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Multi-W events at the LHC from a Warped Extra Dimension

1. Multi-W events at the LHC from a Warped Extra Dimension. Multi-W events at the LHC. Chris Dennis, Muge Karagoz Unel, Jeff Tseng (Oxford University), Geraldine Servant (CEA/Saclay&CERN) 29 March 2007 XXV Workshop on Recent Developments in HEP & Cosmology, Athens, Greece. MKU. 2.

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Multi-W events at the LHC from a Warped Extra Dimension

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  1. 1 Multi-W events at the LHC from a Warped Extra Dimension Multi-W events at the LHC Chris Dennis, Muge Karagoz Unel, Jeff Tseng (Oxford University), Geraldine Servant (CEA/Saclay&CERN) 29 March 2007 XXV Workshop onRecent Developments inHEP & Cosmology, Athens, Greece MKU

  2. 2 Introduction • Extra Dimensions: Solution to problems in Particle physics, favorite since 1990s • Warped extra dimensions (RS) has been especially popular • Current favourite model building in warped space • Gauge hierarchy problem • Unification • Fermion masses • Cosmology,… Multi-W events at the LHC MKU

  3. 3 Model Specifics • Basic ingredients of model building: • Randall-Sundrum ED for gauge hierarchy • Extended EW gauge symmetry • Original model: RS + SO(10) (Servant&Agashe,hep-ph/0411254), a heavy bR (~1.5 TeV) along with a Dark Matter Candidate • Revised models: embed into SU(2)LxSU(2)RxU(1) (Contino, et al.,hep-ph/0612048) • Additional custodial symmetry in SU(2)LxSU(2)R to protect EW precision observables (Z→bb) from new contributions • Light degenerate KK fermions (“custodians”): with no zero modes bR,L,Q = 2/3, -1/3, 5/3 Multi-W events at the LHC MKU

  4. 4 Strategy • Investigate feasibility of searching for the KK quarks and related signatures through multi-W events • Heavy quark searches at LHC is has become in general a hot topic (see Gokhan Unel’s talk) • Uncommon in SUSY searches for example • Try to stay as inclusive as possible • Preprint: hep-ph/0701158 Multi-W events at the LHC Signature: 4W + 2b-jets MKU

  5. 5 Production • Dominated by pair production (focus in bR – others basically the same, except enhanced EWK coupling) • Main production mechanism is from strong interactions. EWK much smaller. Multi-W events at the LHC MKU

  6. 6 Details of bR Decay • Decay channels: tW, bZ, bH • bRbR→tWtW→ 4W + 2b • If H heavy enough, H→WW can give same signature (not simulated here) • q5/3 are also produced: decay entirely via tW • Simulate only tW decay modes of bR (Q=-1/3) • Scale up by 2(1+B2)/B2 to get total rate including q5/3 • Studying cases with benchmark Higgs masses (300, 115 GeV) Multi-W events at the LHC MKU

  7. 7 Multi-W Backgrounds • Generic form: • n×W + m×[b-jets] + k× [X] • Candidate backgrounds: any associated t and/or W production • tt • ttH, esp. if M(q)>1 TeV with H->WW (similarly tt+n×W) • tttt, negligible by order of 4 below tt • Here we concentrate on ttbar as the dominating background source Multi-W events at the LHC MKU

  8. 8 Multi-W Signature Multi-W events at the LHC • At bR mass of 500 GeV in 10fb-1 of data: • 4000 tW • 700 bH, H→WW (Higgs mass 300 GeV) • At q5/3 mass of 500 GeV: • 22000 tW MKU

  9. 9 Feasibility Study • Count Ws in leptonic and hadronic decays • Purely generator-based • Calchep 2.4.3 + Pythia 6.4.01 (CTEQ6L) • Hadronic jets: • Use charged+neutrals (non-ν) within |η|<4.9 • Seed with pT>1 GeV • Softer tracks added if within ΔR<0.4 of jet centroid • b-jets: hadronic jet closest to generated b • Background sample mostly tt (Toprex 4.11 + Pythia 6.4.03), also some ttH (Pythia) Multi-W events at the LHC MKU

  10. 10 “Trigger” Requirements • Follow standard W leptonic trigger: • e or μ, pT > 25 GeV in |η|<2.4 • Missing ET > 20 GeV Multi-W events at the LHC MKU

  11. 11 S vs B after trigger • pT distributions of decay products (all normalized to unit area) • Will require W pT > 150 GeV signal Multi-W events at the LHC MKU

  12. 12 S vs B after trigger • Require jet pT>20 GeV • 4 hadronic W’s? • Probably semileptonic quark decays Multi-W events at the LHC MKU

  13. 13 S vs B after trigger • Require ΣET>800 GeV, for bR mass of 500 GeV Multi-W events at the LHC MKU

  14. 14 Counting hadronic Ws • Reconstruct W→jj: • Loop over dijet pairs (no leptons) • Add 4-vectors, assuming zero jet mass Multi-W events at the LHC MKU

  15. 15 Distinguishing Multi-W Signal • One W is already identified by lepton • Typical SM events have two W’s (or Z’s) • Eliminate one hadronic W: • When looping over dijets, start from the highest-energy jet • If we find another jet which can make a W mass (70-90 GeV), start plotting with next pair • Method has been tested with W+jets sample to make sure it doesn’t sculpt background distribution • Remaining W’s are mostly from non-SM sources Multi-W events at the LHC MKU

  16. 16 Result in 1 leptonic W • Final comparison, normalized to 10 fb-1 Multi-W events at the LHC MKU

  17. 17 Number of Leptonic Decays • 4 leptons + 2 b’s: suggested as a “golden discovery channel”, although the event yield is extremely low, • but can we distinguish it from SUSY? • However, requiring 2 leptons seems more reasonable to do Multi-W events at the LHC MKU

  18. 18 Dilepton Events • Requiring two leptons mostly eliminates tt background without having to eliminate a hadronic W • This work is in progress Multi-W events at the LHC Same-sign Opposite-sign MKU

  19. 19 Further on q5/3 • Identifying this would be a telltale indication for this model • Unfortunately only leptons have reliable charge information, not jets • Possible analysis: • Select same-sign dilepton events • Exclusively reconstruct bR on other side (similar to ATALS TDR analysis of 4th gen quarks) • Looking into this right now Multi-W events at the LHC MKU

  20. 20 Conclusion & Outlook • Present analysis: • Feasibility study promising • Need more realistic simulation, first steps in ATLAS’s Atlfast • Relating size of W peak to cross section is nontrivial • Could suppress SM backgrounds further by tightening trigger requirements and selecting dileptons • Multi-W/Z events are generically interesting • Recent work on identification using single-jet mass (e.g., Skiba&Tucker-Smith, hep-ph/0701247) • Also Butterworth, et al., for WW scattering identification • Further directions: • q5/3 analysis: the smoking gun • Sensitivity vs mass of bR, Higgs • Exotic, long-lived quarks – CHAMP signatures Multi-W events at the LHC MKU

  21. 21 BACKUP Multi-W events at the LHC MKU

  22. LKP LZP LSP Dirac fermion gauge boson Majorana fermion Z3 KK parity R parity ~ 600GeV – 1000GeV ~ 20GeV – Few TeV ~ 50GeV – 1TeV • LHC • Indirect(Astro) • LHC • Direct(Astro) • Indirect(Astro) • LHC • Indirect(Astro) 22 L?P Dark Matter Candidates nature Multi-W events at the LHC symmetry mass detection MKU

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