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António Onofre (onofre@lipc.fis.uc.pt)

Testing the SM in tt and single top production. António Onofre (onofre@lipc.fis.uc.pt). On behalf of the ATLAS+CMS Collaborations. Moscow July 26 – Au gust 2, 2006 XXXIII International Conference on High Energy Physics. 1) tt @ LHC. tt Cross section Top spin correlations

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António Onofre (onofre@lipc.fis.uc.pt)

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  1. Testing the SM in tt and single top production António Onofre (onofre@lipc.fis.uc.pt) On behalf of the ATLAS+CMS Collaborations Moscow July 26 –August 2, 2006 XXXIII International Conference on High Energy Physics

  2. 1) tt @ LHC • tt Cross section • Top spin correlations • Probing the Wtb vertex • FCNC top decays 28 July 2006 Moscow, ICHEP 2006 Outline 2) Single top @ LHC: • Production Cross section 3) Conclusions

  3. “t-quarks are produced and decay as free particles” thad = LQCD-1 >> tdecay NO top hadrons 28 July 2006 Moscow, ICHEP 2006 What do we know about the top quark? • The top quark completes the three family structure of the SM • Its massive • Spin=1/2, • Charge=+2/3, • Isospin=+1/2 • tbW • Large G=1.42GeV (mb,MW,as,EW corr.) Short lifetime dm/m <2% Not directly -4/3 excluded @ 94%C.L.(D0) Not directly ~100% ct<52.5mm @95%C.L.(CDF) The TEVATRON is probing better than ever the top sector… The LHC will allow precision measurements of Top Quark Physics

  4. 1) tt @ LHC • tt cross section + (90%) (10%) W (had) ≥4 jets (DR=0.4) pT>40 GeV t (had) pT>20 GeV 2 b-jets t (lep) pT>20 GeV 28 July 2006 Moscow, ICHEP 2006 Production X-section: s ~ 833pb @ 14TeV Semileptonic Topology: Golden Channel Clean Topology: tt back to back Used for several studies

  5. 1) tt @ LHC • tt cross section mt (had) s =10.6GeV Systematic Errors: Comb. 28 July 2006 Moscow, ICHEP 2006 Selected 87000 signal events for L=10fb-1 (S/B~78, ~12 with tback) (e=3.5%) Althougherrors are dominated by systematics It seems possibleto determine mt @ 1GeV level (with L=10fb-1)

  6. 1) tt @ LHC • tt cross section A) Semi-leptonic channel (ttbbqqmnl): L=10fb-1 Dstt/stt= 9.7%(syst)±0.4%(stat)±3%(lum) B) Di-leptonic channel (ttbb lnllnl): L=10fb-1 Dstt/stt= 11%(syst)±0.9%(stat)±3%(lum) • Syst.(dominant):PDF(5%),btag(4%),JES(4%) • Back (dominant): ttll.(Wtnt, tleptons) • e = 5% (S/B=5.5) With Tau leptons (ttbb tnt lnl, t hadrons): Dstt/stt= 16%(syst)±1.3%(stat)±3%(lum) [ e=2%, S/B~1, et-tag=30% ] C) Fully Hadronic channel: L=1fb-1 e=2%, S/B<1/9 (QCD) Sys: JES(11%), PileUp(10%) Dstt/stt= 20%(syst)±3%(stat)±5%(lum) 28 July 2006 Moscow, ICHEP 2006 CERN/LHCC 2006-021 CMS TDR 8.2 • Syst.(dominant): • btag(7%), PDF(3.4%), PileUp(3.2%) • Back.(dominant):tt,W+jets • e = 6.3%

  7. 1) tt @ LHC Testing the tt Production X-section: Although t and t are produced unpolarized their spins are correlated A= q s(tLtL) + s(tRtR) - s(tLtR) - s(tRtL) s(tLtL) + s(tRtR) + s(tLtR) + s(tRtL) flq 1 dN 1 ( 1 – ADaXaX´cosf ) = N dcosf2 l+,n t t 28 July 2006 Moscow, ICHEP 2006 • Top Spin Correlations SM: New Physics affects A Other angular distributions: aX=spin analysing power of X SM:

  8. 1) tt @ LHC t q ql,n l,n qq SM Mtt<550 GeV Error (±stat ±syst) (Eur.Phys.J.C44S2 2005 13-33) • Semileptonic + Dileptonic • Syst (Eb-jet,mtop,FSR) • ~4% precision A 0.42 0.014 0.023 Ãxx´ AD -0.29 0.008 0.010 t A N(cosf > 0) - N(cosf < 0) 1 = - ADaXax´ N(cosf > 0) + N(cosf < 0) 2 28 July 2006 Moscow, ICHEP 2006 • Top Spin Correlations L=10fb-1 A) Spin correlations and angular distributions: (CERN/LHCC 2006-021, CMS TDR 8.2) B) Spin Asymmetries can also be used (X-check) (for L=10fb-1precision A,AD below 10% ) (hep-ex/0605190, subm. to Eur.Phys.J.C)

  9. 1) tt @ LHC (Eur.Phys.J.C44S2 2005 13-33) L=10fb-1 SM Error (±stat ±syst) (1/G)dG/dcos(ql*) (Mt=175 GeV) Semilep. + Dileptonic F0 0.703  0.004  0.015 FL 0.297  0.003  0.024 FR 0.000 (mb=0)  0.003  0.012 • Syst ( Eb-jet,mtop,FSR ) • dF0/F0~ 2%;dFR ~ 0.01 cos(ql*) 28 July 2006 Moscow, ICHEP 2006 • Probing the Wtb vertex A) Test the tbW decay vertex Measure W polarization(F0, FL, FR) through lepton angular distribution in W cm system:

  10. 1) tt @ LHC A- AFB A+ AFB [t=0] A± [t= (22/3-1)] ± cos(ql*) 28 July 2006 Moscow, ICHEP 2006 • Probing the Wtb vertex B) Anomalous Couplings in the tbW decay (PRD67 (2003) 014009, mb≠0) Angular Asymmetries: AFB, A+ and A- SM(LO):

  11. 1) tt @ LHC SM(LO): rL=0.423 rR=0.0005 (mb≠0) 1s Results: 28 July 2006 Moscow, ICHEP 2006 • Probing the Wtb vertex L=10fb-1 B) Anomalous Couplings in the tbW decay

  12. 1) tt @ LHC At LHC Look for: 28 July 2006 Moscow, ICHEP 2006 • FCNC in top quark decays • The top quarkalmostalways decays to a b quark,B(tWb)~1 • B(tWs)<0.18%, B(tWd)<0.02% (other decays are really rare) hep-ph/0409342 APPB35(2004)2695 FCNC decays are highly suppressed in the SM:

  13. 1) tt @ LHC L=10fb-1 L=10fb-1 28 July 2006 Moscow, ICHEP 2006 B) In the absence of signal: • FCNC top decays ATLAS: Br(tqg@95%CL)<0.14% A) 5s Sensitivity:  With 10 fb-1 already two orders of magnitude better than LEP/HERA/TEVATRON

  14. Vtb Vtb Vtb Vtb Wt-channel t-channel s ~ 250 pb s ~70pb W* (s-channel) s ~ 10 pb 28 July 2006 Moscow, ICHEP 2006 2) Single top @ LHC • Production Cross Section Three different Processes (never observed yet) Powerfull Probe of Vtb ( dVtb/Vtb~few% @ LHC ) [ PRD 70 (2004) 114012, PL B524 2002 283-288 ] Theoretical uncertainties: • Quark-gluon luminosity inside b-quark (PDF) • Renormalization scale (m) • top mass(Dmtop=4.3GeV  s(W*) changed by 3%) Probe New Physics Differently:ex. FCNC affects more t-channel ex. W´ affects more s-channel [ PRD63 (2001) 014018 ]

  15. 1 lepton, pT>25GeV/c High Missing ET 2 jets (at least 1 b-jet) Common feature: Stat: 7000 events (S/B=3) Syst: dominated by Eb-jet and Lum. Error Back: tt, Wbb and W+jets t-channel: (Nj=2,Nb=1) ( ds/s <1.5%) Stat: e~1% (S/B=15%) Wt-channel: ( ds/s ~ 4%) (Nj=3,Nb=1) Stat:1200events for tb (S/B=10%) Syst: Eb-jet, Lum. Error, back X-section s-channel: (Nj=2,Nb=2) ( ds/s ~7-8%) • t-channel: Ds/s= 8%(syst)±2.7%(stat)±5%(lum) • Wt-channel: Ds/s= 23.9%(syst)±8.8%(stat)±9.9%(MC) • s-channel: Ds/s= 31%(syst)±18%(stat)±5%(lum) 28 July 2006 Moscow, ICHEP 2006 2) Single top @ LHC • Production Cross Section (ATL-COM-PHYS-2006-002) L=30fb-1 Separate Channels by (Nj,Nb) in final state: (ATL-PHYS-PUB-2006-014) L=10fb-1 (CERN/LHCC 2006-021, CMS TDR 8.2)

  16. 28 July 2006 Moscow, ICHEP 2006 3) Conclusions • The LHC will be a top factory (8 million events already with 10fb-1) • New era on precision Top Quark Physics will start with the LHC: couplings, asymmetries, decays, etc. will be measured with unprecedented precision • Stay tuned for next year

  17. 28 July 2006 Moscow, ICHEP 2006 Backup Slides

  18. σ(W→lν) σ(tt) mt=175 GeV • s(pp tt): g g 10% 90% 28 July 2006 Moscow, ICHEP 2006 Cross-sections at the LHC • High Collision Rate • LHC (Tevatron) – every 25ns (396ns) • High Cross-Sections ~0.1b • 2-3 interactions per collision • LHC low/high lumi L=1033cm-2s-1 • 20 interactions per collision • LHC design/high lumi L=1034cm-2s-1 • W, Z, top are rare events • Requires High Luminosity • Trigger is crucial: sel. Leptons High pT

  19. Electromagnetic Calo Pb-liquid argon s/E ~ 10%/E ~1% uniform • Hadronic Calo Fe-scint Tile Calo (10l) s/E ~ 50%/E  0.03 • Muon Detectors • MAGNETS s/pT< 10 % at 1 TeV Toroide+Solenoid (4 magnets) in inner cavity Calorimeters outside field • Tracker Si pixels + strips TRD alows particle ID Solenoid B=2T s/pT~ 5x10-4 pT  0.01 28 July 2006 Moscow, ICHEP 2006 ATLAS Experiment

  20. tt @ LHC • tt cross section and top mass W=highest pT,2j (in thad system) 3-jet invariant mass electron+muon estimate for L=100 pb-1 Events / 4.15 GeV ATLAS preliminary thad=highest pT,3j Top-combinatorialand W+jets background Mjjj (GeV) 28 July 2006 Moscow, ICHEP 2006 With onlyL=100pb-1 (few days of nominal low-lumi LHC operation) No b-tag and MW cut (e=5.3%) We can easily see top peak without b-tag requirement

  21. 28 July 2006 Moscow, ICHEP 2006 ATLAS Experiment Time until Friday, August 31, 2007

  22. Electromagnetic Calo PbWO4 Crystals s/E ~ 2-5%/E no longitudinal segmentation • Hadronic Calo Brass-scint. (> 5.8 l) s/E ~ 100%/E  0.05 • Muon Detectors • MAGNET s/pT ~ 5% at 1 TeV combining with tracker 1 Solenoid (B=4T) Calorimeters inside field 28 July 2006 Moscow, ICHEP 2006 CMS Experiment • Tracker Si pixels + strips No particle ID s/pT ~ 1.5x10-4 pT  0.005

  23. 1s-bands ( sSM ) L=10fb-1 CERN/LHCC 2006-021 CMS TDR 8.2 L=10fb-1 • t-channel: Ds/s ~10%(tot) • s-channel: Ds/s ~36%(tot) 28 July 2006 Moscow, ICHEP 2006 Single top @ LHC • Sensitivity to New Physics Tait,Yuan PRD63 (2001) 014018

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