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