SherpaJetParameters < Sandbox

Samples generated with
   * Sherpa 1.1.3 pp &rarr; jjj (ie. 3 partons, quark or gluons)
   * parton p<sub>T</sub>&ge;20 !GeV/c, |&eta;|&lt;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 &Delta;R 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 &Delta;R between partons to be &ge;0.6, ie. &Delta;R&ge;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>&ge;20 !GeV/c and |&eta;|&lt;2.5 and at least three such jets.
   * I plot the smallest, middle, and largest &Delta;R and &Delta;p in the event. The smallest shows the cut-off due to generator parameters. The middle shows what we would cut on with a &Delta;R cut. Note the different jet &Delta;R/&Delta;p 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

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
pdf	jetd.pdf	r1	manage	42.9 K	2009-12-15 - 20:28	TimAdye	varying D
pdf	jetq.pdf	r1	manage	43.4 K	2009-12-15 - 20:28	TimAdye	varying Qcut

This topic: Sandbox > TWikiUsers > TimAdye > TimAdyeSandbox > SherpaJetParameters
Topic revision: r1 - 2009-12-15 - TimAdye