Can a millicharged dark matter particle emit an observable gamma-ray line?

Abstract

If a gamma-ray line is observed in the near future, it will be important to determine what kind of dark matter (DM) particle could be at its origin. We investigate the possibility that the gamma-ray line would be induced by a slow DM particle decay associated to the fact that the DM particle would not be absolutely neutral. A "millicharge" for the DM particle can be induced in various ways, in particular from a kinetic mixing interaction or through the Stueckelberg mechanism. We show that such a scenario could lead in specific cases to an observable gamma-ray line. This possibility can be considered in a systematic model-independent way, by writing down the corresponding effective theory. This allows for a multi-channel analysis, giving in particular upper bounds on the intensity of the associated gamma-ray line from cosmic rays emission. Our analysis includes the possibility that in the two-body decay the photon is accompanied with a neutrino. We show that, given the stringent constraints which hold on the millicharge of the neutrinos, this is not an option, except if the DM particle mass lies in the very light KeV-MeV range, allowing for a possibility of explanation of the recently claimed, yet to be confirmed, ~3.5KeV X-ray line.

10 pages, references and one figure presenting the bounds holding on the dark charge in the kinetic mixing case added

References in corpus (10)

• Symmetries and Strings in Field Theory and Gravity
• The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data
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• Turning off the Lights: How Dark is Dark Matter?
• Reopening the window on charged dark matter
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• Probing a Very Narrow $Z^{\prime }$ Boson with CDF and D0 Data
• Search for millicharged particles in reactor neutrino experiments: a probe of the PVLAS anomaly

Cited by in corpus (12)

• 7 keV Scalar Dark Matter and the Anomalous Galactic X-ray Spectrum
• SUSY in the sky or a keV signature of sub-GeV gravitino dark matter
• Nonabelian dark matter models for 3.5 keV X-rays
• Decaying Vector Dark Matter as an Explanation for the 3.5 keV Line from Galaxy Clusters
• 3.5-keV X-ray line from nearly-degenerate WIMP dark matter decays
• X-ray Line from the Dark Transition Electric Dipole
• Point Sources from Dissipative Dark Matter
• Exploring X-Ray Lines as Scotogenic Signals
• Displaced Vertices from X-ray Lines
• 3.5 keV Galactic Emission Line as a Signal from the Hidden Sector
• 7 keV sterile neutrino Dark Matter in extended seesaw framework
• Neutral and Millicharged Dark Matter Decay into Gamma-Ray Lines