The neutrino force in neutrino backgrounds: Spin dependence and parity-violating effects

TL;DR

This paper calculates how neutrino backgrounds influence the neutrino force, revealing spin-dependent and parity-violating effects that could impact atomic parity-violation experiments, though currently undetectable.

Contribution

It provides a comprehensive analysis of neutrino forces in various backgrounds, including spin dependence and parity violation, extending previous vacuum-based models.

Findings

Neutrino backgrounds can induce additional parity-violating terms.

The effects are suppressed and below current experimental sensitivity.

Neutrino backgrounds can effectively violate Lorentz invariance.

Abstract

The neutrino force results from the exchange of a pair of neutrinos. A neutrino background can significantly influence this force. In this work, we present a comprehensive calculation of the neutrino force in various neutrino backgrounds with spin dependence taken into account. In particular, we calculate the spin-independent and spin-dependent parity-conserving neutrino forces, in addition to the spin-dependent parity-violating neutrino forces with and without the presence of a neutrino background for both isotropic and anisotropic backgrounds. Compared with the vacuum case, the neutrino background can effectively violate Lorentz invariance and lead to additional parity-violating terms that are not suppressed by the velocity of external particles. We estimate the magnitude of the effect of atomic parity-violation experiments, and it turns out to be well below the current experimental sensitivity.