Beaming neutrino and antineutrinos across the Earth to disentangle neutrino mixing parameters

TL;DR

This paper proposes using a long-baseline neutrino experiment crossing the Earth to detect tiny CPT violations and tau-antitau appearance, enhancing understanding of neutrino mixing parameters and mass hierarchy.

Contribution

It introduces a novel experimental setup with a CERN or FERMILAB to ICECUBE-Deep Core baseline to detect CPT violation and tau appearance with high sensitivity.

Findings

Potential to detect CPT violation within 6 sigma in one year

Tau-antitau appearance detectable at over 10 sigma annually

Proposes configurations to test theta_13 and neutrino mass hierarchy

Abstract

A MINOS result seemed to hint a different anti-neutrino mass splitting and mixing angle with respect to the neutrino ones, offering a hint for a CPT violation in lepton sector. However more recent MINOS data reduced the neutrino-antineutrino differences leading to a narrow discrepancy almost compatible with no CPT violation, hard to be disentangled. Moreover last a few years of OPERA activity on tau appearance is still un-probed (one unique event). Both flavor muon-tau mixing, tau appearance and eventual CPT violation disentanglement need more tools to be enhanced. Atmospheric muon neutrino spectra and anisotropy in Deep Core at ten-tens GeV (yet unpublished) may test the muon-tau conversion but they can hardly reveal such last tiny MINOS CPT asymmetry. We show how the longest baseline neutrino oscillation available, crossing most of the Earth diameter, within an OPERA-like experiment from CERN (or FERMILAB) to ICECUBE-Deep Core neutrino detector at 21 GeV energy, may at best disentangle even last tiny CPT violation (within 6 sigma a year) while testing at highest rate tau-antitau appearance. We propose the muon neutrino disappearance or (for any CPT violation) the partial anti-muon appearance at the longest distances. Such a tuned detection experiment may lead to a clear and strong signature of tau or anti-tau generation (even within its neutral current noise background events): nearly one antitau or two tau a day. The tau appearance signal is above (or within) 10 sigma a year, even for 1% OPERA-like experiment. Peculiar configurations for theta_13 angle test and hierarchy neutrino mass test may also be addressed by a Deep Core-PINGU array detector observing electron neutrino shower at 6 GeV neutrino energy windows.