Probing Dark Photon Dark Matter with CTAO

TL;DR

This paper explores how the Cherenkov Telescope Array Observatory can detect or constrain dark photon dark matter by observing spectral features in very-high-energy gamma-ray sources, providing new sensitivity to dark matter models.

Contribution

It introduces a novel method to probe dark photon dark matter using CTAO observations of VHE sources and forecasts sensitivity to kinetic mixing parameters.

Findings

CTAO can probe kinetic mixing down to ~10^{-8}

Spectral attenuation features can reveal dark photon masses around 0.1 eV

Dark matter spikes around black holes affect detection limits

Abstract

The dark photon is a new hypothetical gauge boson arising in extensions of the Standard Model, and constitutes a compelling dark matter candidate. As dark photon dark matter (DPDM), it can interact with electromagnetic fields via kinetic mixing, and the inelastic scattering process $\gamma \gamma' \to e^+ e^-$ becomes kinematically allowed for gamma rays above a characteristic energy threshold. This interaction imprints unique spectral attenuation features at very-high-energies (VHE), offering an observational probe of DPDM models. Using the Cherenkov Telescope Array Observatory (CTAO) Instrument Response Functions (IRFs), we simulate observations of VHE sources and forecast novel sensitivities to the kinetic mixing parameter for the photon-dark photon scattering process. Our study focuses on three key astrophysical targets: the Crab Nebula and the blazars Markarian 421 and Markarian 501. Additionally, we investigate the impact of dark matter spikes around black holes on the upper limits. Our results demonstrate that CTAO can probe the DPDM parameter space down to a mixing parameter of $\varepsilon \sim 10^{-8}$ for masses around $m_{A^{\prime}} \sim 10^{-1}~\textrm{eV}$ through high-energy spectral attenuation, at a $95\%$ confidence level.