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Samples generated with * Sherpa 1.1.3 pp → jjj (ie. 3 partons, quark or gluons) * parton p<sub>T</sub>≥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 k<sub>T</sub> algorithm (Sherpa 1.2.0 allows other algorithms, including anti-k<sub>T</sub>) * Did not include ΔR cut for these tests, but this can be done using<br /><verbatim>"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 </verbatim>(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: * [[%ATTACHURL%/jetq.pdf][varying Qcut]]: Q<sub>cut</sub>=5, 10, 20, 40 with D=1 * [[%ATTACHURL%/jetd.pdf][varying D]]: D=0.3, 0.5, 1, 1.5 with Q<sub>cut</sub>=20 Comments: * The PDG id is of the 3 partons per event. Do we really expect ~80% of the partons to be gluons, rather than quarks? * Jet plots are for jets with p<sub>T</sub>≥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 Q<sub>cut</sub>=40,D=1), due to the 3-jet cut. * The effect of varying Q<sub>cut</sub> 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:<verbatim>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</verbatim> -- Main.TimAdye - 2009-12-15
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2009-12-15 - 20:28
TimAdye
varying D
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jetq.pdf
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2009-12-15 - 20:28
TimAdye
varying Qcut
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Topic revision: r1 - 2009-12-15
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TimAdye
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