Welcome to the kick-off meeting of the Snowmass Energy Frontier "Dark Matter at Colliders" Topical Group (EF10).
This topical group focuses on Dark Matter and Dark Sector searches at high energy colliders. We will also address the complementarity between the collider searches and other probes of dark matter. More details can be found on our twiki.
The Zoom link is: https://uchicagogroup.zoom.us/j/170161490
Our mailing list is SNOWMASS-EF-10-DARK_MATTER@fnal.gov. To subscribe, send an email to listserv@fnal.gov with an empty subject and the text SUBSCRIBE SNOWMASS-EF-10-DARK_MATTER FIRSTNAME LASTNAME. This also works for other Snowmass mailing lists, including the overall SNOWMASS-ENERGY-FRONTIER-GROUP one.
Live notes (*) for this meeting are now archived at this link. For each meeting, we invite to add points and questions in advance of the meeting in the "Discussion" field, and we can go over them during the discussion. They form the basis for the meeting minutes that will be added to our twiki after each meeting.
To probe the interest of the community, steer our next meetings, and facilitate connections between people interested in similar studies, we have created a questionnaire at this link:
https://forms.gle/KWNZvDuxynHgCyrf6 (please copy and paste the link in your browser, rather than clicking on it)
We will meet roughly every two weeks unless there are other Frontier meetings of interest. The meetings will be held on Thursdays at 12:00 EST/18:00 European Summer time and will generally last one hour, unless we have more requests for contributions. Any presentation is welcome, including work-in-progress: this group's role is to guide and help the community survey the landscape for DM searches at colliders towards the final Snowmass report. The next meeting will be held on June 4th, after the Energy Frontier Kickoff on May 21st.
(*) Live notes is a note-taking practice adopted from the example of the HEP Software Foundation, where points related to the meeting are added in advance of the meeting, and the participants can contribute either before or during the meeting (in the latter case, this is similar to taking minutes/notes, participants still contribute to the live discussion by raising their hand in Zoom and speaking in the meeting). At the end of the meeting, the notes are summarised and published.
Agenda: https://indico.fnal.gov/event/43149/
For archived version of full notes: link
Introduction to the Snowmass process and to this Topical Group:
Snowmass 21 ⊃ Energy Frontier (EF) ⊃ topical group EF10 = Dark Matter at Colliders
How to join and give input:
Mailing list / Slack
Live notes: Link (open for comments before every meeting)
Google Form for EF10: Link
Letter of Interest → Papers, see https://snowmass21.org/announcements
Goals:
DM and dark sector searches at high energy colliders
Will discuss experimental studies of MET+X signatures
For other signatures (eg LLP, visible mediator searches in EF09), liaise with other groups and discuss DM interpretation in EF10
Complementarity between collider searches and other probes of DM
Instruments and experiments considered:
High energy hadron colliders: HL-LHC, HE-LHC, 100 TeV colliders (FCC-hh, SppC)
High energy lepton colliders: FCC-ee, ILC, CLIC, CEPC, muon collider…
Other experiments near/at colliders (in synergy with Rare Processes & Precision Frontier RF06)
Physics topics:
WIMP
Non-WIMP
DM with different portal, mass and coupling range wrt WIMPs
Light DM (e.g. dark photons, dark Higgs)
Strongly interacting DM
Questions: what are the most relevant benchmarks? Are we missing ideas?
Summary plots & contextualization of collider searches:
synergies with many other Frontiers / EF groups
EF10 in general will focus on DM interpretation of models and searches.
In general, work in EF10 will also mean cross-frontier / cross-group - but talk to us and we’ll let you know what the most appropriate “home” for studies is
Coming next:
EF kick-off, May 21st
bi-weekly meetings (alternate weeks with EF09), next on June 4th 12:00 FNAL time
Introduction to the European Strategy process and organization:
European Strategy Update ⊃ BSM Physics Planning Group (PPG) (conveners: Gian Giudice, Paris Sphicas) ⊃ subgroup DM@ colliders (scientific secretaries: C. Doglioni, M. McCullough) / feebly interacting particles, but also contributions to Dark Matter and Dark Sectors Physics Planning Group (conveners: M. Carena, S. Asai)
“Scientific secretaries” of subgroups summarized contributions from collaborations
Each PPG had its own “big questions” - we can take inspiration but make up our own questions for Snowmass
Synergies between ECFA (accelerators, central topic for European Strategy Update), ApPEC (astroparticle) and NuPECC (nuclear physics) encouraged
Choice of benchmarks:
Followed the big question: what cases of thermal WIMPs were uncovered but could be covered by collider searches.
DM@colliders subgroup choices (not exhaustive, but needed to focus around concrete cases):
Higgsino/Wino DM
Higgs portal
LHC DMWG simplified models (vector/scalar mediators) to show interplay of different signatures and searches
Choices from feebly interacting particles subgroup (also concerning beyond-collider experiments) choices include:
Dark Higgs
Dark photon
Results from major future colliders available for nearly all benchmarks above:
Higgs portal interpretation taken from direct and indirect searches studied by Higgs&EW PPG
Highest energy colliders have the best mass reach for new mediators
Lepton colliders have comparable reach in cases where lower background is advantageous (e.g. pure Higgsino, or scalar models)
Synergies and how to put colliders into context
Big question: how non-collider and collider searches could complement/inform each other.
Complementarity: DD/ID probe cosmological DM, colliders probe the DM-SM interaction
Need to choose a model → use same conventions and caveats as LHC Dark Matter WG
Complementarity with both direct and indirect detection
Summary point: huge progress planned from DD/ID, can be followed by future collider program for a comprehensive picture of WIMP DM
Lessons learned, potential topics to develop further:
Improvement in benchmarks
Inclusion of t-channel models, LLP and dark sector models in collaboration with EF09
Improvement of summary plots
Comparison of lepton colliders to DD/ID
Many open topics, discussion needed with Cosmic and Underground Frontiers
Antonio Delgado: Higgsino and Wino already mentioned as benchmarks from SUSY, but there are other multiplets as well (e.g. minimal multiplet, different spins...). It would be good to have benchmarks and studies on those scenarios.
Liantao Wang: it would be good to have those benchmarks. Main differences?
Antonio Delgado: cross-section, but also once beyond the triplet there are objects with a charge 2 or so on that may be long lived.
Jose Zurita: even within the triplet, changing the spin of the DM changes the pT distribution (important for disappearing tracks)
Tim Tait: generalizing spin is important and not hard
Tao Han: studies exist with higher gauge representations, leading to higher dimensional operators and several Higgs fields. This means more parameters.
Liantao Wang: those are still coupling to SM gauge bosons, so it should be easy to deal with the production couplings via simple gauge interactions.
Sabine Kraml: another way of extending beyond minimal SUSY is considering Dirac or Majorana neutralinos, this changes the interplay with direct detection.
Liantao Wang: in simple mediator models, there are qualitative differences between Dirac and Majorana
Liantao Wang: we should keep in mind that for Snowmass we are not planning for a complete exploration of model space but for representative benchmarks
Suchita Kulkarni (via live notes): Higgs portal could include DM production via heavy Higgs. In particular in connection with bbH production mode would also be interesting to explore. For non-WIMPs, It would also be interesting to consider neutrino portal models.
Sungwoo Hong: Trying to understand how to organize the effort (e.g. DM models organized according to whether DM is charged under the SM or portals/hidden valleys). Is there a full list?
Liantao Wang: not yet, we’re open for suggestions
Sungwoo Hong: we could go beyond gauge-invariant local operators. There is some work in progress about e.g. models with global reasons for DM coupling to SM (e.g. shared anomalies, inducing low-energy effective theory interactions)
Antonio Delgado: if we want to go beyond the minimal DM scenarios we could consider coannihilation (e.g.inspired by SUSY, with a singlet and a colored particle)
Liantao Wang: we are considering some SUSY-motivated co-annihilation scenarios
Tim Tait: there are also models with non-tree-level mediation between SM and DM.
Tom Rizzo: Has there been any work done on loop-mediation?
Tim Tait: Yes, e.g https://arxiv.org/abs/1506.01408. What I had in mind was models where there is no tree-level mediation. Everything is intrinsically loop level, which is somewhat different than what Liantao discussed [with loop-level corrections to tree-level indirect detection signal, such as wino and higgsino] … There can be a very different momentum dependence in the loop-mediated models and lead to different phenomenology.
Yu-Dai Tsai: On slide 23, several of the dark photon constraints and projections are not updated. See https://gitlab.com/philten/darkcast for compilation of updates. I can volunteer to help keep the future summary plots updated [email noted]
Caterina Doglioni: this is great, thanks - will also discuss with Rare&Precision frontier subgroup of dark sectors (RP06)
Stefania Gori (convenor of RP06): we are happy to cooperate on dark sector studies with other studies, Phil Ilten is also involved.
Liantao Wang: this could be a topic for one of our future meetings
Jonathan Feng: EF09 sees LLPs as a central topic, whereas it is on the side of this and other groups. It would be good to understand where searches for LLP go, especially FASER/Codex-b/MATHUSLA/etc. It seems these are more central to EF09, but also RF06. It would be nice if a “home” subgroup could be identified so that the relevant activity can be focused and not fall between the cracks (and also so the interested parties don’t have to attend 10 Snowmass meetings each week!)
Caterina Doglioni: LLPs at colliders are indeed within the remit of EF09 and here we focus on the DM connection with LLPs. For low-energy experiments, there is RP06.
Stefania Gori: Following up on the previous discussion, this is the group that Mike Williams and I are convening: https://snowmass21.org/rare/dark There will be coordination with this group. We will also announce a kickoff meeting soon.
[general agreement]: to reduce the number of meetings that need to be attended, we will try to set up joint meetings, assisted by the conveners and official liaisons between frontiers
Meenakshi Narain (EF convenor): we’ve tried to understand the overlap, realizing that cross communication is necessary but the ownership of a given topic has to be within one topical group. This is where the discussions will be nucleated and this minimizes the number of overall meetings. For LLP at colliders, EF09 takes ownership, but clearly communication with EF10 (DM interpretations) and EF08 (model-specific searches and other model-based interpretations) is needed. EF10 will Interpretations is what the DM group will do. We are very mindful of the efficient use of time.
Zhen Liu (convener of EF09): we really value the time of the community, and in the next few biweekly meetings we will probably organize by topic. When it comes to LLP, we will coordinate with the other groups to make sure the other interested parties can join. We will assign themes for each meeting.
Giordon Stark: note that one thing we can try to encourage now for the Run-2 pMSSM scans from ATLAS and CMS is to incorporate more DM constraints in the SUSY reinterpretations, to show the parts of parameter space that can guide future colliders in light of Run-2
Liantao Wang: this is something that the collaborations should certainly do.
Caterina Doglioni: Snowmass can have a facilitating role there. If we plan that we would like to have a particular scenario studied for the projections, we can go back to the collaborations and encourage them to include those scenariosThe collaborations should have some extra guidance to benefit future plans. It will take a bit of time before we are able to say we want to go in a particular direction as we’re still gathering inputs.
Suchita Kulkarni (via live notes): for these scans, we can also consider heavy Higgs to susy decays (e.g. see https://inspirehep.net/literature/1781031, also works by Stefania Gori, Nazila Mahmoudi etc.)
Carlos Wagner: One of the topics that I don’t know if it has been discussed (I was late) is the possibility of CP violation in the interaction between the Dark sector and the Standard one. This could be well motivated if the Dark sector has anything to do with the origin of the baryon asymmetry. This can have important consequences for direct detection, for instance.
Liantao Wang: CP violation has not been discussed yet, important topic to discuss
Carlos Wagner: somebody commented that this is more appropriate to EF09, but I think it is very difficult to decide. This has an impact on what you can say about DD and also on collider physics. It is well-motivated and should be taken into account.
Liantao Wang: we will discuss this in a cross-group meeting and we will focus on the DM interpretation (this also connects to the underground frontier)
Marcus Hohlmann: what is the ratio of theorists to experimentalists in the WG?
Caterina Doglioni and Liantao Wang: there’s a pretty good split for now
Antonio Delgado: More participation of experimentalists would be good, most of the people who have spoken up are theorists
Caterina Doglioni: it is likely that experimentalists are still organizing within the collaboration, so they will be giving input at a slightly later date
Liantao Wang: Reminder: please fill in the google form to give us your input, thanks for participating and looking forward to working together in the future.