An alternative interpretation for cosmic ray peaks

TL;DR

This paper introduces a dark matter-based mechanism involving two species and an extended dark sector to explain sharp peaks in cosmic ray spectra, successfully fitting observed gamma-ray and X-ray excesses.

Contribution

It proposes a novel dark matter scenario with an intermediate decay process that naturally produces sharp spectral peaks, improving upon previous models.

Findings

Successfully reproduces 130 GeV gamma-ray line spectrum.

Accurately models 3.5 keV X-ray line spectrum.

Provides analytical relations between mass parameters and spectral shape.

Abstract

We propose an alternative mechanism based upon dark matter (DM) interpretation for anomalous peak signatures in cosmic ray measurements, assuming an extended dark sector with two DM species. This is contrasted with previous effort to explain various line-like cosmic-ray excesses in the context of DM models where the relevant DM candidate directly annihilates into Standard Model (SM) particles. The heavier DM is assumed to annihilate to an on-shell intermediate state. As the simplest choice, it decays directly into the lighter DM along with an unstable particle which in turn decays to a pair of SM states corresponding to the interesting cosmic anomaly. We show that a sharp continuum energy peak can be readily generated under the proposed DM scenario, depending on dark sector particle mass spectra. Remarkably, such a peak is robustly identified as half the mass of the unstable particle. Furthermore, other underlying mass parameters are analytically related to the shape of energy spectrum. We apply this idea to the two well-known line excesses in the cosmic photon spectrum: 130 GeV gamma-ray line and 3.5 keV X-ray line. Each observed peak spectrum is well-reproduced by theoretical expectation predicated upon our suggested mechanism, and moreover, our resulting best fits provide rather improved chi-square values.