Systematic exploration of the neutrino factory parameter space including errors and correlations

Abstract

We discuss in a systematic way the extraction of neutrino masses, mixing angles and leptonic CP violation at neutrino factories. Compared to previous studies we put a special emphasis on improved statistical methods and on the multidimensional nature of the combined fits of the ν e → ν µ ,ν e →ν µ appearance and ν µ → ν µ ,ν µ →ν µ disappearance channels. Uncertainties of all involved parameters and statistical errors are included. We find previously ignored correlations in the multidimensional parameter space, leading to modifications in the physics reach, which amount in some cases to one order of magnitude. Including proper statistical errors we determine for all parameters the improved sensitivity limits for various baselines, beam energies, neutrino fluxes and detector masses. Our results allow a comparison of the physics potential for different choices of baseline and beam energy with regard to all involved parameters. In addition we discuss in more detail the problem of parameter degeneracies in measurements of δ CP .

Synergies between the first-generation JHF-SK and NuMI superbeam experiments

“…In order to obtain intuitively manageable expressions, one can expand the general oscillation probabilities in powers of the small mass hierarchy parameter α ≡ ∆m 2 21 /∆m 2 31 and the small mixing angle sin 2θ 13 . Though one can also include matter effects in such an approximation, we will, for the sake of simplicity, use here the formulas in vacuum [26,31,61]. Note that the expansion in sin 2θ 13 is always good, since this mixing angle is known to be small.…”

“…The atmospheric ∆m 2 31 -value defines via ∆m 2 31 L/E ν = π/2 the position of the first oscillation maximum L as function of the energy E ν . This leads for typical energies of E ν ∼ 1 − 100 GeV to longbaseline (LBL) experiments, such as the ongoing K2K experiment [9], the MINOS [10] and CNGS [11] experiments just being constructed, and planned "superbeam" [12][13][14][15][16][17][18][19][20][21][22] or "neutrino factory" experiments [23][24][25][26][27][28][29][30][31][32][33][34][35][36]. The solar ∆m 2 21 is, for the favored LMA solution, about two orders of magnitude smaller than the atmospheric ∆m 2 31 , resulting in much longer oscillations lengths for similar energies.…”

Superbeams plus neutrino factory: the golden path to leptonic CP violation

“…Strategies to eliminate some of the fake solutions have previously been discussed, advocating the combination of different baselines [8], an improved experimental technique allowing the measurement of the neutrino energy with good precision [10], the supplementary detection of ν e → ν τ channels [11] and a cluster of detectors at a superbeam facility located at different off-axis angles, so as to have different E [12].…”

“…5 (left), for θ 13 = 8 • and positive sign(∆m 2 13 ). Matter effects are obviously very important in resolving fake sign solutions [19]: the task should thus be easier at large θ 13 and large enough NF baselines, where matter effects are largest 10 . In fact it is easy to prove that no solutions can remain for large enough θ 13 .…”

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.…”