Neutrino factory in stages: Low energy, high energy, off-axis

TL;DR

This paper explores staged neutrino factory designs, optimizing for different theta_13 values, and considers upgrades like energy, baselines, and off-axis detectors to enhance physics reach.

Contribution

It proposes a flexible, staged approach to neutrino factory development, including off-axis detectors and re-optimization based on theta_13 measurements, for comprehensive physics exploration.

Findings

Low energy neutrino factory suitable for large theta_13

High energy upgrade beneficial for new physics searches

Off-axis detectors enhance experimental versatility

Abstract

We discuss neutrino oscillation physics with a neutrino factory in stages, including the possibility of upgrading the muon energy within the same program. We point out that a detector designed for the low energy neutrino factory may be used off-axis in a high energy neutrino factory beam. We include the re-optimization of the experiment depending on the value of theta_13 found. As upgrade options, we consider muon energy, additional baselines, a detector mass upgrade, an off-axis detector, and the platinum (muon to electron neutrino) channels. In addition, we test the impact of Daya Bay data on the optimization. We find that for large theta_13 (theta_13 discovered by the next generation of experiments), a low energy neutrino factory might be the most plausible minimal version to test the unknown parameters. However, if a higher muon energy is needed for new physics searches, a high energy version including an off-axis detector may be an interesting alternative. For small theta_13 (theta_13 not discovered by the next generation), a plausible program could start with a low energy neutrino factory, followed by energy upgrade, and then baseline or detector mass upgrade, depending on the outcome of the earlier phases.