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I'd like to write a paragraph about elementary particles that have been proposed to explain dark matter, but I don't know exactly how to classify these particles or arrange them:

  1. Scaler field

-- Standard model

  1. Axions
  2. Neutrinos
  3. Sterile Neutrinos
  4. Dark photons

-- supersymmetric model (SUSY)

-- Weakly Interacting Massive Particles (WIMPs)

  1. Neutralino
  2. Higgsino
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    $\begingroup$ Try googling for "TASI lectures on dark matter". $\endgroup$
    – knzhou
    Commented Sep 11, 2022 at 5:30

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You will need to pick some property that all models share, and then sort by that. There is no universal rule, and you can choose any property convenient to your situation. Some examples:

  • The year in which the model was first proposed. Good for historical reviews.
  • Alphabetical by name. You can never go wrong with that. Or by the third letter of the second author in the first paper, because why not.
  • Coupling strength under some very specific condition to some very specific target. I'd not recommended that... most have couplings that others don't have so it will be hard to find a common ground.
  • By popularity, i.e. WIMPs, Axions, then the rest.
  • My suggestion: sort them by mass. That makes much sense because mass is a simple scalar number, and because detection techniques greatly vary depending of mass. At the sub-eV scale you're looking for waves, above Planck scale for composite partcles, and even heavier and one has to resort to astrophysical measurements. You will find reviews that are doing just that, notably from the recent SNOWMASS process.

Commenting to your list: Note that there is no standard model candidate for all the dark matter. Neutrinos ARE dark matter but they are hot and there's not enough of them. Consider to add WIMPzillas, Planck-scale relics, and primordial black holes, and perhaps even MACHOs depending on your scope.

Following up on your discussion: Indeed there is a bit of logic hierachy with some of those models. Every higgsino and neutralino is a particular example of a supersymmetric particle. Every lightest supersymmetric particle is an example of a WIMP dark matter candidate. Every WIMP is a thermal relic. The other way around those statements are not correct. Similarly, every QCD axion is a special case of an axion-like particle. But most of your list items are completely independent from each other and thus obey no such hierarchy.

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  • $\begingroup$ OK, but can they be categorized by topics? (models) $\endgroup$ Commented Sep 11, 2022 at 17:02
  • $\begingroup$ Added a bit to that end $\endgroup$
    – rfl
    Commented Sep 11, 2022 at 22:31

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