Towards an LHC DM WG white paper on models with 𝒕-channel production of DM @ LHC (LHC DM WG public meeting)

Wednesday 26 Jun 2019, 16:00 → 18:00 Europe/Zurich

31/2-029 (CERN)

Christian Ohm (KTH Royal Institute of Technology (SE)), Oleg Brandt (Ruprecht Karls Universitaet Heidelberg (DE)), Philip Coleman Harris (Massachusetts Inst. of Technology (US)), Tim M.P. Tait (University of California, Irvine), Ulrich Andreas Haisch (University of Oxford (GB)), Xabier Cid Vidal (Instituto Galego de Física de Altas Enerxías)

26.06.2019 t-channel first meeting

Legend:

• Q: question

• A: answer

• C: comment

• AI: action item

Minutes:

• intro (Christian)

• DMsimp (Luca)

  • Q/p3: sensible to have LH and RH couplings at the same time?

  • Q/p4: F3S?

  • Q/p5: “NLO should be added by hand” for DD: what does it mean? Why difficult for DD but not ID?

    • A: for RD, MadDM can’t do NLO automatically

  • Q: currently working on implementing NLO, what are the hurdles?

    • A: some subtleties, at colliders pp → DMDM+j because of t-channel resonant processes, needs care when using the resonance subtraction scheme, Benjamin is testing it

  • Q: how could we map e.g. Tim’s paper or other papers to this model? (e.g. by comparing Lagrangians)

    • A: easy to map through Lagrangians, though specific coupling choices may be different.

  • Q: did not see a link in the talk, could you share it already now? Then others can start playing around with it.

    • A: plan is to make it public very soon, would like to check NLO part

    • Q: is the LO implementation OK (from a physics perspective)?

      • A: yes

    • AI: make UFO public so that other teams can map their results to that. It can be also a preliminary version that can do LO only, still valid for general conclusion. LHC DM can assist (e.g. using its git area)

• Report on the implementation by Haipeng et al. (Haipeng)

  • Q: are you comfortable sharing it on git?

    • A: yes, in a few days

      • C: please circulate the link once available

  • Q: is it a LO UFO?

    • A: yes

  • Q: is the model identical to the S3M_uni and S3D_uni implementation of DMsimp?

    • A: I think so, for RH u quarks

  • Q: how do you plan to prove that the two map to each other?

    • A: first check total xsecs (most straight forward), then differential distributions at parton level

• General discussion:

  • Q: Are there any more UFOs available besides the two presented today and the other two used by ATLAS and CMS?

    • A: Kirtiman & Tim happy to help validating the Über-UFO against their own implementation (but would rather not share it)

    • A: Laura, Jerome, Michel have Feynrules for their implementation, but UFO file exists and has to be found; there will be some overlap in functionality and can help with testing that

      • AI: find + make UFO shared? LHC DM can assist (e.g. using its git area)

    • A: no conclusive answer possible for people/groups not represented here in person

  • Q: does scalar DM give different physics?

    • C: in RD, a clear difference due to different number of annihilation diagrams

      • C: this comes from additional diagrams (3-body interaction, d-wave vs p-wave)

    • C: at colliders, scalar DM can give a sizeable difference in rates, possibly also distributions

    • C: I think this can be quite different at colliders, for scalar DM mediator and fermion DM through different production mechanisms

  • Q: order of magnitude of cross sections for collider signatures similar, don’t expect qualitative difference between different types of DM (Dirac, Majorana, scalar, vector)

    • C: larger importance of t-channel diagrams for scalars

    • C: difference through mediator width + because of different helicity suppressions → would be good to compare basic kinematics at truth level

• Conclusions:

  • AI: will share UFOs that are available (wherever authors comfortable with sharing)

  • AI: will share the DMSimp_t UFO:

    • ~now: preliminary version for LO now so that people can start looking into it

    • once NLO validated: final version

  • AI: compare different UFOs for representative scenarios:

    • cross-sections

    • differential distributions

  • AI: systematically study qualitative differences from different choices for nature of DM (Dirac, Majorana, scalar, vector)

  • AI: next meeting end of July

16:00 → 16:15 Inroduction

Goals of the meeting and outline of plan towards white paper.

Speakers: Christian Ohm (KTH Royal Institute of Technology (SE)), Oleg Brandt (Ruprecht Karls Universitaet Heidelberg (DE)), Philip Coleman Harris (Massachusetts Inst. of Technology (US)), Tim M.P. Tait (University of California, Irvine), Uli Haisch, Ulrich Andreas Haisch (University of Oxford (GB)), Xabier Cid Vidal (Instituto Galego de Física de Altas Enerxías)

LHC DM WG t-channel meeting 2019-06-26.pdf

16:15 → 16:45 Progress on Über-UFO

16:45 → 17:05 Progress on comparing sensitivity for different LHC signatures

17:05 → 17:35 Discussion: how we organize the work moving forward

Discussion where we decide on how to organize the work going into the paper. What can be factorized? What can go in parallel? Probably good to organize smaller meetings for those working on the same parts.