"Non-Local" Effects from Boosted Dark Matter in Indirect Detection

TL;DR

This paper explores a novel non-local effect in indirect dark matter detection where boosted dark matter particles can produce gamma-ray signals originating from different locations, affecting the interpretation of observational data.

Contribution

It introduces a new non-local framework for dark matter annihilation signals, highlighting how boosted dark matter can travel and produce signals away from their source, altering astrophysical predictions.

Findings

Non-local $J$-factors differ significantly from traditional models.

Dwarf galaxy signals are suppressed relative to the Milky Way.

This suppression can help reconcile gamma-ray excesses with non-observations.

Abstract

Indirect dark matter (DM) detection typically involves the observation of standard model (SM) particles emerging from DM annihilation/decay inside regions of high dark matter concentration. We consider an annihilation scenario in which this reaction has to be initiated by one of the DMs involved being boosted while the other is an ambient non-relativistic particle. This "trigger" DM must be created, for example, in a previous annihilation or decay of a heavier component of DM. Remarkably, boosted DM annihilating into gamma-rays at a specific point in a galaxy could actually have traveled from its source at another point in the same galaxy or even from another galaxy. Such a "non-local" behavior leads to a non-trivial dependence of the resulting photon signal on the galactic halo parameters, such as DM density and core size, encoded in the so-called "astrophysical" $J$-factor. These non-local $J$-factors are strikingly different than the usual scenario. A distinctive aspect of this model is that the signal from dwarf galaxies relative to the Milky Way tends to be suppressed from the typical value to various degrees depending on their characteristics. This feature can thus potentially alleviate the mild tension between the DM annihilation explanation of the observed excess of $\sim$ GeV photons from the Milky Way's galactic center vs. the apparent non-observation of the corresponding signal from dwarf galaxies.