Phenomenology of Dark Matter annihilation into a long-lived intermediate state

TL;DR

This paper introduces a dark matter model where annihilation into a long-lived intermediate state disperses signals, reconciling cosmic ray excesses with gamma ray constraints, and explores implications for collider detection.

Contribution

It proposes a novel dark matter annihilation scenario involving a long-lived intermediate state that explains cosmic ray excesses while satisfying gamma ray constraints.

Findings

Long-lived intermediate state disperses gamma ray signals.

Model explains PAMELA, ATIC, and FERMI excesses.

Decay length linked to high-scale physics (~10^{13} GeV).

Abstract

We propose a scenario where Dark Matter (DM) annihilates into an intermediate state which travels a distance $\lambda \equiv v/\Gamma$ on the order of galactic scales and then decays to Standard Model (SM) particles. The long lifetime disperses the production zone of the SM particles away from the galactic center and hence, relaxes constraints from gamma ray observations on canonical annihilation scenarios. We utilize this set up to explain the electron and positron excesses observed recently by PAMELA, ATIC, and FERMI. While an explanation in terms of usual DM annihilations seems to conflict with gamma ray observations, we show that within the proposed scenario, the PAMELA/ATIC/FERMI results are consistent with the gamma ray data. The distinction from decay scenarios is discsussed and we comment on the prospects for DM production at LHC. The typical decay length $\lambda \gtrsim 10$ kpc of the intermediate state can have its origin from a dimension six operator suppressed by a scale $\Lambda \sim 10^{13}$ GeV, which is roughly the seesaw scale for neutrino masses.