1 / 21

V+jets and V+hf in HERWIG

V+jets and V+hf in HERWIG. Mike Seymour CERN/University of Manchester Berkeley Workshop March 27 th 2008. V+jets and V+hf in HERWIG. V+jets and V+hf in HERWIG some musings on Andy’s Z+bjet HERWIG results V+jets and V+hf in Herwig++ Status reports HERWIG Herwig++ Rivet/CEDAR.

tahir
Download Presentation

V+jets and V+hf in HERWIG

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. V+jets and V+hf in HERWIG Mike Seymour CERN/University of Manchester Berkeley Workshop March 27th 2008

  2. V+jets and V+hf in HERWIG • V+jets and V+hf in HERWIG • some musings on Andy’s Z+bjet HERWIG results • V+jets and V+hf in Herwig++ • Status reports • HERWIG • Herwig++ • Rivet/CEDAR

  3. V+jet studies in HERWIG • See talks of: • AndreaMessina • Andy Mehta • Jason Nielsen • Michelangelo Mangano (?) • Nils Lavesson • etc (?)

  4. Z/γ+bjet from Tevatron • First a consistency check: • HERWIG6.510, CTEQ6L, inclusive Z (on shell) • parton level: apply +10% correction to σ(Z+b)/σ(Z) • inclusive kt algorithm, R=0.7, massive jets • 1 jet containing b quark with pt>20, |y|<1.5 • and the answer is…

  5. Z/γ+bjet from Tevatron • First a consistency check: • HERWIG6.510, CTEQ6L, inclusive Z (on shell) • parton level: apply +10% correction to σ(Z+b)/σ(Z) • inclusive kt algorithm, R=0.7, massive jets • 1 jet containing b quark with pt>20, |y|<1.5 • and the answer is… 0.20% GOOD !

  6. Z/γ+bjet from Tevatron • Where do these b’s come from? • 0.07% from gluon splitting • ~0.01% from backward evolution to a b! • 0.12% from bb->Z • this is 0.69% of qq->Z, but only 18% of these have a b jet

  7. Z/γ+bjet from Tevatron • Where do the rest of the b’s disappear to? • 60% of b’s do not backward evolve to a gluon: forced (non-perturbative evolution)

  8. Z/γ+bjet from Tevatron • but the other 40% look reasonable:

  9. Z/γ+bjet from Tevatron • Suppose we artificially force b quarks to be evolved back to a gluon perturbatively • i.e. replace forced emission by “abort and reshower” exception •  HERWIG would give 0.38%

  10. Z/γ+bjet from Tevatron • Aside 1: MLM mentioned distortion from ‘abort and reshower’ exceptions: • I find 2.8% of bb->Z events have one • small • acts in opposite direction

  11. Z/γ+bjet from Tevatron • Aside 2: gluon splitting contribution: • LEP measures ~0.3% Z->qq+(g->bb) • PYTHIA predicts ~0.16% • HERWIG predicts ~0.26% • (v. old numbers - need to be checked)

  12. Z/γ+bjet from Tevatron • Conclusion: • More to be understood in backward evolution of b partons, interplay between • modern pdfs: VFNS, current mass • parton showers: massless evolution with constituent mass as infrared cut-off

  13. V+jets and V+hf in Herwig++

  14. HERWIG status • Version 6.510 released October 31st 2005 • Not tuned to data (like all versions 6.1 onwards) ! • Steadily growing list of bugs: • VBF -> Higgs forward-backward asymmetry • B baryon decays • … • Very few promised new features • gg->Higgs ME corrections • W/Z spin correlations in HW/Z production • New release promised “real soon now”

  15. Herwig++ status • Version 2.1.4 released March 3rd 2008 • Version 2.2 coming soon • third digit ~ monthly, second digit ~ twice yearly • Similar quality physics in most areas • Hadronization • Underlying event (Jimmy) • Better in some • Parton shower mass effects (quasi-collinear) • Secondary hadron decays • BSM Simulation (Feynman rules input, spin corr.) • Full tune to e+e- data and Tevatron U.E

  16. Herwig++ status • Complete Physics and Manual • arXiv:0803.0883 [hep-ph] • Hooks for generalized CKKW/MLM matching built in (but nothing hangs from them yet…) • Version 3.0 foreseen for this Fall: complete replacement for HERWIG

  17. CEDAR/Rivet • Combined E-Data Analysis Resource for high-energy physics • HEPdata (database of experimental results) • HEPForge • development environment used by ~ general purpose MCs • LHAPDF • HEPML, RivetGun, AGiLe, … (utilities/interfaces) • JetWeb (web front end for Rivet) • Rivet (object oriented replacement for HZtool) • Experiment-independent implementation of hadron-level analysis for MC standardized comparison

  18. MCnet opportunities 2008: • CTEQ-MCnet school • Short-term studentships: for th. and exptl. students to spend 3-6 months with MC authors in: • CERN • Durham/Cambridge • Karlsruhe • Lund • UCL • on a project of their choice • Next closing date: • March 31st

More Related