# Dark Matter "Transporting" Mechanism Explaining Positron Excesses

## TL;DR

This paper introduces a new dark matter mechanism involving long-lived intermediate states that decay near Earth, explaining positron excesses observed by satellite telescopes while avoiding cosmological constraints.

## Contribution

It proposes a novel dark matter transport mechanism with retarded decay, providing a new explanation for positron excesses compatible with existing astrophysical and cosmological constraints.

## Key findings

- The mechanism fits AMS-02 positron data well.
- It avoids conflicts with big bang nucleosynthesis and CMB constraints.
- Provides a generalized source term for diffusion equations.

## Abstract

We propose a novel mechanism to explain the positron excesses, which are observed by satellite-based telescopes including PAMELA and AMS-02, in dark matter (DM) scenarios. The novelty behind the proposal is that it makes direct use of DM around the Galactic Center where DM populates most densely, allowing us to avoid tensions from cosmological and astrophysical measurements. The key ingredients of this mechanism include DM annihilation into unstable states with a very long laboratory-frame life time and their "retarded" decay near the Earth to electron-positron pair(s) possibly with other (in)visible particles. We argue that this sort of explanation is not in conflict with relevant constraints from big bang nucleosynthesis and cosmic microwave background. Regarding the resultant positron spectrum, we provide a generalized source term in the associated diffusion equation, which can be readily applicable to any type of two-"stage" DM scenarios wherein production of Standard Model particles occurs at completely different places from those of DM annihilation. We then conduct a data analysis with the recent AMS-02 data to validate our proposal.