Les Houches
2023 Session
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- Use of wiki pages and slack. Wifi access/set-up.
- Important info about bus, lodging, facilities.
- Bulletins.
Wikis of Previous sessions
Les Houches Themes
(Lyrics and Music)
(Lyrics and Music)
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a.k.a. Hunting the White Whale of Jet Substructure
* original discussion from 2015-06-02 Generic commentes: ------------------ - ill-defined but OK in the eikonal limit one speaks of quark or gluon-enriched samples - we need an operational definition defined by final-state. e.g. rapidity correlation or shape separate measurement v. interpretation - be worried about the process dependence and the detector effects (MC study v. behaviour in data) - try to speak of a S/\sqrt{B} improvements rather than q/g discrimination [this is also related to the definition of a hadronic W] - can we find a better naming convention? Suggestion: quark-gluon enrichment - Why? Is there a killer app? use q/g as a piece of an analysis general recipe v. optimal analysis - can we use flavoured jet algorithms? - FSR issues (pointed out by Jesse in the introductory talk) related to tuning gluon jets in MC related to colour correlations with ISR [ISR should be sensitive to large angle => see some process-dependence] [FSR should be fimen at small angle => see universality] - Look at hard core v. wide angle. - Experimental results . ATLAS v. CMS: ATLAS suggests beta->0 is not effective CMS says pTD is good . analytics suggest low beta works best . ATLAS sees a large process dependence . is there a connection with ISR? see http://arxiv.org/abs/1405.6583 Appendix A. - Spin information. . is it in the MC? [yes] . does it help or hurt? - g \to qqbar v. g \to gg does it help or hurt - quark v. heavy flavour? Use cases: ---------- - VBF tagging - SUSY multijet is q-enriched - pileup jet rejection (stochastic?) - enhance W/Z/t/H in boosted regime Concrete study(ies) for Les Houches? ------------------------------------ Ideal result: recommendation for experiment for observables that carry info, defined in the final state and define q/g and eventually useful for MC tuning (check the systematics) - A14 tune uses jet shape this brings alphas down Q: what happens to LEP? - 1st study: do we understand FSR modelling? . take e+e- to qqbar and gg . vary energy and jet radius . vary shapes . ROC v. mutual info I(T;A) . use as many MC options as possible shapes: (kappa,beta)=(1 ,0.5) (1 ,1) (1 ,2) (0 ,0) (2 ,0) (0.5,0.5) (0.5,1.5) + ellipticity (+ pull)? + Psi(r) + check Gallicchio and Schwarz . tau21 of ECF(2,3) + ?? on full event or only on tracks? questions: choice of axes (recoil) sum or sum over pairs? . for hadron colliders: look at dijets W/Z/gamma+j ttbar . use groomed jets use soft-drop beta . question of robustness v. performance (including process dependence, pileup, low pt v. high pt) Tasks: ------ - tool writing (jet shapes) use FJ, Rivet professor? [Jesse, Gregory, Deepak] [+Andy B??] - MC for e+e- HERWIG, Pythia, SHERPA [hook Franck, Mark?], VINCIA, ... + options [Peter S, Andrzej] - MC for pp above, +PU, VBF [Peter L.]