Galactic positron excess from selectively enhanced dark matter annihilation

Abstract

Precision measurements of the positron flux in cosmic ray have revealed an unexplained bump in the spectrum around E 300 GeV, not clearly attributable to known astrophysical processes. We propose annihilation of dark matter of mass mχ = 780 GeV with a late-time cross section σv = 4.63 × 10 −24 cm 3 s −1 as a possible source. The nonmonotonic dependence of the annihilation rate on dark matter velocity, owing to a selective p-wave Sommerfeld enhancement, allows such a large signal from the Milky Way without violating corresponding constraints from CMB and dwarf galaxy observations. We briefly explore other signatures of this scenario, and outline avenues to test it in future experiments.

Connecting multi-lepton anomalies at the LHC and in Astrophysics with MeerKAT/SKA

“…We note that both AMS-02 anomalies have been widely studied, either as constraints on DM models or as potential signatures thereof [23][24][25][26][27][28][29]. The anti-proton case has been argued to be highly significant and most in agreement with the annihilation via b-quarks of a 40 − 70 GeV WIMP with some potential for heavier masses [23].…”

“…We ensure that measured spectra of the AMS-02 anti-proton results [22] and other constraints are not exceeded. These particular astrophysical data sets are of interest as they have been extensively studied as potential signatures of DM [23][24][25][26][27][28][29][30][31]. This DM model is then used to make predictions for radio observations with the MeerKAT precursor to the Square Kilometre Array (SKA).…”

Consistent explanation for the cosmic-ray positron excess in p-wave Breit–Wigner enhanced dark matter annihilation

“…In our recent work [31] and Ref. [32], the Sommerfeld mechanism is considered to reconcile the contradictions mentioned above, which occurs when the annihilating particles at low velocity self-interact via a long-range attractive potential [33][34][35][36][37][38][39][40][41]. Although the s-wave Sommerfeldenhanced DM annihilation is highly constrained due to the monotonically increasing cross section with decreasing DM velocity [42], the p-wave Sommerfeld-enhanced DM annihilation is still a viable possibility.…”

Constraints on dark matter to dark radiation conversion in the late universe with DES-Y1 and external data

“…The integrated Sachs-Wolfe (ISW) effect has been measured to have an amplitude significantly higher than that predicted in ΛCDM when stacking large voids in the large-scale structure [52,53]; the decrease of dark matter would suppress the Weyl potential on large scales, thus enhancing the ISW effect and could thus help to explain this. Finally, cosmic rays from unidentified sources, specifically the galactic positron excess at ∼300 GeV [54] and the ∼3.5 keV [55] x-ray line from nearby galaxies, have been hypothesized to be sourced by the decay of dark matter [56][57][58][59][60] (although they may be inconsistent with some specific dark-matter particle models [61,62]). All of these lines of inquiry motivate further study of the properties of, and constraints on, the classes of models with DMDR conversion.…”