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The WIMP Paradigm: Theme and Variations
by Jonathan L. Feng
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|Authors (as registered SciPost users):||Jonathan Feng|
|Preprint Link:||https://arxiv.org/abs/2212.02479v1 (pdf)|
|Date submitted:||2022-12-06 05:27|
|Submitted by:||Feng, Jonathan|
|Submitted to:||SciPost Physics Lecture Notes|
WIMPs, weakly-interacting massive particles, have been leading candidates for particle dark matter for decades, and they remain a viable and highly motivated possibility. In these lectures, I describe the basic motivations for WIMPs, beginning with the WIMP miracle and its under-appreciated cousin, the discrete WIMP miracle. I then give an overview of some of the basic features of WIMPs and how to find them. These lectures conclude with some variations on the WIMP theme that have by now become significant topics in their own right and illustrate the richness of the WIMP paradigm.
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Excellent introduction to WIMP dark matter.
Strikes good balance of conceptual explanations and more in-depth calculations, equations, etc.
I think a (brief) discussion of the Galactic Center Excess is warranted, especially since the DAMA signal is described in the direct detection sections.
I would recommend publication after a few minor modifications.
1. Although not required, I think a sentence or two about how left-right mixing provides another way to enhance the annihilation of bino-like dark matter would be a good change either at the end of the last sentence on pg. 14 (the sentence just before Section 3.4), or possibly during the stau coannihlation discussion on pg. 16 in Section 3.5. Some possible references are 1707.02460, 2203.08107, 2209.13128 .
2. I think the claim that the bulk region is excluded is only true if there is no left-right mixing, see for example: 1406.4903 .
3. There seems to be an errant comma in Eq. 17
4. Some mention of the different neutrino fogs for different operators might be relevant to give: i.e. 1607.01468.
5. I think the Figure 12 caption should have more explanation as to what each of the lines and shaded regions represent for someone who is not necessarily familiar with these types of plots.
6. I think a sentence should be added explaining that the dark matter direct detection signal is expected to have an annual modulation due to the motion of the earth around the solar system at the beginning of the DAMA paragraph.
7. The sentence that begins “Photons point back to their source” needs to be changed to something similar to: “Since gamma ray photons have such high energies, they travel mostly undeflected and thus point back to their …”
8. In the last paragraph in 4.2 change "photons" to gamma ray photons.
9. As noted above, I think the Galactic center excess deserves some discussion. I would have expected it to have a similar level of discussion as DAMA signal, so maybe a paragraph. But I think at minimum it needs to be mentioned, and maybe a reference to a recent review could be given.
- Cite as: Anonymous, Report on arXiv:2212.02479v1, delivered 2023-01-11, doi: 10.21468/SciPost.Report.6509
Very comprehensive introduction into the topic of WIMP dark matter, excellently written.
- Text overlap with Ref 13 (arXiv:1003.0904) published in Ann. Rev. Astron. Astrophys. by the author of these Lecture Notes.
- Some of the discussed SUSY scenarios are outdated in view of the SM-like Higgs boson with mass of 125 GeV.
These lecture notes are a write-up of Jonathan Feng's lectures on WIMP dark matter at the 2021 Les Houches Summer School, providing a very comprehensive, pedagogical introduction for newcomers to the field. The acceptance criteria (1. subject of ongoing interest to the research community and 2. a correct, systematic and intelligible presentation of the material) are definitely met.
Condensing the vast subject of WIMP dark matter to 36 pages is a difficult undertaking. Clearly, choices had to be made in order to stay concise, and overall this was done in an excellent manner. Nonetheless some additional details might be helpful in some places:
- On page 9, it is mentioned that chemical decoupling is distinct from kinetic decoupling ; a definition of kinetic decoupling and a reference for further reading would be helpful.
- Page 12, last paragraph of section 3.1: the argument that sneutrinos are typically not good dark matter candidates holds for left-sneutrinos, but not necessarily for right-sneutrinos, see Ref ; it would be nice to specify this.
- The CMSSM example, in particular the regions of parameter space shown in Figure 11 ($A_0=0$), is in conflict with the observed Higgs boson mass at 125 GeV; a clarifying comment would be in order.
- Last paragraph on page 16: there are many more ways of relaxing the minimality assumptions: adding a singlet (NMSSM), introducing Dirac instead of Majorana gauginos, adding right-handed neutrino superfields (with and w/o see-saw) etc etc.
- On page 21, the limit of EFT validity would merit a reference.
- Section 5.2: it would be instructive to have an explanation of the origin of isospin violation, or at least a reference to that end (e.g., Gao, Kang, Li, 1107.3529).
- Section 5.4: the minimal GMSB scenario has again a problem with $m_h=125$ GeV; this should at least be mentioned for clarity. After all, the mass of the SM-like Higgs is a prediction, not a free parameter, in these models.
1. The text overlap with Ref 13 should be mitigated or at least pointed out were relevant (or commented in the Introduction).
2. Consider the additional details mentioned in the report (optional apart from the issue of obtaining $m_h=125$ GeV in SUSY models, which should really be pointed out).
- Cite as: Anonymous, Report on arXiv:2212.02479v1, delivered 2023-01-07, doi: 10.21468/SciPost.Report.6474
This is set of lecture notes on WIMP dark matter based on lectures presented by Jonathan Feng at the 2021 Les Houches Summer School. The author is a leading figure in the field, and his own research and thinking on WIMPs has been influential. The subject is presented in an informal and lively manner. It begins by passing down some valuable general advice from our elders to the next generation of researchers, which sets a motivational tone. Much of the material covered is by now standard, including the motivation for WIMPs and the "WIMP miracle", canonical WIMPs in, e.g., supersymmetric models, and standard methods of WIMP detection. However, as the title suggests, connections are also made to close relatives of the WIMP, e.g., inelastic dark matter, WIMPless miracle, etc. It also contains insights that may be somewhat less appreciated today, such as the various motivations for symmetries that can serve a dual purpose of stabilizing WIMPs. At just 30 pages, this set provides a concise and engaging overview of WIMP dark matter which may be read before delving deeper into various technical aspects of Boltzmann equations, direct detection rates, and so on. In summary, this is an excellent and accessible introduction to WIMPs, which nicely complements the other topics in this Les Houches volume. It certainly meets and the standards of SciPost and should be published.
- Cite as: Anonymous, Report on arXiv:2212.02479v1, delivered 2022-12-31, doi: 10.21468/SciPost.Report.6411
1) Well-organized pedagogical approach.
2) Proper balance of rigorous derivation and intuitive motivation.
These lecture notes provide and excellent discussion of the WIMP paradigm, WIMP searches, and non-standard variations on the WIMP paradigm. The discussion of the discrete WIMP Miracle is especially interesting, since, as the author notes, this aspect is underappreciated. The lectures strike the right balance between rigorous derivation and intuitive reasoning. The format and style are appropriate. These lecture notes meet the acceptance standards of the journal.
No changes needed.