Testing Matter Effects in Very Long Baseline Neutrino Oscillation Experiments

TL;DR

This paper evaluates the potential of very long baseline neutrino experiments to test matter effects and measure the mixing angle theta_13, using neutrino factories and analyzing oscillation channels with statistical and flux considerations.

Contribution

It provides a detailed analysis of how very long baseline experiments can detect matter effects and measure theta_13, including flux, event rates, and sensitivity scaling laws.

Findings

Matter effects can be observed for certain theta_13 ranges and baselines.

Long baselines reduce the impact of Delta m^2_{21} effects, aiding CP-violation studies.

Energy spectrum distortions due to MSW effect are potentially measurable.

Abstract

Assuming three-neutrino mixing, we study the capabilities of very long baseline neutrino oscillation experiments to verify and test the MSW effect and to measure the lepton mixing angle theta_13. We suppose that intense neutrino and antineutrino beams will become available in so-called neutrino factories. We find that the most promising and statistically significant results can be obtained by studying nu_e ->nu_mu and \bar{nu}_e-> \bar{nu}_mu oscillations which lead to matter enhancements and suppressions of wrong sign muon rates. We show the theta_13 ranges where matter effects could be observed as a function of the baseline. We discuss the scaling laws of rates, significances and sensitivities with the relevant mixing angles and experimental parameters. Our analysis includes fluxes, event rates and statistical aspects so that the conclusions should be useful for the planning of experimental setups. We discuss the subleading Delta m^2_{21} effects in the case of the LMA MSW solution of the solar problem, showing that they are small for L >= 7000 km. For shorter baselines, Delta m^2_{21} effects can be relevant and their dependence on L offers a further handle for the determination of the CP-violation phase \delta. Finally we comment on the possibility to measure the specific distortion of the energy spectrum due to the MSW effect.