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2015:groups:sm:qg [2015/06/03 16:45] jesse.thaler [Supplemental Jet Shapes] |
2015:groups:sm:qg [2015/06/04 17:07] jesse.thaler [Core Jet Shapes] |
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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 | + | * Peter Loch <loch@physics.arizona.edu> |
* Deepak Kar | * Deepak Kar | ||
- | * Jesse Thaler | ||
* Andrzej Siodmok | * Andrzej Siodmok | ||
- | * Peter Skands | + | * Peter Skands <peter.skands@monash.edu> |
* Dave Soper | * Dave Soper | ||
* Gregory Soyez | * Gregory Soyez | ||
- | * who did I forget? | + | * Frank Tackmann |
- | + | * Jesse Thaler <jthaler@mit.edu> | |
- | * Remotely: Andy Buckley, Mario Campanelli | + | * ... |
+ | Link to GitHub repository: https://github.com/gsoyez/lh2015-qg | ||
===== Preliminaries ===== | ===== Preliminaries ===== | ||
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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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* Question: use ROC curves or mutual information (I(T;A)) to quantify discrimination power? | * Question: use ROC curves or mutual information (I(T;A)) to quantify discrimination power? | ||
* Answer: doesn't really matter, probably I(T;A) is easier to begin with. | * Answer: doesn't really matter, probably I(T;A) is easier to begin with. | ||
+ | * Better answer: Use separation (S-B)^2 / (2 (S + B)). | ||
==== Core Jet Shapes ==== | ==== Core Jet Shapes ==== | ||
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* Question: Sum over particles (angularity-style) vs. sum over pairs (ECF-style) | * Question: Sum over particles (angularity-style) vs. sum over pairs (ECF-style) | ||
* Answer: Sum over particles (angularity-style) | * Answer: Sum over particles (angularity-style) | ||
+ | * Question: Plot linear or log scale? | ||
+ | * Answer: Do both if it makes sense, better for angularities to have log scale. | ||
==== Supplemental Jet Shapes ==== | ==== Supplemental Jet Shapes ==== | ||
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* tau21, or ECF(2,3) | * tau21, or ECF(2,3) | ||
* 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) | ||
+ | ==== 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) ===== | ||
* Above study at hadron colliders, using dijets, W/Z/gamma + j, and maybe t tbar samples | * Above study at hadron colliders, using dijets, W/Z/gamma + j, and maybe t tbar samples | ||
- | ===== Original Notes from Gregory ===== | + | ===== Preliminary plots for meeting on Thursday ===== |
+ | |||
+ | {{:2015:groups:sm:ga_10_20.pdf|}} | ||
+ | {{:2015:groups:sm:ga_10_10.pdf|}} | ||
+ | {{:2015:groups:sm:ga_10_05.pdf|}} | ||
+ | {{:2015:groups:sm:ga_00_00.pdf|}} | ||
+ | {{:2015:groups:sm:ga_20_00.pdf|}} | ||
+ | |||
+ | ===== Notes from Tuesday Meeting ===== | ||
<code> | <code> | ||
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above, +PU, VBF | above, +PU, VBF | ||
[Peter L.] | [Peter L.] | ||
+ | |||
+ | </code> | ||
+ | |||
+ | ===== Notes from Thursday Meeting ===== | ||
+ | |||
+ | <code> | ||
+ | |||
+ | |||
+ | Meeting in Les-Houches | ||
+ | |||
+ | |||
+ | Presentation of the wiki notes: list of contributors, ... | ||
+ | |||
+ | Presentation of the status of the software: | ||
+ | start w e+e- and do pp later | ||
+ | Rivet analysis in place which computes from a HepMC event sample the various generalised angularity distributions | ||
+ | |||
+ | Reminder: what we mean by a q and a g is e+e-\to qq and e+e-\to gg | ||
+ | If we want to do something more refined: | ||
+ | - at LO we can unambiguously sum flavours in hemispheres defined by thrust | ||
+ | - at NLO we can unambiguously sum flavours in hemispheres defined by thrust | ||
+ | we get a quark and a small gluon fraction | ||
+ | - at NNLO things are more complicated. We can use a flavoured | ||
+ | algorithm (BSZ) to define the flavour of each hemisphere | ||
+ | - for pp collisions, we should use a flavoured algorithm to | ||
+ | determine flavour, and then find a way (e.g. using ghosts) to | ||
+ | run anti-kt jets. This would deserve a topic per se (a LH accord)? | ||
+ | |||
+ | - Question: can we match to the Born and find an operatiroal | ||
+ | definition up t power corrections? | ||
+ | Use case: VBF, two jets with a third jet veto. q/g well-defined | ||
+ | in the exclusive limit | ||
+ | |||
+ | Questions to look into: | ||
+ | - is the discrimination power (e.g. for width) coming from the hadronisation regime? | ||
+ | - plotting in log binninb? | ||
+ | - pythia v. herwig important to test string v. cluster hadronisation | ||
+ | - isolate hadronisation regime. Study the scaling in different bins | ||
+ | of one angularity (e.g. thrust). Take a hadronisation region | ||
+ | (T\propto LQCD/Q) and a shower region (T~0.1-0.2) plus optionally a | ||
+ | "hard jet region" (T >~ 0.25) | ||
+ | - does mathing help? | ||
+ | - jet radius dependence (edit analysis and recompile) | ||
+ | - analytic predictions? | ||
+ | for thrust: ee->qq known at N^3LL' + N^3LO | ||
+ | ee->qq known at N^2LL' + N^2LO | ||
+ | ang(bkappa=1): NLL' | ||
+ | - question of the universality/process dependence of the conclusions? | ||
+ | Related to whether the power comes from the core or the periphery? | ||
+ | |||
+ | - process to consider: | ||
+ | mu+mu- -> spin1 -> qq take photons | ||
+ | mu+mu- -> spin0 -> gg take Higgs | ||
+ | for tests of universality | ||
+ | mu+mu- -> spin0 -> qq | ||
+ | |||
+ | - Energies Q=sqrt = 50, 200, 800 GeV | ||
+ | jetdef: ee-antikt [genkt, p=-1], WTA_modp recomb scheme | ||
+ | radii: 0.3, 0.6, 0.9 | ||
+ | |||
+ | - add thrust from thrust hemispheres for analytic purpose | ||
+ | |||
+ | - add multiplicity (event-wide) in bins of thrust: | ||
+ | T < 5 GeV/sqrt(S) | ||
+ | 5 GeV/sqrt(S) < T < 0.1 | ||
+ | 0.1 < T < 0.2 | ||
+ | 0.2 < T | ||
+ | |||
</code> | </code> |