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List of brainstorming session June 6

Preliminary lists

- (from ER,SP,VC) -

• pt_Z at medium-large pt: few percent precision might require assessing impact of NP corrections; MC study ?
• subleading-log effects in parton showering: find the best variables to test them, and motivate an experimental analysis?
• NNLO+PS: how well do these tools work in regions where logs are large?
• Matching/merging uncertainties in jet substructure analysis: impact on jet-substructure tool performance
• Resonance-aware matching schemes: a comparison could be instructive at this point, possibly in the context of m_top measurements. [can use this study to finally promote the use of the (already existing) LHE-to-PS modern interface capable for example to handle multiple veto-scales]
• A guideline for assessing uncertainties in NLO+PS matching: is this realistic? Can we find a balance between being fully conservative and its opposite?
• EW showers vs. EW corrections at fixed-order: a dedicated comparison?
• g → bbar , g→ ccbar

-(from JH)

• followup on Higgs+jets study from LH2015
  • new study with inclusive jets
  • do parton showers have an impact on inclusive jet cross sections?
  • if all PS do not have a similar behavior, then why
• do we understand in detail variations between various parton showers starting with as similar parameters as possible
  • can we benchmark “true” uncertainties
• comparison of jet shapes at NLO/NNLO, PS and ME+PS
• what is the role of UE when jet area subtraction is universally used

• status wishlist
• to which extent is automation possible?
• availabitity to non-authors
• scale choices
• power corrections
• methods for IR subtractions, e.g. pro's and con's of N-Jettiness
• NNLO+PS (see above)

• scale choices at NLO and NNLO
• how “universal” (/“good”) is HT/2
• scale choices for complex final states
• comparison of power corrections for H+jet to W/Z+jet

• status wishlist
• combination with (N)NLO QCD results (additive, multiplicative)
• inclusion of corrections beyond NLO (multiphoton emission, NLL Sudakov approximation of leading NNLO EW effects)
• uncertainty estimates
• treatment of resolved real-radiation photons (fully inclusive, vetoes)
• public availability

• how to make use of NNLO results

• inclusion of scale uncertainties
• scale choice for inclusive jets (pTjet vs pTjetmax)
• impact of new processes at NNLO (tT, photon+jet, dijet,W/Z+jet)
• dealing with disagreements between observables/experiments

• isolation for photons at NNLO

• NLO+PS can (yet) fully replace the usage of LO+PS in physics analyses ? [practical issues to be discussed]
• Dealing with the large fraction of negative weights
• LO+PS reweighed to NLO+PS, how to (not) do this for specific candles (Z/γ, W)
• scale variations/choices and their interpretation as uncertainties
• VBF (V)V+2j with (N)LO+PS, QCD-EW interference and ME+PS matching, VBF signal definition
• photon+jets and matching with QED/QCD showers, QCD/EW corrections

• LO+PS, NLO+PS, EW corrections on NLO+PS, NNLO+NNLL+PS, NLO QCD+EW + PS
• low/medium PT what combination(s) to use for precision measurements and uncertainty envelopes
• high PT and QCD+EW corrections
• QCD/QED shower corrections + uncertainties at low/medium/high
• resummation

• Closing the loop on quark/quark tagging
  • From the LH 2015 parton shower comparison study…
  • …to a concrete plan of action for LHC jet shape measurements
  • Improved PDF constraints from quark/gluon tagging
• “Deep learning” meets “deep thinking”
  • Interface of machine learning and analytic calculations
  • Multi-category classification
  • Physics-inspired network design
• Jet substructure for tagging
  • Interplay of jet radius, jet grooming, and jet discriminants
  • Tagging longitudinal versus transverse W/Z bosons
  • Impact of soft QCD (underlying event) and pileup
• Groomed jets for precision physics
  • Top mass determination
  • alpha_s extraction from substructure
• Jets and heavy flavor
  • Color flow/dead cone in top quarks
  • Jet substructure of b/c-tagged jets, gluon splitting to heavy flavor
  • Charmonium polarization in identified jets
• Heavy ion physics
  • Jet shapes in medium
  • Probe quark/gluon plasma with boosted objects

• “The Lifetime Frontier at the LHC”: Common language/signature space for displaced vertices.
• “Beyond Missing Energy”: Do we have full coverage (if such a thing can be well-defined ) of BSM signatures which do not involve MET? E.g. R-parity violating SUSY, …
• “Multiple unknowns”: most searches hunt for one new particle (+ MET in SUSY). How difficult is it to expand to multiple unknown particles? Does this add a lot of phase space coverage?
• ' Beyond ATLAS and CMS': BSM at LHCb (and even ALICE). What more can be done with LHCb? Can we find BSM in forward/diffractive physics at all?
• Colliders and multi-component dark matter
• …
• Of course, new ideas or new features from old ideas are always welcome!

-BMS tools and MC (from LP, FM,PR)

• EFT top/Higgs : basis, NLO corrections, applications…
• Dark Matter specific tools: current challenges for s-channel/t-channel simplified models. NLO?
• Recasting/presenting experimental results
• Simplified Models
• MC comparisons in BMS phase spaces (in overlap with SM session)
• Boosted SM objects as probes for BSM searches (in overlap with SM session)

• Heavy flavor modeling (in the context of ttH, overlap with MC and tools)
• Quark-mass effects in inclusive and exclusive distributions (H+(N)j, ZH, HH)
• Simplified template cross sections
  • Status of measurements and review of experience with stage 1 STXS
  • Development towards a more concrete proposal of stage 2
  • Theoretical uncertainties (including correlations)
• Residual uncertainties in fiducial and differential cross section measurements
• Complementarity between non-standard (SUSY) Higgs searches and precision H measurements
• Higgs self coupling
• Probing CP violation in the Higgs couplings
• What are the holes in the searches for additional non-standard heavy Higgs bosons (H→ tt? what are the possible strategies?)
• Searches for very light (ms < mh) scalar particles. Why (theory)? where we are, and where we can be in the future (experiment)?
• Exotic decays of the 125 GeV Higgs. Which decay channels are not covered?
• Pseudo observables and effective theories
• Global picture of naturalness after run1/ first half run2?
• Relaxion
• High-energy versus high precision in Higgs physics?