Optimization of the Neutrino Factory, revisited

TL;DR

This paper optimizes the Neutrino Factory's baseline and energy parameters using latest simulations, exploring detector impacts, tau decay effects, and site configurations for different physics goals.

Contribution

It provides updated optimization strategies for the Neutrino Factory, considering recent detector performance and site feasibility, unifying low- and high-energy designs for various parameter spaces.

Findings

Optimal baselines are 2500-5000 km for CP violation.

Muon energies as low as 5 GeV are feasible with new detector analysis.

Multiple global site configurations are viable for the Neutrino Factory.

Abstract

We perform the baseline and energy optimization of the Neutrino Factory including the latest simulation results on the magnetized iron detector (MIND). We also consider the impact of tau decays, generated by nu_mu to nu_tau or nu_e to nu_tau appearance, on the mass hierarchy, CP violation, and theta_{13} discovery reaches, which we find to be negligible for the considered detector. For the baseline-energy optimization for small theta_{13}, we qualitatively recover the results with earlier simulations of the MIND detector. We find optimal baselines of about 2500 km to 5000 km for the CP violation measurement, where now values of E_mu as low as about 12 GeV may be possible. However, for large theta_{13}, we demonstrate that the lower threshold and the backgrounds reconstructed at lower energies allow in fact for muon energies as low as 5 GeV at considerably shorter baselines, such as FNAL-Homestake. This implies that with the latest MIND analysis, low- and high-energy versions of the Neutrino Factory are just two different versions of the same experiment optimized for different parts of the parameter space. Apart from a green-field study of the updated detector performance, we discuss specific implementations for the two-baseline Neutrino Factory, where the considered detector sites are taken to be currently discussed underground laboratories. We find that reasonable setups can be found for the Neutrino Factory source in Asia, Europe, and North America, and that a triangular-shaped storage ring is possible in all cases based on geometrical arguments only.