Les Houches

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======  Topics for Consideration ======
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**__List of brainstorming session June 6__**

=== Jets ===

  * machine learning
  * comprehensive 2-prong study (non-b tags) (W-boson polarization)
  * alpha_s extraction from jet substructure (white whale) e.g. running at high scales (?)
  * assess complementarity to 3-jet/2-jet ratio (or other canonical observables)
  * use cases of quark/gluon tagging (e.g. in H+jets); use in NNLO?
  * jet substructure for understanding showers
  * J/Psi in jets, hybrid substructure, flavour tagging
  * fat jet definition 


=== parton shower issues ===

  * matching variations
   *study angularities
   *beyond LL uncertainties
   *shower starting scale choice (e.g. consistency conditions, test limits)
  * comprehensive shower tuning (+had+MPI) + PDF order
  * heavy flavour modelling
  * resummation versus fixed order e.g. tT + jets (in jet bins) 
  * study tTbB, scale/shower uncertainties, large differences between generators?
  * non-global observables, colour correlations

=== resonance aware matching (tT) === 
[[ 2017:groups:tools:resonance_aware | wiki]]

=== scale choices ===
  * LH Accord for scale variations? [discussion on: **Thu June 8th,  09h00-10h30**]
  * test case e.g. jet-veto cross section in Drell-Yan (+ N jets)

=== PDFs ===

  * tensions within exp. data sets
  * theory uncertainties

=== EW corrections [discussion on: Fri June 9th, 16h30-18h00] ===

  * automation
  * renormalization
  * treatment of resonances
  * democratic clustering
  * additive/multiplicative
  * scale choice

=== NNLO ===

  * comparison of IR subtraction schemes [discussion on: **Wed June 7th, 10h30-12h30**]
  * Ntuples, grids, non-author use (also for NLO use) [discussion on: **Thu June 8th,  14h00-15h30**]
  * standards for public multi-loop results (e.g. Loopedia) [discussion on: **Fri June 9th, 14h00-16h00**]
  * NNLO+PS

=== Higgs ===

  * simplified template cross sections (STXS Higgs)(also fiducial/differential cross sections) ( [[ 2017:groups:higgs:stxs | wiki ]] )
  * boosted H -> bB 
  * H differential 
  * t/b mass effects
  * (N)NLO di-Higgs, gg -> ZH
  * H total XS
  * off-shell Higgs
  * questions in VBF

=== SM backgrounds for DM searches (V+jets) ===

  * ratio Z/gamma, Z/W [discussion on: **Fri June 9th, 09h00-10h30**]  
  * VH (H->bb), correlated scale variations
  * tT+gamma/Z

=== 4-dim methods ===

=== wishlist update ===

=== Vector boson scattering ===

  * LO vs NLO, MC uncertainties, connection to VBF

**__List of brainstorming session June 15__**

=== Recasting ===
 
  * Long-Lived Particles
  * How to use Correlation information
  * Fastsim vs smearing?
  * Simplified Likelyhood framework
  * Long-Lived Particles
  * Making analysis easier to recast?
  * Analysis description accord
   
=== Long-Lived Particles ===

   * Simplified Models
   * Zoology
   * Displaced vertices and baryogensis
   * Displaced tracks

=== Higgs ===

   * Multiplet structure, LHC e+e-, gravitational waves
   * ggH at high pT 
   * Couplings
   * Interference
   * Long Lived particles from Higgs
   * Light (< 100 GeV) Scalars  (Higgs)
     * new variables
   * Data interpretation
   * BSM Higgs new signals, exotic decays
   * EFT
   * Di-Higgs 
   * BSM Impact
   * EW phase-transition, baryogenesis 
   * Couplings to light fermions
   
=== Dark Matter ===   

   * New Models/Portals and LHC signatures
   * heavy flavour signatures
   * New searches 
   * "Dark" parton showers


=== SUSY ===

   * Low MET
   * RPV
   * High multiplicity

===  Lepton non-universality ===

  * Leptoquarks
  * other?
  * SM explanations
  * Links to DM and g-2

NP@LHCb
     
=== Other ===

   * Vector-like quarks missing signatures
   * Missing resonance signals
   * Radion production @LHC
   * New models in MC?
   * Clockwork
   * Naturalness
       * Neutral Naturalness
   * EFT
       * NLO Tools
   * Strong Dynamics
       * Composite Higgs
   * BSM in top quark physics
   * LHC and flavour in New Physics  
   * CP violation 
   * Light particles
   * Beyond 14 TeV
      * New pheno

**__Preliminary lists (before start of the workshop)__**

==== MC and Tools  ==== 
- (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
==== SM NLO/NNLO ====
 == NNLO (from GH) ==
    * 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)
 == NNLO (additions from JH) ==
    *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
 == NLO EW corrections (from SK) == 
    * 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
 == mixed QCD-EW corrections ==
 == PDFs==
    * how to make use of NNLO results
 == PDFs (additions from JH) ==
    * 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
 == photons ==
    *isolation for photons at NNLO
 == future colliders ==

 
== ME+PS (from KT) == 
    * 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 

== Modelling of W and Z/γ at high, medium and low PT (from KT) == 
   * 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     


== Jet Physics (core dump from Jesse) ==
  * 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
==== BSM  ==== 
 
  * "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)

==== Higgs Physics ====
  * 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?
Les Houches

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