Evolution of Primordial Neutrino Helicities in Astrophysical Magnetic Fields and Implications for their Detection

TL;DR

This paper investigates how primordial neutrinos' helicities evolve in astrophysical magnetic fields, affecting their detection prospects and potentially serving as probes for cosmic magnetic field structures.

Contribution

It provides the first estimation of relic neutrino helicity flipping probabilities in cosmic and galactic magnetic fields considering neutrino magnetic moments.

Findings

Helicity flipping probability depends on magnetic moment and field structure.

Even small magnetic moments can significantly alter relic neutrino detection rates.

Helicity evolution could serve as a probe for astrophysical magnetic fields.

Abstract

Since decoupling in the early universe in helicity states, primordial neutrinos propagating in astrophysical magnetic fields precess and undergo helicity changes. In view of the XENON1T experiment possibly finding a large magnetic moment of solar neutrinos, we estimate the helicity flipping for relic neutrinos in both cosmic and galactic magnetic fields. The flipping probability is sensitive both to the neutrino magnetic moment and the structure of the magnetic fields, thus potentially a probe of the fields. As we find, even a magnetic moment well below that suggested by XENON1T could significantly affect relic neutrino helicities and their detection rate via inverse tritium beta decay.