# Les Houches

## 2019 Session

• Working Groups Pages
• Use of wiki. Wifi access/set-up. Printing
• Important info about lodging. Bus. Facilites
• Bulletins.

## Wikis of Previous sessions

#### Les Houches Themes

(Lyrics and Music)

## Help

2019:groups:sm:start

This is an old revision of the document!

# SM Working Group: Loops, Multi-legs and Jets

List of participants (access restricted to the participants only)

#### TOPICS

To be updated * 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

#### Concrete projects

Please add your projects/names to this list

participants: Daniel, Raoul, Alex

#### Jets

We have made a special e-group for anyone who wants to join these discussions: houches-2019-topics-jets. There is also a slack channel: Invite Link. In terms of topics, this is what we have brainstormed so far:

• Where is quark/gluon discrimination actually useful? One complication is that many other analysis selections are already purifying the selection (e.g. requiring two forward jets with large mjj already suppresses gluon jets for VBF/VBS). Examples:
• PDFs
• VBF
• X→gg
• Susy cascades
• ISR tagging
• W tagging
• top tagging
• Extraction of the strong coupling constant This was a main focus of the last Les Houches and we plan on at least having a discussion about this one of the days. As part of this, we may want to do a short study of the difference between inclusive jets (F. Ringer et al.) and dijets.
• Tuning with jet substructure One motivation for performing measurements of jet structure is to improve MC tunes. It would be good to understand which observables are actually sensitive to which parameters, taking note of what has already been measured. IRC safe observables may not be so useful for tuning. Another sub-topic: can we understand the ATLAS jet pull angle measurement from the point of view of parameter variations? (quite significant tension between Pythia and data).
• Can grooming reduce non-perturbative effects? Idea in part suggested by Bogdan Malaescu (see also 1705.07135).
• Tagging There was a big effort to understand light 2-prong tagging last Les Houches. We could revisit this topic for Higgs and/or BSM (top is already quite well-covered with 1902.09914).
• Various ML4Jets topics
2019/groups/sm/start.1560339524.txt.gz · Last modified: 2019/06/12 13:38 by daniel.maitre