"Secret" neutrino interactions

TL;DR

This work surveys constraints on a hypothetical strong non-standard four-neutrino contact interaction (SNI) using LEP, SN1987A, low-energy meson decays, one-loop Z couplings, and primordial nucleosynthesis. It models SNI as a contact term with coupling $F$, related to a heavy mediator by $F = g_V^2/m_V^2$, and analyzes how different chirality structures (left-handed, right-handed, or mixed) fare under data. The results show that SNI with only left-handed or mixed chiralities cannot exceed the standard weak neutral current strength, while a purely right-handed SNI remains allowed but tightly constrained by multiple scales, including nucleosynthesis. The findings constrain model-building for new neutrino interactions and highlight the importance of multi-scale data, including potential one-loop collider signatures and future high-$q^2$ DIS probes.

Abstract

We review the information about a potentially strong non-standard four-neutrino interaction that can be obtained from available experimental data. By using LEP results and nucleosynthesis data we find that a contact four-fermion neutrino interaction that involve only left-handed neutrinos or both left-handed and right-handed neutrinos cannot be stronger than the standard weak interactions. A much stronger interaction involving only right-handed neutrinos is still allowed.

Figures (2)

• Figure 1: Diagrams contributing to the process $Z\rightarrow \nu\bar{\nu}\nu\bar{\nu}$.
• Figure 2: Diagrams that give contributions to the $Z\bar{\nu} \nu$ vertex in the presence of the non-standard four-neutrino interaction. In diagram (a), neutrinos of different flavours are running in the loop.