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W/Z + Jets in the electron channel

W/Z + Jets in the electron channel. Christos Lazaridis Kira Grogg University of Wisconsin-Madison. USCMS First Physics Workshop Fermilab, October 11-13, 2007. W/Z + Jets. Due to high cross section, useful as precise luminosity monitor as a high-statistics detector calibration tool

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W/Z + Jets in the electron channel

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  1. W/Z + Jets in the electron channel Christos Lazaridis Kira Grogg University of Wisconsin-Madison USCMS First Physics Workshop Fermilab, October 11-13, 2007

  2. W/Z + Jets • Due to high cross section, useful • as precise luminosity monitor • as a high-statistics detector calibration tool • to demonstrate performance of CMS experiment • Also good test of pQCD at high Q2 • A QCD regime never probed before! • Boson masses provide necessary hard scale to perform pQCD calculations • W/Z+Jets are irreducible backgrounds • for interesting SM processes(e.g. top production) • for top searches for new physics (SUSY and Higgs searches) Christos Lazaridis USCMS First Physics Workshop

  3. Z Production arXiv:hep-ph/0512167 LHC will probe higher Z pT shedding light on PDF uncertainties Shaded bands are uncertainties for fixed strong coupling strength and varying PDF parameters Christos Lazaridis USCMS First Physics Workshop

  4. W Production Cross Sections W+ W- Shaded bands are uncertainties for fixed strong coupling strength and varying PDF parameters arXiv:hep-ph/0512167 Christos Lazaridis USCMS First Physics Workshop

  5. Datasets • Used data produced for CSA07 • Z+N jets, N = 0…5 • W+N jets, N = 0…5 • Generated with: • ALPGEN 2.12 • GEN-SIM: 1_4_6 • DIGI-RECO: 1_6_0 https://twiki.cern.ch/twiki/bin/view/Main/AlpgenSummer07 Christos Lazaridis USCMS First Physics Workshop

  6. Selecting Zee events Christos Lazaridis USCMS First Physics Workshop

  7. L1 Objects for Z + 0-5 jets Automatic L1 trigger for electrons above 63 GeV Et: 7-bit value in linear scale (.5 GeV bins) max value of 63 GeV max value of 63 GeV Isolated Electron Et Non Isolated Electron Et Christos Lazaridis USCMS First Physics Workshop

  8. Highest Electron Pt Electrons with: • Pt > 15 GeV • -2.4 < η < 2.4 Christos Lazaridis USCMS First Physics Workshop

  9. 2nd Electron Pt Electrons with: • Pt > 15 GeV • -2.4 < η < 2.4 Christos Lazaridis USCMS First Physics Workshop

  10. Z Invariant Mass We can “see” a Z masspeak even with 5 Jets! (in theory) • 2 isolated electrons with Pt > 15 GeV • -2.4 < η < 2.4 Z+0 Jets fit: • Range 80-100 GeV Christos Lazaridis USCMS First Physics Workshop

  11. Removing Electrons from Jets collection Keep jets that don’t have a nearby “electron” within a cone ΔR<0.15… Keep >0.15 …where “electron” is required to havethe ratio 0.85< Pt,electron/Pt,Jet < 1.15 Christos Lazaridis USCMS First Physics Workshop

  12. Highest Jet Pt Some jets (e.g. in Z+0 jets events) are underlying soft QCD radiation • Iterative Cone • Rcone = 0.5 • Pt > 15 GeV • uncorrected • -2.4 < η < 2.4 Christos Lazaridis USCMS First Physics Workshop

  13. 2nd/3rd Highest Pt Jet 2nd Highest Pt Jet 3rd Highest Pt Jet Christos Lazaridis USCMS First Physics Workshop

  14. Reconstructed Pt(Z) Verify theory by comparing data with theoretical predictions that depend on PDFs Christos Lazaridis USCMS First Physics Workshop

  15. Selecting W events Christos Lazaridis USCMS First Physics Workshop

  16. Electron Pt • Pt > 15 GeV • -2.4 < η < 2.4 Christos Lazaridis USCMS First Physics Workshop

  17. Highest Jet Pt Some jets (e.g. in W+0 jets events) are underlying QCD radiation Christos Lazaridis USCMS First Physics Workshop

  18. 2nd/3rd Jet Pt Christos Lazaridis USCMS First Physics Workshop

  19. MET MET ≈ mW/2 Christos Lazaridis USCMS First Physics Workshop

  20. W Transverse Mass cuts: pT,e > 15 GeV MET > 30 GeV Mt,W calculated based on electron and MET information Christos Lazaridis USCMS First Physics Workshop

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