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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 Daniel Ryan Tufts University
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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
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Main Injector & Recycler Tevatron Chicago p source pp p p pp 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
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CDF ~ 200pb -1 Feb, 2002March, 2004 DØ - 175pb -1 FY '04 Projection: 230 - 310 pb -1 FY '04 Projection: 230 - 310 pb -1 CDF - 72pb -1 DØ - 104pb -1 Run I 200 100 300 400
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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
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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
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Leptoquark Production at s = 1.96 TeV 7 Daniel RyanSearches for Leptoquarks at the Tevatron Run I Run II
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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
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9 Daniel RyanSearches for Leptoquarks at the Tevatron 1 st Generation Leptoquark Searches, = 1, circa 2003
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1 st Gen. LQ's – ej ej DØ Search – 175pb -1 10 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
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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 ~(10 - 30)%
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12 Daniel RyanSearches for Leptoquarks at the Tevatron CDF – ej ej Luminosity203pb -1 Acceptance(32-42)% Background6.2 +3.1 - 2.5 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
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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 ~(18 - 37)% 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
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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...
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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 ~(13 - 25)% 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
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MET + Jets CDF Search - 191pb -1 16 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
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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)%
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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
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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
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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
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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
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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... 22 Daniel RyanSearches for Leptoquarks at the Tevatron
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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 jets, @ 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
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Summary 24 Daniel RyanSearches for Leptoquarks at the Tevatron Beta I II 1225200 1/2204 0 9898 1220202 1/2182164 0 123 1 Beta I II 1225200 1/2204 0 9898 1220202 1/2182164 0 123 1 Beta I II 1.0238200 0.5213 in progress 0.0 in progressin progress 1.0230240 0.5197 in progress 0.0117117 Beta I II 1.0238200 0.5213 in progress 0.0 in progressin progress 1.0230240 0.5197 in progress 0.0117117 1 c c 3 rd generation not shown Run 1Run 2
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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.
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Backup Slides
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Run I Vector Leptoquark Searches 1 st Generation Mass (GeV/c 2 ) BetaYang-Mills Minimal 1.0345290 DØ0.5337282 0.0 298 238 1.0330280 CDF0.5310265 0.0 1 st Generation Mass (GeV/c 2 ) BetaYang-Mills Minimal 1.0345290 DØ0.5337282 0.0 298 238 1.0330280 CDF0.5310265 0.0
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