Neutron Oscillations to Parallel World: Earlier End to the Cosmic Ray Spectrum?

TL;DR

This paper explores how neutron oscillations to a hypothetical mirror neutron could alter the ultrahigh-energy cosmic ray spectrum, potentially affecting the GZK cutoff and neutrino flux, with implications for current and future observatories.

Contribution

It demonstrates that neutron oscillations to a mirror sector can significantly modify cosmic ray spectra and neutrino flux predictions, providing testable signatures for existing and upcoming detectors.

Findings

Shifts the GZK cutoff to lower energies due to baryon non-conservation.

Enhances the spectrum at energies above 100 EeV in the presence of mirror sources.

Predicts a reduction in the diffuse cosmogenic neutrino flux.

Abstract

Present experimental data do not exclude fast oscillation of the neutron $n$ to its degenerate twin from a hypothetical parallel sector, the so called mirror neutron $n'$. We show that this effect brings to a remarkable modifications of the ultrahigh-energy cosmic ray spectrum testable by the present Pierre Auger Observatory (PAO) and Telescope Array (TA) detector, and the future JEM-EUSO experiment. In particular, the baryon non-conservation during UHECR propagation at large cosmological distances shifts the beginning of the GZK cutoff to lower energies, while in presence of mirror sources it may enhance the spectrum at $E \gtrsim 100$ EeV. As a consequence, a significant reduction of the expected diffuse cosmogenic neutrino flux is predicted.