Lepton Flavorful Fifth Force and Depth-dependent Neutrino Matter Interactions

TL;DR

This paper explores a proposed fifth force that couples to lepton flavor charges, affecting neutrino interactions and oscillations, with certain parameter spaces still open for experimental probing, especially considering depth-dependent effects underground.

Contribution

It reviews constraints on lepton-flavor-dependent fifth forces and identifies new regions where neutrino oscillation experiments can test these forces, including depth-dependent matter interactions.

Findings

Two parameter regions remain unconstrained by current experiments.

Neutrino oscillation experiments can probe depth-dependent matter effects.

Depth of neutrino beams influences matter interactions relevant for new forces.

Abstract

We consider a fifth force to be an interaction that couples to matter with a strength that grows with the number of atoms. In addition to competing with the strength of gravity a fifth force can give rise to violations of the equivalence principle. Current long range constraints on the strength and range of fifth forces are very impressive. Amongst possible fifth forces are those that couple to lepton flavorful charges $L_e-L_{\mu}$ or $L_e-L_{\tau}$. They have the property that their range and strength are also constrained by neutrino interactions with matter. In this brief note we review the existing constraints on the allowed parameter space in gauged $U(1)_{L_e-L_{\mu}, L_{\tau}}$. We find two regions where neutrino oscillation experiments are at the frontier of probing such a new force. In particular, there is an allowed range of parameter space where neutrino matter interactions relevant for long baseline oscillation experiments depend on the depth of the neutrino beam below the surface of the earth.