S. Rigolin

Neutrino mixing and CP-violation

Abstract The prospects of measuring the leptonic angles and CP-odd phases at a neutrino factory are discussed in two scenarios: (1) three active neutrinos as indicated by the present ensemble of atmospheric plus solar data; (2) three active plus one sterile neutrino when the LSND signal is also taken into account. For the latter we develop one and two mass dominance approximations. The appearance of wrong sign muons in long baseline experiments and tau leptons in short baseline ones provides the best tests of CP-violation in scenarios (1) and (2), respectively.

nu(mu) disappearance at the SPL, T2K-I, NO nu A and the neutrino factory

Abstract We study the measurement of the atmospheric neutrino oscillation parameters, θ 23 and Δ m 23 2 , at the ν μ disappearance channel at three conventional beam facilities, the SPL, T2K-phase I and NOνA. These two parameters have been shown to be of crucial importance in the measurement of two of the unknowns of the PMNS mixing matrix, θ 13 and the leptonic CP-violating phase δ. In our analysis, the effect of the two discrete ambiguities, sign ( Δ m 23 2 ) and sign ( tan 2 θ 23 ) , is explicitly taken into account. We analyse also the ν μ disappearance channel at the neutrino factory, and combine it with the “golden” ν e → ν μ and “silver” ν e → ν τ appearance channels to study its impact on the measurement of θ 13 and δ. Eventually, we present the sensitivity of the four facilities to different observables: θ 13 , δ, maximal θ 23 , the sign of the atmospheric mass difference, s atm , and the θ 23 -octant, s oct .

Phenomenology of symmetry breaking from extra dimensions

Motivated by the electroweak hierarchy problem, we consider theories with two extra dimensions in which the four-dimensional scalar fields are components of gauge boson in full space. We explore the Nielsen-Olesen instability for SU(N) on a torus, in the presence of a magnetic background. A field theory approach is developed, computing explicitly the minimum of the complete effective potential, including tri-linear and quartic couplings and determining the symmetries of the stable vacua. We also develop appropriate gauge-fixing terms when both Kaluza-Klein and Landau levels are present and interacting, discussing the interplay between the possible six and four dimensional choices. The equivalence between coordinate dependent and constant Scherk-Schwarz boundary conditions ? associated to either continuous or discrete Wilson lines ? is analyzed.

Four species neutrino oscillations at nu-Factory: sensitivity and CP-violation

The prospects of measuring the leptonic angles and CP-odd phases at a neutrino factory are discussed in the scenario of three active plus one sterile neutrino. We consider the �µ → �e LSND signal. Its associated large mass difference leads to observable neutrino oscillations at short (∼ 1 km) baseline experiments. Sensitivities to the leptonic angles down to 10 −3 can be easily achieved with a 1 Ton detector. Longer baseline experiments (∼ 100 km) with a 1 Kton detector can provide very clean tests of CP-violation especially through tau lepton detection.

νμ disappearance at the SPL, T2K-I and the Neutrino Factory

We study the ν μ disappearance channel at T2K-phase I and the SPL and analyse the achievable reduction of present uncertainties in θ 23 and Δ m 23 2 . We analyse the impact of discrete ambiguities in sign ( Δ m 2 23 ) and sign ( 2 tan θ 23 ) . We show how the disappearance channel at the Neutrino Factory is complementary to the “golden” and “silver” appearance channels and can be used to reduce the eightfold-ambiguity problem in ( θ 13 − δ ) .

Four species neutrino oscillations at ν-Factory: sensitivity and CP-violation

The prospects of measuring the leptonic angles and CP-odd phases at a neutrino factory are discussed in the scenario of three active plus one sterile neutrino. We consider the �µ → �e LSND signal. Its associated large mass difference leads to observable neutrino oscillations at short (∼ 1 km) baseline experiments. Sensitivities to the leptonic angles down to 10 −3 can be easily achieved with a 1 Ton detector. Longer baseline experiments (∼ 100 km) with a 1 Kton detector can provide very clean tests of CP-violation especially through tau lepton detection.

Physics reach of β-beams and ν-factories: the problem of degeneracies

We discuss the physics reach of β -Beams and ν -Factories from a theoretical perspective, having as a guideline the problem of degeneracies. The presence of degenerate solutions in the measure of the neutrino oscillation parameters θ 13 and δ is, in fact, the main problem that have to be addressed in planning future neutrino oscillation experiments. If degeneracies are not (at least partially) solved, it will be almost impossible to perform, at any future facility, precise measurements of θ 13 and/or δ . After a pedagogical introduction on why degenerate solutions arise and how we can get rid of them, we analyze the physics reach of current β -beam and ν -factory configurations. The physics reach of the standard β -Beam is severely affected by degeneracies while a better result can be obtained by higher- γ setups. At the ν -Factory the combination of Golden and Silver channels can solve the eightfold degeneracy down to sin 2 θ 13 ⩽ 10 −3 .

Degeneracies at a β-Beam and a Super-Beam Facility

The presence of degeneracies can considerably worsen the measure of the neutrino oscillation parameters θ 13 and δ. We study the physics reach of a specific “CERN” setup, using a standard β-Beam and Super-Beam facility. These facilities have a similar sensitivity in both parameters. Their combination does not provide any dramatic improvement as expected due to their almost identical L/E ratio. We analyse if adding the correspondent disappearance channels can help in reducing the effect of degeneracies in the ( θ 13 , δ) measure.

Beam and experiments : summary [neutrino studies]

Abstract The discovery of neutrino oscillations marks a major milestone in the history of neutrino physics, and opens a new window to the still mysterious origin of masses and flavour mixing. Many current and forthcoming experiments will answer open questions; however, a major step forward, up to and possibly including CP violation in the neutrino-mixing matrix, requires the neutrino beams from a neutrino factory. The neutrino factory is a new concept for producing neutrino beams of unprecedented quality in terms of intensity, flavour composition, and precision of the beam parameters. Most importantly, the neutrino factory is the only known way to generate a high-intensity beam of electron neutrinos of high energy. The neutrino beam from a neutrino factory, in particular the electron–neutrino beam, enables the exploration of otherwise inaccessible domains in neutrino oscillation physics by exploiting baselines of planetary dimensions. Suitable detectors pose formidable challenges but seem within reach with only moderate extrapolations from existing technologies. Although the main physics attraction of the neutrino factory is in the area of neutrino oscillations, an interesting spectrum of further opportunities ranging from high-precision, high-rate neutrino scattering to physics with high-intensity stopped muons comes with it.