Development of dark disk model of positron anomaly origin

TL;DR

This paper develops a dark disk model for the positron anomaly in cosmic rays, exploring two- and four-body dark matter annihilation modes with quark contributions, and finds the four-body mode slightly better fits observational data.

Contribution

It introduces a dark disk model with active dark matter components and compares two- and four-body annihilation modes, including quark channels, to improve data fitting.

Findings

Four-body annihilation mode provides a slightly better fit to data.

Optimal dark matter particle masses are around 350 GeV and 500 GeV for 2- and 4-body modes.

Including quark modes enhances data fitting despite expectations.

Abstract

Dark disk model could be a remedy for dark matter (DM) explanation of positron anomaly (PA) in cosmic rays (CR). The main difficulty in PA explanation relates to cosmic gamma-radiation which is inevitably produced in DM annihilation or decay leading to tension with respective observation data. Introduction of "active" (producing CR) DM component concentrating in galactic disk alleviates this tension. Earlier we considered two-lepton modes, with branching ratios being chosen to fit in the best way all the observation data. Here we considered, in framework of the same dark disk model, two cases: two-body final state annihilation and four-body one, and in each case a quark mode is added to the leptonic ones. It is shown that 4-body mode case is a little better than 2-body one from viewpoint of quality of observation data description at the fixed all other parameters (of CR propagation, background, disk height). The values of DM particle mass around 350 GeV and 500 GeV are more favourable for 2- and 4-body modes respectively. Higher values would improve description of data on positrons only but accounting for data on gamma-radiation prevents it because of unwanted more abundant high-energy gamma production. Inclusion of the quark modes improves a little fitting data in both 4- and 2-body mode cases, contrary to naive expectations. In fact, quark mode has a bigger gammas yield than that of most gamma-productive leptonic mode~--- tau, but they are softer due to bigger final state hadron multiplicity.