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Leptoquark Searches at the Tevatron April 16th, 2004 XII th Deep Inelastic Scattering Workshop Štrbské Pleso, Slovakia For the CDF and DØ Collaborations.

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Presentation on theme: "Leptoquark Searches at the Tevatron April 16th, 2004 XII th Deep Inelastic Scattering Workshop Štrbské Pleso, Slovakia For the CDF and DØ Collaborations."— Presentation transcript:

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

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

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

4 CDF ~ 200pb -1 Feb, 2002March, 2004 DØ - 175pb -1 FY '04 Projection: pb -1 FY '04 Projection: pb -1 CDF - 72pb -1 DØ - 104pb -1 Run I

5 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 Introduction to Leptoquarks 5 Daniel RyanSearches for Leptoquarks at the Tevatron Why study leptoquarks? Some models beyond the SM (GUT's, Technicolor, composite models) assume additional symmetry between leptons and quarks. u u e e d d c c s s t t b b µ µ   e e µ µ   quarks leptons

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

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

8 Leptoquark Decay Each generation can decay into 3 final states:  = 1  = 0.5  = 0 8 Daniel RyanSearches for Leptoquarks at the Tevatron LQ LQ → llqq→2l+2jBR =   LQ LQ → l qq→l+MET+2jBR = 2  (1-  LQ LQ → qq→MET+2jBR = (1-   Exclusive to the Tevatron

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

10 1 st Gen. LQ's – ej ej DØ Search – 175pb Daniel RyanSearches for Leptoquarks at the Tevatron Backgrounds  Drell-Yan+2jets  Top (W  e )  QCD/Fakes Selection 2 EM clusters E T > 25 GeV (1 cluster w/ track match) 2 jets E T > 20 GeV Z veto (80 < M ee < 102) GeV First Generation Decay

11 DØ – ej ej No. Exp. 0.4 ± 0.1 Observed 0 Exclude at 95% CL M LQ <238 GeV/c 2 11 Daniel RyanSearches for Leptoquarks at the Tevatron Selection (cont.) Scalar Sum S T (eejj) > 450 GeV Signal Acceptance ~( )%

12 12 Daniel RyanSearches for Leptoquarks at the Tevatron CDF – ej ej Luminosity203pb -1 Acceptance(32-42)% Background Observed4 Exclude at 95% CL M LQ <230 GeV/c 2 CDF Selection 2 electrons (CC,CE) E T > 25 GeV 2 jets, E T (j1) > 30 GeV, E T (j2) > 15 GeV Z Veto (76 < M µµ < 110) GeV Muon/Jets: E T j1(e1) + E T j2(e2) > 85 GeV Sqrt( (E T (j 1 ) + E T (j 2 )) 2 + (P T (e 1 ) + P T (e 2 )) 2 ) > 200 GeV

13 CDF Selection 1 electron (central) E T >25 GeV MET > 35 GeV 2 jets E T > 30 GeV  Phi (MET - jet) > 10 o Sum E T (jet1,jet2) > 80 GeV M T (e,v) > 120 GeV MET/Sqrt(  E T ) > 4.5 Signal Acceptance ~( )% 13 Daniel RyanSearches for Leptoquarks at the Tevatron Backgrounds  W+2jets  Top (W  e )  Top (dilepton + jets) 1 st Gen. LQ's – ej j CDF Search – 72pb -1

14 Luminosity72pb -1 Background1.7 ± 1.5 Observed2 Exclude at 95% CL M LQ < 166 GeV/c 2 CDF – ej j 14 Daniel RyanSearches for Leptoquarks at the Tevatron Events Expected in 72pb -1 Update in progress... Update in progress...

15 DØ Selection 1 electron (w/ em cluster – track match) E T > 35 GeV MET > 30 GeV 2 jets E T > 25 GeV  Phi (MET,jet) > 8 o S T (j1,j2,e,MET) > 330 GeV M T (e,v) > 130 GeV Signal Acceptance ~( )% 15 Daniel RyanSearches for Leptoquarks at the Tevatron DØ Search – ej j Luminosity175pb -1 Background4.7 ± 0.8 Observed2 Exclude at 95% CL M LQ < 194 GeV/c 2

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

17 MET + Jets 17 Daniel RyanSearches for Leptoquarks at the Tevatron CDF Selection 2-3 jets (1 st & 2 nd 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) < 165 o Veto e, µ events Signal Acceptance ~(1 - 8)%

18 18 Daniel RyanSearches for Leptoquarks at the Tevatron Luminosity191pb -1 Background118 ± 13 Observed124 Exclude at 95% CL 78 < M LQ < 117 GeV/c 2 MET + Jets

19 CDF Combined: beta = 0.0 M LQ > 117 GeV/c 2 beta = 0.1 M LQ > 135 GeV/c 2 beta = 0.2 M LQ > 161 GeV/c 2 beta = 0.5 M LQ > 197 GeV/c 2 beta = 1.0 M LQ > 232 GeV/c 2 eejj e jj jj jj Combined Results DØ Combined: beta = 0.0 M LQ > 98 GeV/c 2 beta = 0.1 M LQ > 155 GeV/c 2 beta = 0.2 M LQ > 184 GeV/c 2 beta = 0.5 M LQ > 213 GeV/c 2 beta = 1.0 M LQ > 238 GeV/c 2 19 Daniel RyanSearches for Leptoquarks at the Tevatroneejj e jj

20 20 Daniel RyanSearches for Leptoquarks at the Tevatron 2 nd Gen. -- µ j µj CDF Search – 198pb -1 Second Generation Decay Backgrounds  Drell-Yan+2jets  Fakes  Top (W  e ) CDF Selection 2 muons with P T > 25 GeV 2 jets with E T (j1,j2) > 30,15 GeV Dimuon Mass Veto: 76 < M µµ < 110, M µµ < 15 GeV E T (j 1 ) + E T (j 2 ) > 85 GeV and P T (µ 1 ) + P T (µ 2 ) > 85 GeV Sqrt( (E T (j 1 ) + E T (j 2 )) 2 + (P T (µ 1 ) + P T (µ 2 )) 2 ) > 200 GeV

21 21 Daniel RyanSearches for Leptoquarks at the Tevatron Luminosity198pb -1 Background 3.1 ± 1.2 Observed2 Exclude at 95% CL M LQ < 241 GeV/c 2 CDF -- µj µj

22 Luminosity104pb -1 Background1.6 ± 0.5 Observed1 Exclude at 95% CL M LQ < 186 GeV/c 2 DØ -- µj µj Update in progress... Update in progress Daniel RyanSearches for Leptoquarks at the Tevatron

23 23 Daniel RyanSearches for Leptoquarks at the Tevatron 2 nd Gen. -- µj j in progress CDF Selection Muon P T >25, MET>60 GeV 2 E T >30GeV Veto aligned (Muon, MET) and (MET,jets) E T (jet1)+E T (jet2) > 80 GeV M T (MET,Muon) > 110 GeV MET/Sqrt(  E T ) > 4.5 Backgrounds  W+2jets  Top (W  )  QCD DØ Run I Limit180 GeV CDF Run I Limit164 GeV CDF Run II 200pb -1 Sensitivity~200 GeV

24 Summary 24 Daniel RyanSearches for Leptoquarks at the Tevatron Beta I II / / Beta I II / / Beta I II in progress 0.0 in progressin progress in progress Beta I II in progress 0.0 in progressin progress in progress c c 3 rd generation not shown Run 1Run 2

25 Summary 25 Daniel RyanSearches for Leptoquarks at the Tevatron  CDF and DØ have updated their 1 st and 2 nd generation direct leptoquark searches using Run II data  DØ has combined results for 1 st generation (175pb -1 )  CDF has combined results for 1 st 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.  3 rd generation leptoquarks.  Vector leptoquarks for Yang-Mills and Minimal type coupling.

26 Backup Slides

27 Run I Vector Leptoquark Searches 1 st Generation Mass (GeV/c 2 ) BetaYang-Mills Minimal DØ CDF st Generation Mass (GeV/c 2 ) BetaYang-Mills Minimal DØ CDF

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