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Di-bosons and Anomalous Couplings aT D0

Di-bosons and Anomalous Couplings aT D0. Heidi Schellman, Northwestern University. Slide on Tevatron context. D Ø Detector. Lepton ID in the D Ø Detector. muon system Coverage to h =2. shielding. electronics. Liquid argon active medium and uranium/copper absorber

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Di-bosons and Anomalous Couplings aT D0

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  1. Di-bosons and Anomalous Couplings aT D0 Heidi Schellman, Northwestern University

  2. Slide on Tevatron context

  3. DØ Detector

  4. Lepton ID in the DØ Detector muon system Coverage to h=2 shielding electronics

  5. Liquid argon active medium and uranium/copper absorber • Hermetic with coverage for:|| < 4.2 • Longitudinal and Transverse segmentation  x  x X0= 0.1x0.1x ~1 • (0.05x0.05 in third EM layer, near shower maximum)‏ Liquid Argon Calorimeter ICR h=1.1 h=1.5

  6. Lagrangian for neutral(ZZγ/Zγγ) □ □ CP conserving → h3,4V couplings (V = γ, Z) Anomalous Allowed g

  7. Lagrangian for charged(WWγ/WWZ) EM gauge inv. (g1γ = 1), C and P conserving  5 couplings:κV, λV, g1Z Allowed Additional Anomalous W/g/Z W/g/Z

  8. Wg and Zg • D0 has excellent photon identification due to fine transverse and longitudinal segmentation in the calorimeter. • Neural network discriminant yields > 90% purity in Zg

  9. Wγ→ lνγProduction PRL 107, 241803 (2011) Radiation 0 (photon ET> 15 GeV, dR(l)> 0.7)

  10. Anomalous Wg couplings 95% CL limits on TGCs:

  11. Zg vvg Phys. Rev. Lett. 102, 201802 (2009) Select interactions with large, significant Missing transverse momentum Zg vvg avoids radiation off of the Z! Limits on the anomalous couplings of Z’s to photons.

  12. Zγ→ llγProduction Phys. Rev. D 85, 052001 (2012) unfolded unfolded Mll > 110 GeV(FSR removal):

  13. Zg mmg 95% CL limits on TGCs Fit the pt distribution to limit anomalous couplings Combine with the nng channel for improved limits. Combine with nng

  14. WZ → lνllProduction Phys. Rev. D 85, 112005 (2012) Three high pT (isolated) leptons (μμμ, eee, eeμ, μμe)+MET SM@NLO: σ = 3.21 ± 0.19 pb (60 < Mll < 120 GeV)

  15. Phys.Rev.D84:011103,2011 ZZ → llll Production • Cross section for the ZZ production using fully leptonic final states • Four high pT leptons (μμμμ, eeee, eeμμ) ZZ → llll 10 events .37 background SM@NLO: σ = 1.40 ± 0.10 pb

  16. ZZ → ννll Production Phys. Rev. D 85, 112005 (2012) 16 • Challenges in ννll final states: • MET reconstruction • WW background Optimal variable is a modified pT with negative corrections proportional to resolutions (ie. pTd < 0) Result: ννll (8.6 fb-1): ZZ → ννll ZZ → vvll SM@NLO: σ = 1.40 ± 0.10 pb

  17. ZZ→ ννll Production Phys. Rev. D 85, 112005 (2012) 17 17 • Challenges in ννll final states: • MET reconstruction • WW background Optimal variable is a modified pT with negative corrections proportional to resolutions (ie. pTd < 0) ZZ → ννll ZZ → vvll SM@NLO: σ = 1.40 ± 0.10 pb Combined: llll (6.4 fb-1)+ννll (8.6 fb-1):

  18. Tevatron WZ and ZZ cross sections ZZ WZ

  19. Summary of Bosons at the Tevatron

  20. Summary • Diboson cross sections have been measured in many all-leptonic channels • Future updates • Full statistics ZZ • Full statistics WW • Anomalous couplings using all channels

  21. BACKUP SLIDES

  22. Older D0 limits on anomalous couplingsfrom Wg, WW, WZ Can be interpreted as measurements of the magnetic dipole and quadrupole moments.

  23. Prospects for the future • D0 and CDF are updating to the full statistical sample. • Done for WZ and ZZ channels • Combining channels and experiments will increase the TGC sensitivity by a factor of 3-5. • LHC experiments have 10 times the cross section  10 fb-1 of data  factor of 10 in statistics and 3 in sensitivity.

  24. Motivation for Diboson Studies • Probe of the EWSB mechanism • Test of the SM • Indirect searches for New Physics Cross sections, Kinematic distributions, Trilinear Gauge Boson Couplings (TGCs) • Important background to: • Top • Higgs • Beyond the SM • Good understanding is highly valuable Proving ground for analysis techniques and statistical treatment used in the TevatronHiggs searches mH < 135 GeV Complementary to Higgs production (same final states/challenges) mH > 135 GeV

  25. D0 – set charged TGC limits using pt in 4 channels WW→lvlv WW lvjj WZ→lvll Wγ→lvγ

  26. Charged Triple Gauge Couplings Probed by WW, WZ, and Wγ production General Lagrangian has 14 parameters Assume EM gauge invariance and C and P conservation ⇒ 5 TGC parameters: g1Z, kγ, kZ, λγ, λZ g1 and k are 1 in the SM, the rest are zero Neutral Triple Gauge Couplings Probed by ZZ and Zg production General Lagrangian has 8 TGC parameters Assume CP conservation ⇒ 4 non-SM TGC parameters: h3γ, h3Z, h4γ, h4Z all 0 in SM

  27. nng candidate event MET g g

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