LH 2019: Topics for Consideration

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session 1

PDFs:
- dealing with scale uncertainties in PDF fits
- benchmark studies for current generation of PDFs, e.g. top distributions
- dealing with tensions in LHC data, i.e. ATLAS jets vs CMS jets, top distributions
  - does each group have the same reaction to the tensions?
  - how to get the greatest knowledge from distributions with tensions?
- electroweak effects in PDF fits
- dealing with NNLO grids (NNLOJET)

Parton Showers:
- LH17 showed that PS predictions agree well with each other when input parameters are synchronized; reasonable physics choices then lead to differences; can we establish the limit of what these reasonable physics choices are?

ME+PS:
- better understanding of limits of precision for ME/ME+PS calculations
- uncertainties in matching PS with ME
- better understanding of 'reasonable' scale uncertainties at NNLO
- precision predictions in the high pT frontier

Progress with higher order calculations:
- any benchmarking, for example DY at NNLO?
- improvements for evaluation of 2→2 at NNLO
- loopedia
- outlook for 2→3 NNLO
- 3-loop, e.g. Higgs rapidity
- compact expressions at the amplitude level
- ntuples for NNLO

Jets: Where is quark/gluon discrimination useful? How does it perform? Examples:
- PDFs
- VBF
- X→gg
- Susy cascades
- ISR tagging
- W tagging
- top tagging

MC and Tools
- ttbar: mismodeling of top pt and spin correlations. There are tensions between ATLAS and CMS in top distributions. Other variables to look at? Dedicated study performed by MC authors, comprehensive of main uncertainties.
- W-mass and precise EW measurements: where are the bottlenecks? Is the specific ATLAS W-mass tune working well for all observables (y_Z)?
- Vector Bosons scattering: follow up from LH17. Continue “benchmarking” study at NLO, to expose differences due to different approximations made in the NLO computation. NLO+PS: check distributions and make sure all EXP are aware of differences among different generators and showers.
- EW effects in PS. It's known that they are important for HE. Collect/study examples where these effects are relevant, produce some representative plots. LH proceeding can become a reference, as well as a place where the “TH challenge” is stated.
- High performance computing: can we use LH as a platform to initiate some study on performances, negative weights, etc. What are the needs for high-energy pp machines and more in general to future colliders? How should we define a metric?
- Legacy data: what’s the best format, how to make sure TH can easily access it, and even just find the important information for their needs (e.g. for PDF fitters and constraints on EFT). Is HEPDATA enough? Can we use it more efficiently?
- Z+1 jet: distorsion of Z rapidity / PS mapping for radiation.

session 2

Higgs: new physics
- Higgs pairs: lambda_HHH from single & double;
- VBF Higgs pairs: C2v, Cv relation
- Rare decays: benchmark for H→aa→gamgamgamgam
- Rare and exotic Higgs decays: further channels not searched for? motivation in specific BSM scenarios?
- CP violation and Higgs: (HL-)LHC sensitivity, complementarity with other probes (e.g. EDMs)
- Lighter than 125 GeV scalars: how well are they covered by LHC and LEP?
- Interpretation of SM coupling/STXS constraints in BSM benchmarks
- MSSM: how to close the gap in the high mA (>= 500 GeV), intermediate tan(beta) range?
- Precision measurements to sharpen interpretation of Higgs results (W mass, TGCs, W/Z coupling to quarks, CKM …)
- New physics at the high-energy tail of Higgs distributions

Precision physics at the LHC
- Precision measurements of Z and W couplings to quarks
- Lepton flavor violation in W decays
- Measurement of CKM elements
- High-energy tail of Drell-Yan production

New Physics
- VLQs beyond V/Hq decays
- Unconventional signatures
- Complex DM and colliders

Flavour anomalies
- High pT searches connected with the flavour anomalies
- Optimized leptoquark and Z' searches
- Tail of the di-leptons distributions
- …

BSM and Machine Learning
- Determination of model parameters
- 2d/3d/4d Image analysis for HEP e.g. jets
- New Searches with ML (search algorithms, generic searches, automatisation, density estimation, deep networks / auto-encoders etc.)
- Learning Phenomenally predictions (limits, likelihoods, cross sections)
- Generative models for HEP

Tools&MC
- Global fits / recasting / scanning spaces
- Analysis preservation
- LLP and resonance searches
- Simplified likelihoods and EFT explorations
- Beyond EFT: unitarity, exploring the continuum between EFT→full models
- BSM modelling with MC
- Future colliders

Les Houches