy range for each experiment.
The measurement of δ
There are mainly three type of experiments able to measure very small θ13 values
and the CP-violating phase: the Beta-Beam, the Super-Beam and the Neutrino
Factory.
The Beta-Beam and the neutrino factory exploit new concepts for the production
of neutrino beams while the superbeams are a well established technology. Beta-
Beams. Zucchelli has first proposed the idea of producing electron (anti)neutrino
beams using the beta-decay of boosted radioactive ions: the ”beta-beam” [115].
It has three main advantages: well-known fluxes, purity (in flavour) and collimation.
In the original scenario, the ions are produced, collected, accelerated up
to several tens GeV/nucleon and stored in a storage ring . The neutrino beam
produced by the decaying ions point to a large water Cerenkov detector about 20
times Super-Kamiokande), located at the (upgraded) Fréjus Underground Laboratory,
130 km away, in order to study CP violation, through a comparison of
νe → νµ and νe → νµ oscillations.
For the two other types, finding δ means to study the CP-violating difference
P(νµ → νe) − P(νµ → νe) between ”neutrino” and ”antineutrino” oscillation
probabilities. To study νµ → νe (νµ → νe) with a super-intense but conventionally
generated neutrino beam, for example, one would create the beam via
the process π + → µ + νi (π − → µ − νi), and detect it via νi + target → e − + ...
(νi + target → e + + ...) Depending on the size of θ13, this CP violation may
be observable with a very intense conventional neutrino beam, or may require a
”neutrino factory” whose neutrinos come from the decay of stored muons.
47