On the energy and baseline optimization to study effects related to the /δphase (CP/Tviolation) in neutrino oscillations at a neutrino factory
Abstract
In this paper we discuss the detection of CP and Tviolation effects in the framework of a neutrino factory. We introduce three quantities, which are good discriminants for a nonvanishing complex phase ( δ) in the 3×3 neutrino mixing matrix: Δ_{δ}, Δ_{CP} and Δ_{T}. We find that these three discriminants (in vacuum) all scale with L/ E_{ν}, where L is the baseline and E_{ν} the neutrino energy. Matter effects modify the scaling, but these effects are large enough to spoil the sensitivity only for baselines larger than 5000 km. So, in the hypothesis of constant neutrino factory power (i.e., number of muons inversely proportional to muon energy), the sensitivity on the δphase is independent of the baseline chosen. Specially interesting is the direct measurement of Tviolation from the "wrongsign" electron channel (i.e., the Δ_{T} discriminant), which involves a comparison of the ν_{e}→ ν_{μ} and ν_{μ}→ ν_{e} oscillation rates. However, the ν_{μ}→ ν_{e} measurement requires magnetic discrimination of the electron charge, experimentally very challenging in a neutrino detector. Since the direction of the electron curvature has to be estimated before the start of the electromagnetic shower, lowenergy neutrino beams and hence short baselines, are preferred. In this paper we show, as an example, the exclusion regions in the Δm^{2}_{12} δ plane using the Δ_{CP} and Δ_{T} discriminants for two concrete cases keeping the same L/ E_{ν} ratio (730 km/7.5 GeV and 2900 km/30 GeV). We obtain a similar excluded region provided that the electron detection efficiency is ∼20% and the charge confusion 0.1%. The Δm^{2}_{12} compatible with the LMA solar data can be tested with a flux of 5×10 ^{21} muons. We compare these results with the fit of the visible energy distributions.
 Publication:

Nuclear Physics B
 Pub Date:
 June 2002
 DOI:
 10.1016/S05503213(02)002110
 arXiv:
 arXiv:hepph/0112297
 Bibcode:
 2002NuPhB.631..239B
 Keywords:

 High Energy Physics  Phenomenology
 EPrint:
 58 pages, 24 figures