Using cosmic neutrinos to search for non-perturbative physics at the Pierre Auger Observatory

TL;DR

This paper explores how the Pierre Auger Observatory can detect signs of new non-perturbative physics through analyzing ultrahigh energy neutrino interactions, potentially revealing physics beyond the Standard Model.

Contribution

It introduces a method to identify non-perturbative physics by comparing neutrino-induced air shower rates, using detailed simulations to determine the required event ratios for discovery.

Findings

Observation of 1 Earth-skimming and 10 quasi-horizontal events can exclude the Standard Model at 99% confidence.

Decade-long observation could detect new physics if neutrino flux and cross-section are favorable.

Detection prospects depend on neutrino flux levels and cross-section enhancements.

Abstract

The Pierre Auger (cosmic ray) Observatory provides a laboratory for studying fundamental physics at energies far beyond those available at colliders. The Observatory is sensitive not only to hadrons and photons, but can in principle detect ultrahigh energy neutrinos in the cosmic radiation. Interestingly, it may be possible to uncover new physics by analyzing characteristics of the neutrino flux at the Earth. By comparing the rate for quasi-horizontal, deeply penetrating air showers triggered by all types of neutrinos, with the rate for slightly upgoing showers generated by Earth-skimming tau neutrinos, we determine the ratio of events which would need to be detected in order to signal the existence of new non-perturbative interactions beyond the TeV-scale in which the final state energy is dominated by the hadronic component. We use detailed Monte Carlo simulations to calculate the effects of interactions in the Earth and in the atmosphere. We find that observation of 1 Earth-skimming and 10 quasi-horizontal events would exclude the standard model at the 99% confidence level. If new non-perturbative physics exists, a decade or so would be required to find it in the most optimistic case of a neutrino flux at the Waxman-Bahcall level and a neutrino-nucleon cross-section an order of magnitude above the standard model prediction.