Jet Substructure

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Back to Tools_and_Monte_Carlo_Session_1_(SM)#Jet_Physics Jet Physics.

Boosted hadronic decays of massive particles (W,Z,Top,H,BSM..., with session 2) and jet mass/shape studies with QCD jets in early data.

Interested parties (Session 1)

Matt Schwartz, Giacinto Piaquadio, Mario Campanelli, Paulo Francvilla, Jon Butterworth, Peter Loch, Ezio Maina, Leif Lonnblad, Keith Hamilton, Simon Dean, ...

Examine/discuss the different regions of validity for calculations of variables like jet mass, jet width, subjet multiplicity, using e.g. (N)LO ME, PS, matched and resummed calculations etc... (see also A Collection of Matching Benchmarks). Review, compare, critique literature, think about future ideas.

Recent preprint on Zbb and Wbb at NLO.

MC issues

Differences in heavy object decays; different parton showers, matrix element corrections in some MC, not in others; in Herwig, Herwig++, pythia, sherpa. POWHEG improvement soon. See talk from Carlo Oleari Friday afternoon for some discussion of MC@NLO and POWHEG in Higgs decays. Dead cones etc. Keith Hamilton, Giacinto Piacquadio, Matt Schwartz, Leif? to produce a short summary of the effects implemented in different MCs.

How sensitive are the various subjet methods to the above differences?

Detector issues

Pile-up, calorimeter nouse, granularity. Slides from Peter Loch to be linked here.

Studies from GP, MS.

Incomplete set of jet substructure references

* Butterworth+ W/Z+higgs (Cambridge/Aachen)
* Kaplan+ top tagging
* Seymour+ clustering (kT algorithm)
* Butterworth+ WW (kT y scales) 
* The above analysis was carried out with a full detector simulation in the WW scattering chapter (p1769) of this big ATLAS paper.
* Butterworth+ W,Z,H in SUSY cascades (kT y scale again)
* Dokshitzer+ clustering
* Almeida+ and Almeida+ top event shapes
* Butterworth+ neutralinos (kT yscales and Cambridge/Aachen)
* ATLAS public note (SUSY09) on neutralinos from subjet structure
* S. Ellis+ jet pruning, using top as an example
* Krohn+ variable R
* Top ID using kT y scales this Les Houches report (p106)
* Bahr+ Herwig++ manual (includes heavy particle decays)
* Hamilton+ Showers for top decay

Types of object one might use substructure on

  • QCD jets (quark gluon separation)

Wjj provides a sample of quark jets at LHC?

SUSY cascades are rich in quark jets. Could use quark ID to simplify decay chains.

LEP papers.

CDF conference proceedings (2004).

ZEUS paper.

  • Colour singlet heavy objects, two body decay (W,Z,H...)
  • Colour singlet heavy objects, three body decay (Neutralino,...)
  • Coloured heavy objects (top,...)
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