# Wobbly Dark Matter Signals at Cherenkov Telescopes from Long Lived Mediator Decays

## TL;DR

This paper explores how long-lived mediators in dark matter annihilation can affect Cherenkov telescope observations, creating unique spectral features and background contamination that can be used to identify dark matter signals.

## Contribution

It introduces the impact of long-lived mediators on IACT dark matter searches, highlighting new spectral features and background challenges that can aid in signal identification.

## Key findings

- Gamma-ray spectrum changes with observation angle.
- Hard excess at high energies in the spectrum.
- Background contamination affects signal reconstruction.

## Abstract

Imaging Atmospheric Cherenkov Telescope (IACT) searches for dark matter often perform observations in "wobble mode", i.e. collecting data from the signal region and from a corresponding background control region at the same time, enabling efficient simultaneous determination and subtraction of background. This observation strategy is possibly compromised in scenarios where dark matter annihilates to long-lived mediators that can traverse astrophysical distances before decaying to produce the gamma rays observed by the IACTs. In this paper, we show that this challenge comes with several interesting features and opportunities: in addition to signal contamination in the background control region, the gamma-ray spectrum changes with the observing direction angle and typically exhibits a hard excess at high energies. This affects signal reconstruction via subtraction of the background control region measurements in non-trivial ways. Such features represent a significant departure from the canonical picture, and offer novel handles to identify a dark matter signal and to extract underlying dark matter parameters.