MACRO constraints on violation of Lorentz invariance

TL;DR

This study uses MACRO neutrino data to test for violations of Lorentz invariance, setting stringent limits that support standard neutrino oscillation models and constrain exotic physics.

Contribution

It provides the first stringent experimental limits on Lorentz invariance violation parameters using atmospheric neutrino data, reaffirming the dominance of standard oscillations.

Findings

No evidence of Lorentz invariance violation within the sensitivity of MACRO.

Established upper bounds on the Lorentz violation parameter | v| < 6  10^{-24}.

Limits also constrain potential violations of the Equivalence Principle.

Abstract

The energy spectrum of neutrino-induced upward-going muons in MACRO has been analysed in terms of relativity principles violating effects, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of $\nu_{\mu} \to \nu_{\tau}$ transitions. The data disfavor these exotic possibilities even at a sub-dominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter $|\Delta v| < 6 \times 10^{-24}$ at $\sin 2{\theta}_v$ = 0 and $|\Delta v| < 2.5 \div 5 \times 10^{-26}$ at $\sin 2{\theta}_v$ = $\pm$1. These limits can also be re-interpreted as upper bounds on the parameters describing violation of the Equivalence Principle.