MACRO results on atmospheric neutrinos

TL;DR

This paper presents the final results of the MACRO experiment on atmospheric neutrino oscillations, providing evidence for nu_mu to nu_tau oscillations with specific parameters, using multiple analysis methods and discussing potential Lorentz invariance violations.

Contribution

It reports the conclusive MACRO data supporting nu_mu to nu_tau oscillations with maximal mixing and details the analysis techniques and uncertainties involved.

Findings

Data favor nu_mu --> nu_tau oscillations with maximal mixing

Energy and angular distributions support oscillation hypothesis

Discussion of potential Lorentz invariance violation effects

Abstract

We discuss the final results of the MACRO experiment on atmospheric neutrino oscillations. The data concern event topologies with average neutrino energies of ~3 and ~50 GeV. Multiple Coulomb Scattering of the high energy muons was used to estimate the neutrino energy event by event. The angular distributions, the L/E_nu distribution, the particle ratios and the absolute fluxes all favor nu_mu --> nu_tau oscillations with maximal mixing and Delta m^2 ~0.0023 eV^2. Emphasis is given to measured ratios which are not affected by Monte Carlo (MC) absolute normalization; a discussion is made on MC uncertainties. A preliminary search for possible Lorentz invariance violation contributions to atmospheric neutrino oscillations is presented and discussed.