Golden measurements at a neutrino factory

Abstract

The precision and discovery potential of a neutrino factory based on muon storage rings is studied. For three-family neutrino oscillations, we analyse how to measure or severely constraint the angle $\theta_{13}$, CP violation, MSW effects and the sign of the atmospheric mass difference $\Delta m^2_{23}$. We present a simple analytical formula for the oscillation probabilities in matter, with all neutrino mass differences non-vanishing, which clarifies the subtleties involved in disentangling the unknown parameters. The appearance of ``wrong-sign muons'' at three reference baselines is considered: 732 km, 3500 km, and 7332 km. We exploit the dependence of the signal on the neutrino energy, and include as well realistic background estimations and detection efficiencies. The optimal baseline turns out to be ${\cal O}(3000$ km). Analyses combining the information from different baselines are also presented

Interim Design Report

“…For a more detailed discussion of these possible optimisation strategies see reference [100]. The optimisation of the Neutrino Factory has been studied in great detail, for instance, in references [101][102][103][104][105][106][107][108][109][110]. Here we will give a brief summary of the considerations which led to the IDS-NF baseline setup.…”

“…Two possible alternative detector technologies have been considered: either a 20 kTon totally active scintillating detector (TASD) [118] or a 100 kTon liquid argon (LAr) detector [119], both of which would need to be magnetised; a challenging requirement. These detectors would be capable of detecting and identifying the charges of both electrons and muons, providing access to multiple oscillation channels: the ν µ (ν µ ) disappearance channels, as well as the golden (ν e → ν µ andν e →ν µ ) [102] and platinum channels (ν µ → ν e andν µ →ν e ). A detailed description of the assumptions used to simulate the detectors is given in reference [116].…”

“…Oscillations into ν τ , unless suppressed by low efficiency at low energy, enhance both the right-and wrong-sign muon samples. In previous analyses, the poor efficiency of the detector below 10 GeV allowed τ -contamination to be neglected [102,138]. In the case of the detection of the platinum channel, τ -contamination also affects the electron sample.…”

“…The original golden channel at a Neutrino Factory analysis [102] assumed a cylindrical geometry with a cross-sectional radius of 10 m, with iron plates 6 cm thick, scintillator planes 2 cm thick and a 1 T solenoidal field operating at a 50 GeV Neutrino Factory. The International Scoping Study (ISS) [6,305] assumed a cuboidal geometry of 14 × 14 m 2 with 4 cm thick iron and 1 cm thick scintillator and a 1 T dipole field, while operating at a 25 GeV Neutrino Factory.…”

“…The first analysis of the capabilities of a large Magnetised Iron Neutrino Detector to detect the wrong-sign muon signature (the golden channel) was discussed in [102], where it was demonstrated that this combination was capable of extracting the remaining unknown parameters in the threeby-three neutrino mixing matrix. This analysis was carried out assuming a Neutrino Factory with 50 GeV muons, and was optimised for high energy using a detector with 4 cm thick iron plates and 1 cm scintillator planes.…”