# Dark matter indirect signals with long-lived mediators

## TL;DR

This paper investigates how long-lived mediators from dark matter annihilation alter indirect detection signals, including gamma rays and positron flux anisotropy, and assesses the viability of this scenario for explaining cosmic ray anomalies.

## Contribution

It develops new tools to model mediator propagation effects on dark matter signals and analyzes the impact on fluxes, anisotropy, and the feasibility of explaining cosmic ray anomalies.

## Key findings

- Mediator propagation smears the effective dark matter distribution.
- The $J$-factor is modified by mediator effects.
- Positron anisotropy remains very small, challenging detectability.

## Abstract

Dark matter particles could annihilate into light and metastable mediators subsequently decaying far away from where they are produced. In this scenario, the indirect signatures of dark matter are altered with respect to the conventional situation where standard model particles are directly injected where annihilation happens. We explore here this new phenomenology for which we devise the tools. We calculate the effective dark matter distribution resulting from the smearing by mediator propagation. We derive the fluxes of mediators and their decay particles. We study how the $J$-factor, which naturally appears in the calculation of the dark matter induced gamma ray signal, is modified in the presence of mediators. We also derive the anisotropy which the cosmic ray positron flux exhibits in this scenario. We finally comment upon a recent proposal based on long-lived mediators where the effective dark matter density at the Earth is increased such as to explain the cosmic ray positron anomaly. We conclude that this scenario is barely tenable as regards the very dense dark matter spike which it requires at the Galactic center. The associated positron anisotropy is very small and undetectable, except at high energies where it reaches a level of order $10^{-4}$ to $10^{-3}$.