2023 LHC DM WG Autumn Meeting

53/R-044 (CERN)



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Daniel Johnson (University of Birmingham (GB)), James Frost (University of Oxford (GB)), Matteo Cremonesi (Carnegie-Mellon University (US)), Spyros Argyropoulos (Albert Ludwigs Universitaet Freiburg (DE)), Tim Tait (University of California, Irvine), Uli Haisch, Xabier Cid Vidal (Instituto Galego de Física de Altas Enerxías), Zirui Wang (University of Michigan (US))
LHC DM WG workshop
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Oleg Brandt
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James Frost, Spyros Argyropoulos
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Join via phone
Zoom URL



You said that CMS people are preparing code for simulation. Is that based on public software?

=> Yes


In the top-philic section is the plan to use existing searches? We heard that the team does not have personpower to generate t-channel signals and do a reinterpretation.

=> This will depend on the personpower. If there's not enough that section will only focus on providing benchmarks.


How different is the lepton-philic model  from the SUSY slepton search? 

=> slepton searches can be used to recast these, however there are kinematical differences since the mediator has different spin. This difference will become larger as the width of the mediator increases.


Are there additional signatures that have not been previously explored in lepto-philic models?

=> Benjamin: I don't think there are such signatures, but the topic is interesting because of the existing CMS and ATLAS excesses in the LLP context (small mass splitting)




Is there any plan for having common benchmarks between ATLAS and CMS?

=> some of the signatures that arise in dark showers have been suggested in theory papers and in that case there are some benchmark suggestions but so far there is no common benchmark. This should be addressed in the DM workshop next year. 


was there any discussion about how the phenomenology depends on the number of flavours/colours etc?

=> there are some studies that show that rinv might/might not depent on the choice of flavours/colours. This is important when rinv is treated as an output parameters, since the choice of flavours/colours change the branching ratios. If rinv is set by hand the choice of flavours/colours 



If the number of dark flavours change wouldn’t that affect the runnning of the dark alpha_s and therefore the evolution of the shower?

=> no, once rinv is fixed it effectively selects how the shower evolution is performed


Dark Higgs session:




has it been checked that for the benchmark points chosen there are no constraints from dileptons or dijets?

e.g. https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PUBNOTES/ATL-PHYS-PUB-2023-018/fig_07.png   

this could rule out all solutions for the RD in the off-shell region.

This should be checked

=> Will need to check check constraints from dijet/dilepton searches. 


it seems that most of the points satisfying the RD are in the off-shell region, which means that the met would be low. 

Once the above constraints have been checked, one should check if there is remaining parameter space that satisfies the RD constraints and check how the signal kinematics change.

A different analysis strategy might be necessary to target such benchmarks.



low z’ masses - are there any existing theory or experimental constraints?

=> one should check the constraints from LEP at least for the dark Higgs model. There might also be constraints from electroweak precision. To check this one would need a full realisation of the model. Generally such models are quite constrained.



are there any better theory benchmark to use?

=> models with more scalars including a lepto-philic scalar. Uli will have a look for concrete models and report back



Where does the better obs limit come from?

=> The data deficit has been seen in the 2lqq channel SR, with time-dependency. Right plot on p9


is there any benchmark for which dark Higgs would reach higher mZ’ than dijets?

=> probably in the s->bb final state. it’s being explored.




What is the reason 2-body and 3-body has different trend in terms of the final limit?

=> Mainly from the BR that 3-body decay only opens at high mW’.


Is the model compatible with RD?

=> Thhis has not been checked


Is the W’ coupling flavour-universal?

=> Yes.  in the left-right symmetric model that is used the couplings are flavour universal but one can make an implementation where the W’ couples preferentially to 3rd generation


if it couples flavour universally aren’t there flavour constraints from off-diagonal couplings e.g. b->s transitions? FCNC could arise at loop order 

=> this hasn’t been studied yet




Could charged Higgs results constraining this model?

=> Charged Higgs searches have high b-jet multiplicity since the production goes through pp->tbH+, H+->tb, unlike this signature


are there constraints from W’->WZ/WH

=> this depends on the mixing between the W’ and W, they can be tuned away

There are minutes attached to this event. Show them.
    • 2:00 PM 2:10 PM
      Introduction 10m
      Speakers: Daniel Johnson (University of Birmingham (GB)), Matteo Cremonesi (Carnegie-Mellon University (US)), Spyros Argyropoulos (Albert Ludwigs Universitaet Freiburg (DE)), Tim Tait (University of California, Irvine), Uli Haisch, Xabier Cid Vidal (Instituto Galego de Física de Altas Enerxías), Zirui Wang (University of Michigan (US))
    • 2:15 PM 2:35 PM
      Update on DM t-Channel Signatures [20+10] 20m
      Speaker: Luca Panizzi (Uppsala University)
    • 2:45 PM 3:00 PM
      Preparing the DM roadmap workshop - how to contribute [15+10] 15m


    • 3:10 PM 3:30 PM
      Summary of the "Colours in darkness" dark showers workshop [20+5] 20m


      Speaker: Sukanya Sinha (University of Manchester (GB))
    • 3:35 PM 4:45 PM
      Dark Higgs
      • 3:40 PM
        Searches for low mass dilepton resonances and their interpretation [15+10] 25m


        Speaker: Even Simonsen Haaland (University of Oslo (NO))
      • 4:05 PM
        CMS Dark Higgs Search in the WW Channel [15+5] 20m
        Speakers: Alicia Calderon Tazon (Universidad de Cantabria and CSIC (ES)), Alicia Calderon tazon
      • 4:25 PM
        Hadronic Mono-W′ Probes of Dark Matter at Colliders [15+5] 20m


        Speaker: Kun Cheng (Peking University)