18-22 October 2021
Matsue, Shimane Prefecture, Japan
Asia/Tokyo timezone

Evolution of primordial neutrino helicities in cosmic magnetic fields and gravitational inhomogeneities

22 Oct 2021, 08:40
Room 403 (Kunibiki Messe)

Room 403

Kunibiki Messe

Parallel Session Presentation Fundamental Symmetries and and Spin Physics Beyond the Standard Model Joint BSM - Lowenergy - Future Session US timezone


Gordon Baym (University of Illinois) Prof. Jen-Chieh Peng (University of Illinois)


Primordial neutrinos decoupled in the early universe predominantly in helicity eigenstates. Their subsequent propagation through the residual cosmic and galactic magnetic fields partially flips their helicities.[1] In view of the possibility of large neutrino magnetic moments arising from beyond-the-standard-model physics -- e.g., as the XENON1T experiment reported as a possible explanation of their low energy event excess -- we estimate the magnitudes of the helicity flips for relic Dirac neutrinos both in galactic and cosmic magnetic fields. Majorana neutrinos would not undergo such flips. The helicity flip probability is sensitive not only to the magnetic moment of neutrinos but also to the properties of galactic and cosmic fields, and thus can thus potentially probe astrophysical magnetic fields. We find that even a moment several orders of magnitude smaller than that possibly found by XENON1T could lead to significant helicity changes of Dirac neutrinos as they propagate to detectors on Earth. We also discuss the effects of gravitational inhomogeneities on the helicity of primordial neutrinos.[2]

[1] G. Baym and J. C. Peng, Phys. Rev. Lett. 126, 191803 (2021).
[2] G. Baym and J. C. Peng, Phys. Rev. D 103, 123019 (2021).

Primary author

Gordon Baym (University of Illinois)


Prof. Jen-Chieh Peng (University of Illinois)

Presentation Materials