Can indirect searches for DM provide insights into candidate particles?

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Discussion Overview

The discussion revolves around indirect searches for dark matter (DM) and the challenges associated with identifying candidate particles such as axions, neutralinos, and sterile neutrinos. Participants explore the methods of detection, the implications of mass differences among candidates, and the limitations of current experimental approaches.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that indirect searches for DM involve detecting bursts of rays from the universe, although the specifics of detection methods are questioned.
  • It is noted that axions, having low masses, may not be detectable in high-energy particle detections, while heavier candidates like neutralinos could be.
  • There is uncertainty about distinguishing between different heavy candidates, such as sterile neutrinos, and whether knowledge of energy scales can guide direct searches.
  • One participant emphasizes that observations of dark matter can help narrow down parameters like mass, decay products, and interactions with normal matter.
  • Another participant discusses the potential for axions to produce photons through specific interactions, raising questions about the visibility of such signals against background radiation like the cosmic microwave background (CMB).
  • Concerns are raised about the detectability of low-energy photons, particularly in relation to the brightness of the CMB.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of indirect searches and the ability to distinguish between various dark matter candidates. The discussion remains unresolved regarding the specifics of detection methods and the implications of different particle properties.

Contextual Notes

Limitations include the dependence on the definitions of dark matter candidates, the unresolved nature of distinguishing between them, and the challenges posed by background radiation in detection efforts.

ChrisVer
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In general, the indirect searches for DM consist of looking at a burst of rays coming from somewhere in the Universe.
Is that correct? Is there any other way?

However, I am not sure how can someone , after seeing such a burst, decide whether it comes from candidate X (let's say neutralino) or candidate Y (let's say axion). Also how are we looking at such a thing [devices/physics]?
 
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Axions have very low masses, while neutralinos have much higher masses. So axions won't show up in high-energy particle detections but neutralinos (or any other thermally-produced dark matter particle) will.
 
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I guess then I should have said some other heavy candidate ,my bad for choosing axions, could I ask the same for sterile neutrinos?
Or is it that you can't distinguish between them, but you have the knowledge then at which energy scale to look into the laboratory [for direct searches]?
 
ChrisVer said:
In general, the indirect searches for DM consist of looking at a burst of rays coming from somewhere in the Universe.
Is that correct? I

No. Some of these detectors aren't even directional.
 
Vanadium 50 said:
No. Some of these detectors aren't even directional.

Meaning? I didn't mean at a specific direction...
 
ChrisVer said:
I guess then I should have said some other heavy candidate ,my bad for choosing axions, could I ask the same for sterile neutrinos?
Or is it that you can't distinguish between them, but you have the knowledge then at which energy scale to look into the laboratory [for direct searches]?
Well, basically the main thing that you'd get is a small piece of the whole picture. The main questions to be answered are:
1. What is the mass of the dark matter particle?
2. What does it decay into?
3. What are its interactions with other matter?

Any observation of dark matter helps to narrow the parameter space available. The ratio of dark matter to normal matter combined with the observation that it's relatively low in temperature give constraints on these quantities, and getting even a little bit of other data would dramatically limit the available options.
 
In general I am trying to write/suggest 2 experimental (1 direct and 1 indirect) ways to search for Dark Matter.
I'm pretty sure about the direct searches, and how to explain them, for almost every popular DM candidate...
However I feel kind of "weak" when it comes to indirect searches.

My idea was to take some particular particle, let's say axions. For the direct searches, the microwave cavities are the most renowned ways for looking into cosmological axions, with which you can look at the open axion-window and get their mass and virial velocity dispersion. Such a signal would be the discovery of the axion.
However the axion can also give photons through the coupling to 2 gammas. So if the axion appears to have (let's say) [itex]m_a \approx 0.1 ~ meV[/itex] would we see a gamma rays coming from some "dark" region with [itex]E_\gamma \approx 0.05 ~meV[/itex] ? But isn't that like direct seeing the axion decay?
 
A photon with 0.1meV of energy would have a wavelength of a little more than 1cm. This is just a bit higher in frequency than the peak frequency of the CMB. Photons of this energy would probably be drowned out by the incredibly bright CMB.
 

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