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I have some trouble in the interpretation of the WIMP cross-section annihilation versus their mass.

Graph

I understand that the lines represent a upper bound on the cross section from the observation. But what do the contours from, e.g., DAMA mean?

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The DAMA collaboration have claimed to have actually detected dark matter, but this is in conflict with the results of other searches. But here one is assuming some model that describes the way dark matter interacts with nuclei and the properties of the dark matter halo. (e.g. spin independent WIMP-nucleus interactions). Then what is going on here is that the DAMA results are consistent with the WIMP mass being in some range and the cross section being in some range, so there will be an area in the figure within which the parameters must be in. However, that area will be in the excluded range of the other searches, as the results from those are inconsistent with the DAMA results.

Now, you can still believe that the DAMA results are correct, because one always has to make assumptions when interpreteting the results of the dark matter searches. E.g. a low mass WIMP is still possible in some models. You can assume that dark matter particles are not WIMPS etc. etc.

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  • $\begingroup$ Whilst models exist that explain DAMA's "signal" but evade e.g. XENON and LUX's limits, they are somewhat contrived IMHO. My impression is that much of the HEP community attributes DAMA's "signal" to an unidentified systematic error. $\endgroup$ – innisfree Jun 6 '14 at 13:09
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    $\begingroup$ @innisfree's interpretation is widely shared, but the thing about DAMA is that they have worked over their kit several times (including replacing large parts of it) and invited outside scientists to have full access to their work and find the problem for them. Despite this no one has found that systematic and the (rather indirect) signal has persisted for many years and now has sky high statistical significance. So it is hard to dismiss completely. However the newer direct dark matter searches like XENON are much lower noise and more direct, so people are more willing to put faith in them. $\endgroup$ – dmckee Jun 6 '14 at 14:54
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    $\begingroup$ And of course the low-background particle physics community still has living memory of Ray Davis' Homestake mine experiment... $\endgroup$ – dmckee Jun 6 '14 at 14:57

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