2015:groups:sm:qg
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2015:groups:sm:qg [2015/06/04 16:51] jesse.thaler [What is the killer app of quark/gluon enrichment?] |
2015:groups:sm:qg [2015/06/04 17:02] jesse.thaler |
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| * Enhancing W/Z/t/H in moderately boosted regime (where we can quark-tag the subjets. | * Enhancing W/Z/t/H in moderately boosted regime (where we can quark-tag the subjets. | ||
| - | ==== 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 define flavor by the Born-level operator contributing to the process. All subtleties are formally power suppressed. | ||
| - | |||
| - | ==== Flavored Jet Algorithms ==== | ||
| - | |||
| - | * This is a topic worthy of its own 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. | ||
| ===== Physics Issues ===== | ===== Physics Issues ===== | ||
| Line 95: | Line 79: | ||
| * 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 ===== | ||
2015/groups/sm/qg.txt ยท Last modified: 2015/07/14 08:27 by philippe.gras
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