# The 24th International Spin Symposium

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

## Primordial neutrino helicity modification in magnetic and gravitational fields and implications for their detection

22 Oct 2021, 09:00
20m
Room 403 (Kunibiki Messe)

### Room 403

#### Kunibiki Messe

Parallel Session Presentation Fundamental Symmetries and and Spin Physics Beyond the Standard Model

### Speaker

Jen-Chieh Peng (University of Illinois at Urbana-Champaign)

### Description

The evolution of primordial neutrino helicities in cosmic magnetic fields and gravitational inhomogeneity has been studied recently [1,2]. Detection of relic neutrinos from the Big Bang, e.g., through the inverse tritium beta decay reaction (ITBD) in the PTOLEMY experiment, remains a major challenge. We examine the implications of the helicity properties of the relic neutrinos on their detection in ITBD. While the ITBD rate is insensitive to the helicity of Majorana neutrinos, helicity flips of Dirac neutrinos both via interactions with gravitational perturbations and cosmic and galactic magnetic fields does effect the ITBD detection rate for neutrino masses below $\sim 10^{-2}$ eV. However, resolving relic neutrino events from the tritium beta decay background becomes increasingly difficult with lower neutrino mass, and will require advances in electron detection techniques. We also discuss the prospect for detecting the ITBD reaction for the first time using an intense $^{51}$Cr neutrino source.

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 authors

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