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

Since decoupling in the early Universe in helicity states, primordial neutrinos propagating in astrophysical magnetic fields precess and undergo helicity changes. In view of various experimental bounds allowing a large magnetic moment of 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 and is a potential 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.

Automated summary

Primordial neutrinos experience helicity flipping in cosmic and galactic magnetic fields, with the flipping probability sensitive to the neutrino magnetic moment and field structure, making it a potential probe for detecting these fields. Even a neutrino magnetic moment lower than that suggested by XENON1T could have a significant impact on relic neutrino helicities and their detection rates.