Novel spectral features in MeV gamma rays from dark matter

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

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Spectral features in gamma-rays expected from millisecond pulsars

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.2000.03662.x ◽

2000 ◽

Vol 317 (1) ◽

pp. 97-104 ◽

Cited By ~ 38

Author(s):

T. Bulik ◽

B. Rudak ◽

J. Dyks

Keyword(s):

Gamma Rays ◽

Spectral Features ◽

Millisecond Pulsars

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DARK MATTER SEARCH WITH GAMMA RAYS: THE EXPERIMENTS EGRET AND GLAST

International Journal of Modern Physics A ◽

10.1142/s0217751x02011321 ◽

2002 ◽

Vol 17 (12n13) ◽

pp. 1829-1840 ◽

Cited By ~ 9

Author(s):

ALDO MORSELLI

Keyword(s):

Dark Matter ◽

Cosmic Rays ◽

Standard Model ◽

Supersymmetric Standard Model ◽

Minimal Supersymmetric Standard Model ◽

Gamma Rays ◽

Galactic Center ◽

Direct Detection ◽

Model Parameters ◽

Dark Matter Search

The direct detection of annihilation products in cosmic rays offers an alternative way to search for supersymmetric dark matter particles candidates. The study of the spectrum of gamma-rays, antiprotons and positrons offers good possibilities to perform this search in a significant portion of the Minimal Supersymmetric Standard Model parameters space. In particular the EGRET team have seen a convincing signal for a strong excess of emission from the galactic center that have not easily explanation with standard processes. We will review the achievable limits with the experiment GLAST taking into accounts the LEP results and we will compare this method with the antiproton and positrons experiments, the direct underground detection and with future experiments at LHC.

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