Samples generated with
• Sherpa 1.1.3 pp → jjj (ie. 3 partons, quark or gluons)
• parton pT≥20 GeV/c, |η|<2.5
• Sherpa's default `JetFinder sqr(QCUT/E_CMS) D` with different values of `QCUT` and `D`. This is a kT algorithm (Sherpa 1.2.0 allows other algorithms, including anti-kT)
• Did not include ΔR cut for these tests, but this can be done using
```"Calc((sqr(DEta(p[0],p[1]))+sqr(DPhi(p[0],p[1]))>=0.36)+
(sqr(DEta(p[0],p[2]))+sqr(DPhi(p[0],p[2]))>=0.36)+
(sqr(DEta(p[1],p[2]))+sqr(DPhi(p[1],p[2]))>=0.36))" 93,93,93 2,3
```
(spacing, included here for clarity, is not allowed in Sherpa's `Run.dat`) which requires at least two of the three ΔR between partons to be ≥0.6, ie. ΔR≥0.6 between one parton and both the other two.
Plots made for 1000 events for various samples (Sherpa examples use Qcut=20, D=1):

• The PDG id is of the 3 partons per event. Do we really expect ~80% of the partons to be gluons, rather than quarks? Bill says yes
• Jet plots are for jets with pT≥20 GeV/c and |η|<2.5 and at least three such jets.
• I plot the smallest, middle, and largest ΔR and Δp in the event. The smallest shows the cut-off due to generator parameters. The middle shows what we would cut on with a ΔR cut. Note the different jet ΔR/Δp samples don't have the same normalisation (especially for Qcut=40,D=1), due to the 3-jet cut.
• The effect of varying Qcut and D shows in the parton separations, but not much in the reconstructed jets. Is the effect really so washed out?
• After hours of LXR/dOxygen searching, I finally found how to run a jet finder on generator output. You need to set a flag to specify the input type: this is done automatically for other input types, but not for generator input. For the record, here's the magic incantation:
```from JetRec.JetRecFlags import jobproperties as jetFlags
jetFlags.JetRecFlags.inputFileType = "GEN"
from JetRec.JetGetters import make_StandardJetGetter
collname = make_StandardJetGetter('AntiKt', 0.4, 'Truth').jetAlgorithmHandle().JetCollectionName```

• jjj
Qcut D nb
5 1 71857
10 1 36939
20 1 19829
40 1 997
20 0.3 70470
20 0.5 41697
20 1.5 7386
• Gbb (no Z)
Qcut D nb
10 1 558
20 1 278
40 1 12
20 0.5 652
20 1.5 91

-- TimAdye - 16-Dec-2009

Topic attachments
I Attachment History Action Size Date Who Comment
pdf jetd.pdf r1 manage 42.9 K 2009-12-16 - 13:44 TimAdye varying D
pdf jetq.pdf r1 manage 43.4 K 2009-12-16 - 13:43 TimAdye varying Q<sub>cut</sub>
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Topic revision: r4 - 2009-12-17 - TimAdye

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