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Leptoquark Searches at the Tevatron

Leptoquark Searches at the Tevatron. Daniel Ryan Tufts University. For the CDF and D Ø Collaborations. April 16th, 2004 XII th Deep Inelastic Scattering Workshop Š trbské Pleso, Slovakia. Daniel Ryan. Searches for Leptoquarks at the Tevatron. 2. Outline.

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Leptoquark Searches at the Tevatron

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  1. Leptoquark Searches at the Tevatron Daniel Ryan Tufts University For the CDF and DØ Collaborations April 16th, 2004 XIIth Deep Inelastic Scattering Workshop Štrbské Pleso, Slovakia

  2. Daniel Ryan Searches for Leptoquarks at the Tevatron 2 Outline • “Re”-introduction to CDF and DØ • Introduction to Leptoquarks at the TeVatron • Searches for 1st Generation Leptoquarks • Searches for 2nd Generation Leptoquarks • Summary and Comparison to Run I results • Run II Summary and Future Outlook

  3. p p 1.96 TeV CDF DØ Muon System Central Calorimeter CDF and DØ Run II upgrades Solenoid Silicon Microstrip Tracker Plug Calorimeter Time-of-Flight Drift Chamber Front End Electronics Pipelined Triggers / DAQ Online & Offline Software New Old Partly New Chicago  p Tevatron p Booster p source Main Injector & Recycler

  4. CDF ~ 200pb-1 DØ - 175pb-1 DØ - 104pb-1 CDF - 72pb-1 Feb, 2002 March, 2004 FY '04 Projection: 230 - 310 pb-1 400 300 200 Run I 100

  5. Daniel Ryan Searches for Leptoquarks at the Tevatron 5 Introduction to Leptoquarks Leptoquarks • Spin 0 or 1 and both have lepton and baryon numbers • Color triplet • Fractional Electric Charge • Constraints on FCNC, assume LQ's couple uniquely within a lepton/quark generation u c t quarks d s b ne nµ n leptons e µ t Why study leptoquarks? Some models beyond the SM (GUT's, Technicolor, composite models) assume additional symmetry between leptons and quarks.

  6. e e Daniel Ryan Searches for Leptoquarks at the Tevatron 6 Leptoquark Production at the TeVatron Production qgLQ + LQ* ggLQ + LQ qqLQ + LQ • Pair produced • Independent of l, coupling between LQ's and lepton/quark. *Not shown

  7. Daniel Ryan Searches for Leptoquarks at the Tevatron 7 Leptoquark Production ats = 1.96TeV Run II Run I

  8. Daniel Ryan Searches for Leptoquarks at the Tevatron 8 Leptoquark Decay Each generation can decay into 3 final states:  = 1  = 0.5  = 0 Exclusive to the Tevatron LQ LQ → llqq → 2l+2j BR = 2 LQ LQ → lqq → l+MET+2j BR = 2(1-) LQ LQ →qq→ MET+2j BR = (1-)2

  9. Daniel Ryan Searches for Leptoquarks at the Tevatron 9 1st Generation Leptoquark Searches,  = 1, circa 2003

  10. First Generation Decay 1st Gen. LQ's – ej ej DØ Search – 175pb-1 Daniel Ryan Searches for Leptoquarks at the Tevatron 10 Backgrounds • Drell-Yan+2jets • Top (We) • QCD/Fakes Selection • 2 EM clusters ET > 25 GeV (1 cluster w/ track match) • 2 jets ET > 20 GeV • Z veto (80 < Mee < 102) GeV

  11. DØ – ej ej Daniel Ryan Searches for Leptoquarks at the Tevatron 11 Selection (cont.) • Scalar Sum ST(eejj) > 450 GeV Signal Acceptance ~(10 - 30)% No. Exp. 0.4 ± 0.1 Observed 0 Exclude at 95% CL MLQ<238 GeV/c2

  12. CDF – ej ej Daniel Ryan Searches for Leptoquarks at the Tevatron 12 CDF Selection • 2 electrons (CC,CE) ET > 25 GeV • 2 jets, ET(j1) > 30 GeV, ET(j2) > 15 GeV • Z Veto (76 < Mµµ < 110) GeV • Muon/Jets: ET j1(e1) + ETj2(e2) > 85 GeV • Sqrt( (ET(j1) + ET(j2))2 + (PT(e1) + PT(e2))2 ) > 200 GeV Luminosity 203pb-1 Acceptance (32-42)% Background 6.2+3.1-2.5 Observed 4 Exclude at 95% CL MLQ<230 GeV/c2

  13. 1st Gen. LQ's – ejj CDF Search – 72pb-1 Daniel Ryan Searches for Leptoquarks at the Tevatron 13 Backgrounds • W+2jets • Top (We) • Top (dilepton + jets) CDF Selection • 1 electron (central) ET>25 GeV • MET > 35 GeV • 2 jets ET > 30 GeV • Phi (MET - jet) > 10o • Sum ET(jet1,jet2) > 80 GeV • MT(e,v) > 120 GeV • MET/Sqrt(ET) > 4.5 Signal Acceptance ~(18 - 37)%

  14. CDF – ejj Daniel Ryan Searches for Leptoquarks at the Tevatron 14 Events Expected in 72pb-1 Update in progress... Luminosity 72pb-1 Background 1.7 ± 1.5 Observed 2 Exclude at 95% CL MLQ < 166 GeV/c2

  15. DØ Search –ej j Daniel Ryan Searches for Leptoquarks at the Tevatron 15 DØ Selection • 1 electron (w/ em cluster – track match) ET > 35 GeV • MET > 30 GeV • 2 jets ET> 25 GeV • Phi (MET,jet) > 8o • ST(j1,j2,e,MET) > 330 GeV • MT(e,v) > 130 GeV Signal Acceptance ~(13 - 25)% Luminosity 175pb-1 Background 4.7 ± 0.8 Observed 2 Exclude at 95% CL MLQ < 194 GeV/c2

  16. MET + Jets CDF Search - 191pb-1 Daniel Ryan Searches for Leptoquarks at the Tevatron 16 • Flavor Independent • 1st time for CDF • Channel rich with background • Relies heavily on event topology

  17. MET + Jets Daniel Ryan Searches for Leptoquarks at the Tevatron 17 CDF Selection • 2-3 jets (1st & 2nd leading jets in central region) • Require central jets w/ 4 tracks (rejects  events) • Misaligned jets and MET (rejects QCD, MET from mismeasured jets) (Signal) • MET > 60 GeV • 80< Phi (jet1 – jet2) < 165o • Veto e, µ events Signal Acceptance ~(1 - 8)%

  18. MET + Jets Daniel Ryan Searches for Leptoquarks at the Tevatron 18 Luminosity 191pb-1 Background 118 ± 13 Observed 124 Exclude at 95% CL 78 < MLQ < 117 GeV/c2

  19. Combined Results Daniel Ryan Searches for Leptoquarks at the Tevatron 19 eejj ejj jj eejj ejj DØ Combined: beta = 0.0 MLQ > 98 GeV/c2 beta = 0.1 MLQ > 155 GeV/c2 beta = 0.2 MLQ > 184 GeV/c2 beta = 0.5 MLQ > 213 GeV/c2 beta = 1.0 MLQ > 238 GeV/c2 CDF Combined: beta = 0.0 MLQ > 117 GeV/c2 beta = 0.1 MLQ > 135 GeV/c2 beta = 0.2 MLQ > 161 GeV/c2 beta = 0.5 MLQ > 197 GeV/c2 beta = 1.0 MLQ > 232 GeV/c2

  20. 2nd Gen. --µj µj CDF Search – 198pb-1 Second Generation Decay Daniel Ryan Searches for Leptoquarks at the Tevatron 20 Backgrounds • Drell-Yan+2jets • Fakes • Top (We) CDF Selection • 2 muons with PT > 25 GeV • 2 jets with ET(j1,j2) > 30,15 GeV • Dimuon Mass Veto: 76 < Mµµ < 110, Mµµ < 15 GeV • ET(j1) + ET(j2) > 85 GeV and PT(µ1) + PT(µ2) > 85 GeV • Sqrt( (ET(j1) + ET(j2))2 + (PT(µ1) + PT(µ2))2 ) > 200 GeV

  21. CDF --µj µj Daniel Ryan Searches for Leptoquarks at the Tevatron 21 Luminosity 198pb-1 Background 3.1 ± 1.2 Observed 2 Exclude at 95% CL MLQ < 241 GeV/c2

  22. DØ --µj µj Daniel Ryan Searches for Leptoquarks at the Tevatron 22 Update in progress... Luminosity 104pb-1 Background 1.6 ± 0.5 Observed 1 Exclude at 95% CL MLQ < 186 GeV/c2

  23. 2nd Gen. --µj j in progress Backgrounds • W+2jets • Top (W) • QCD CDF Selection • Muon PT>25, MET>60 GeV • 2 jets, @ ET>30GeV • Veto aligned (Muon, MET) and (MET,jets) • ET(jet1)+ET(jet2) > 80 GeV • MT(MET,Muon) > 110 GeV • MET/Sqrt(ET) > 4.5 Daniel Ryan Searches for Leptoquarks at the Tevatron 23 DØ Run I Limit 180 GeV CDF Run I Limit 164 GeV CDF Run II 200pb-1 Sensitivity ~200 GeV

  24. Daniel Ryan Searches for Leptoquarks at the Tevatron 24 Summary Run 1 Run 2 Beta I II 1 225 200 1/2 204 0 98 98 1 220 202 1/2 182 164 0 1231 Beta I II 1.0 238 200 0.5 213 in progress 0.0 in progressin progress 1.0 230 240 0.5 197 in progress 0.0 117 117 3rd generation not shown 1 c c

  25. Daniel Ryan Searches for Leptoquarks at the Tevatron 25 Summary • CDF and DØ have updated their 1st and 2nd generation direct leptoquark searches using Run II data • DØ has combined results for 1st generation (175pb-1) • CDF has combined results for 1st generation (72pb-1) • No Run II updates on vector leptoquarks from either DØ or CDF. • Work to be done: • CDF and DØ investigating jj channel and DØ investigating qq channel. • 3rd generation leptoquarks. • Vector leptoquarks for Yang-Mills and Minimal type coupling.

  26. Backup Slides

  27. Run I Vector Leptoquark Searches 1st Generation Mass (GeV/c2) Beta Yang-Mills Minimal 1.0 345 290 DØ 0.5 337 282 0.0 298 238 1.0 330 280 CDF0.5 310 265 0.0

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