Dark Photons from the Center of the Earth: Smoking-Gun Signals of Dark Matter

TL;DR

This paper proposes that dark matter accumulated in Earth's core could annihilate into dark photons, producing detectable signals like muon tracks, which could be observed by neutrino and cosmic ray detectors, providing a new way to identify dark matter.

Contribution

It introduces a novel detection method for dark matter via dark photon signals from Earth's center, including detailed rate calculations and potential observable signatures.

Findings

Dark matter can produce detectable signals through dark photon decay.

Large, distinctive signals like parallel muon tracks are possible.

Some parameter regions are accessible to current neutrino and cosmic ray detectors.

Abstract

Dark matter may be charged under dark electromagnetism with a dark photon that kinetically mixes with the Standard Model photon. In this framework, dark matter will collect at the center of the Earth and annihilate into dark photons, which may reach the surface of the Earth and decay into observable particles. We determine the resulting signal rates, including Sommerfeld enhancements, which play an important role in bringing the Earth's dark matter population to their maximal, equilibrium value. For dark matter masses $m_X \sim$ 100 GeV - 10 TeV, dark photon masses $m_{A'} \sim$ MeV - GeV, and kinetic mixing parameters $\varepsilon \sim 10^{-10} - 10^{-8}$, the resulting electrons, muons, photons, and hadrons that point back to the center of the Earth are a smoking-gun signal of dark matter that may be detected by a variety of experiments, including neutrino telescopes, such as IceCube, and space-based cosmic ray detectors, such as Fermi-LAT and AMS. We determine the signal rates and characteristics, and show that large and striking signals---such as parallel muon tracks---are possible in regions of the $(m_{A'}, \varepsilon)$ plane that are not probed by direct detection, accelerator experiments, or astrophysical observations.