Development of dark disk model of positron anomaly origin

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.

Indirect effects of dark matter

“…Positron fraction (a) and corresponding gamma-ray flux in comparison to IGRB (b) for dark disk with cascade annihilation and additional 2(tt) channel. Graphics of gamma from Galactic Center and antiproton fraction from original work[38] are not included.…”

The DAMPE excess and gamma-ray constraints

“…As an example, one can consider a thick dark matter disk emerging from the dissipative dynamics of some subdominant type of self-interacting DM, which also produces high-energy electrons and positrons through annihilations [19, and references therein]. The existence of a thick dark disk is not excluded by the current observations of the dynamics of stars in the Milky Way [89] and if the dark disk is aligned with the baryonic disk the existing gamma-ray constraints on the production of a significant fraction of high-energy e + e − can be also avoided [90,91]. However, in the view of the uncertainties regarding the impact of known astrophysical sources on the total flux of high-energy electrons and positrons and the absence of a well established deficit in them, we find it rather prematurely to advocate this model as an explanation of the spectral features, observed by DAMPE.…”

Cosmic Gamma Ray Constraints on the Indirect Effects of Dark Matter

“…The physical nature of DM still is unknown and it s obviously connected with physics beyond the Standard Model (SM) Many DM search attempts, both direct in underground experiments and accelerator ones and indirect in cosmic ray (CR) experiments are undertaken. We continue our investigations in this field [1][2][3][4][5][6][7][8][9][10].…”