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2015:groups:sm:qg [2015/06/04 16:37] jesse.thaler |
2015:groups:sm:qg [2015/06/04 17:05] jesse.thaler [Analysis Workflow] |
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a.k.a. Hunting the White Whale of Jet Substructure | a.k.a. Hunting the White Whale of Jet Substructure | ||
+ | * Andy Buckley | ||
* Jon Butterworth | * Jon Butterworth | ||
+ | * Mario Campanelli | ||
* Marat Freytsis | * Marat Freytsis | ||
* Peter Loch <loch@physics.arizona.edu> | * Peter Loch <loch@physics.arizona.edu> | ||
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* Dave Soper | * Dave Soper | ||
* Gregory Soyez | * Gregory Soyez | ||
+ | * Frank Tackmann | ||
* Jesse Thaler <jthaler@mit.edu> | * Jesse Thaler <jthaler@mit.edu> | ||
- | * who did I forget? | + | * ... |
- | + | ||
- | * Remotely: Andy Buckley, Mario Campanelli | + | |
Link to GitHub repository: https://github.com/gsoyez/lh2015-qg | Link to GitHub repository: https://github.com/gsoyez/lh2015-qg | ||
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* ATLAS A14 tune already uses jet shapes, and finds that alpha_s has to be tuned downward in Pythia 8. This, however, has a detrimental effect on LEP measurements, so one has to be cautious about this. | * ATLAS A14 tune already uses jet shapes, and finds that alpha_s has to be tuned downward in Pythia 8. This, however, has a detrimental effect on LEP measurements, so one has to be cautious about this. | ||
* Is there a tuning flat direction? | * Is there a tuning flat direction? | ||
+ | |||
+ | |||
+ | ==== Hemisphere quark/gluon definitions in e+e- ==== | ||
+ | |||
+ | * Consider the case of e+ e- -> q qbar. Partition event into (thrust) hemisphere, define hemisphere flavor by summing over flavors of hemisphere constituents. | ||
+ | * At LO, we can unambiguously define hemisphere flavors. | ||
+ | * At NLO, we can also unambiguously define flavor via hemisphere, though there is now a small gluon fraction from gluon recoiling against q qbar pair. | ||
+ | * At NNLO, things are more complicated. | ||
+ | * Can have soft gluon splitting into q-qbar in different hemispheres, creates IRC safety issue. | ||
+ | * One can use a flavored algorithm (BSZ) to define the flavour of two flavor-kt jets | ||
+ | * Ultimately, want to give an operational definition of flavor based on the Born-level operator contributing to the process. | ||
+ | * Claim: all subtleties are formally power suppressed. | ||
+ | * Use case, VBF, two jets with a third jet veto, q/g well-defined in the exclusive limit. | ||
+ | |||
+ | ==== Flavored Jet Algorithms ==== | ||
+ | |||
+ | * This is a topic worthy of its own Les Houches study. | ||
+ | * For pp collisions, multiple possible uses of flavored jet algorithms. | ||
+ | * One can just run flavor-kT | ||
+ | * Or one can run flavor-kT to define flavor ghosts, and run standard anti-kT. | ||
+ | * Or one can run flavor-kT for deflavoring constituents, and then run standard anti-kT. | ||
===== Ultimate Goal for Les Houches Study ===== | ===== Ultimate Goal for Les Houches Study ===== | ||
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* Do we understand FSR modeling by workhorse parton showers? | * Do we understand FSR modeling by workhorse parton showers? | ||
+ | * Start with the clean case of e+e-, move to pp later. | ||
==== Basic Plan === | ==== Basic Plan === | ||
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* Generalized angularities with soft-drop jets, varying beta_SD | * Generalized angularities with soft-drop jets, varying beta_SD | ||
* Do sum over pairs version of angularities (i.e. ECF-style) | * Do sum over pairs version of angularities (i.e. ECF-style) | ||
+ | |||
+ | ==== Analysis Workflow ==== | ||
+ | |||
+ | * Rivet analysis in place which computes from a HepMC event sample the various generalised angularity distributions. | ||
+ | |||
+ | ==== Questions ==== | ||
+ | |||
+ | * Is discrimination power (e.g. for width) coming from the hadronization regime? | ||
+ | * | ||
===== Next Les Houches Study (for after LH) ===== | ===== Next Les Houches Study (for after LH) ===== | ||