Semi-contained Interactions of Atmospheric Neutrinos in the MACRO Detector

TL;DR

This study of atmospheric neutrinos in the MACRO detector provides evidence supporting neutrino oscillations, reducing uncertainties and aligning with results from other major experiments like Super-Kamiokande.

Contribution

First detailed analysis of atmospheric neutrino interactions in MACRO that confirms neutrino oscillations and constrains oscillation parameters.

Findings

No-oscillation hypothesis is ruled out.

Results are consistent with neutrino oscillation models.

Combining analyses reduces theoretical uncertainties.

Abstract

Atmospheric neutrinos arise from the decay of particles (primarily pions, muons and kaons) produced in the collision of high energy cosmic ray particles with the atmosphere. The great distances traveled by atmospheric neutrinos between their production and detection make them useful for studying neutrino oscillations, the predicted phenomenon of massive neutrinos changing flavor in flight. This thesis reports a study of atmospheric neutrinos interacting in the MACRO detector. The results, though somewhat clouded by large theoretical uncertainties, clearly rule out the no-oscillations hypothesis, and are consistent with oscillations with the parameters preferred by other MACRO neutrino analyses, as well as those of other experiments (most notably Super-Kamiokande). Combining this analysis with another MACRO neutrino analysis, some of the theoretical errors cancel, further constraining the region of allowed oscillation parameters.