# Indirect searches for DM

1. Jan 1, 2015

### ChrisVer

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]?

2. Jan 1, 2015

### Chalnoth

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.

3. Jan 1, 2015

### ChrisVer

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]?

4. Jan 1, 2015

Staff Emeritus
No. Some of these detectors aren't even directional.

5. Jan 1, 2015

### ChrisVer

Meaning? I didn't mean at a specific direction...

6. Jan 1, 2015

### Chalnoth

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.

7. Jan 1, 2015

### ChrisVer

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) $m_a \approx 0.1 ~ meV$ would we see a gamma rays coming from some "dark" region with $E_\gamma \approx 0.05 ~meV$ ? But isn't that like direct seeing the axion decay?

8. Jan 1, 2015

### Chalnoth

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.